Manuale di PostGIS 3.2.0dev

DEV (Mon 26 Jul 2021 09:27:39 PM UTC rev. ff9de2c )

Il gruppo di sviluppo di PostGIS

Abstract

PostGIS è un'estensione del database object-relational PostgreSQL che consente l'archiviazione di oggetti GIS (Geographic Information Systems). PostGIS comprende il supporto per gli indici spaziali R-Tree basati su GIST, e funzioni per l'analisi e l'elaborazione di oggetti GIS.

Questo è il manuale per la versione 3.2.0dev

Questa opera è rilasciata con una licenza Creative Commons Attribution-Share Alike 3.0 License. Siete liberi di utilizzare questo materiale come volete, ma vi chiediamo di citare il progetto PostGIS come fonte e, ove possibile, di inserire un link a http://postgis.net.


Table of Contents
1. Introduzione
1.1. Comitato di Coordinamento del Progetto
1.2. Principali collaboratori attuali
1.3. Principali collaboratori passati
1.4. Altri collaboratori
2. Installazione PostGIS
2.1. Versione sintetica
2.2. Compiling and Install from Source
2.2.1. Reperire il codice sorgente
2.2.2. Install Requirements
2.2.3. Configurazione
2.2.4. Compilazione
2.2.5. Compilazione e installazione delle estensioni PostGIS
2.2.6. Testing
2.2.7. Installazione
2.3. Installing and Using the address standardizer
2.3.1. Installing Regex::Assemble
2.4. Installare o aggiornare il Geocode per Tiger e caricare i dati
2.4.1. Tiger Geocoder Enabling your PostGIS database: Using Extension
2.4.2. Tiger Geocoder Enabling your PostGIS database: Not Using Extensions
2.4.3. Using Address Standardizer Extension with Tiger geocoder
2.4.4. Caricamento dei dati Tiger
2.4.5. Aggiornamento del installazione del Geocoder Tiger
2.5. Common Problems during installation
3. PostGIS Administration
3.1. Performance Tuning
3.1.1. Startup
3.1.2. Runtime
3.2. Configuring raster support
3.3. Creating spatial databases
3.3.1. Spatially enable database using EXTENSION
3.3.2. Spatially enable database without using EXTENSION (discouraged)
3.3.3. Create a spatially-enabled database from a template
3.4. Upgrading spatial databases
3.4.1. Soft upgrade
3.4.2. Hard upgrade
4. Data Management
4.1. Spatial Data Model
4.1.1. OGC Geometry
4.1.2. SQL/MM Part 3 - Curves
4.1.3. WKT and WKB
4.2. Geometry Data Type
4.2.1. PostGIS EWKB and EWKT
4.3. Geography Data Type
4.3.1. Geography Basics
4.3.2. When to use the Geography data type
4.3.3. Geography Advanced FAQ
4.4. Spatial Tables
4.4.1. Creating a Spatial Table
4.4.2. GEOMETRY_COLUMNS View
4.4.3. Manually Registering Geometry Columns
4.5. Spatial Reference Systems
4.5.1. SPATIAL_REF_SYS Table
4.5.2. User-Defined Spatial Reference Systems
4.6. Geometry Validation
4.7. Loading Spatial Data
4.7.1. Using SQL to Load Data
4.7.2. Using the Shapefile Loader
4.8. Extracting Spatial Data
4.8.1. Using SQL to Extract Data
4.8.2. Using the Shapefile Dumper
4.9. Building Spatial Indexes
4.9.1. GiST Indexes
4.9.2. BRIN Indexes
4.9.3. SP-GiST Indexes
4.9.4. Tuning Index Usage
5. Spatial Queries
5.1. Determining Spatial Relationships
5.1.1. Dimensionally Extended 9-Intersection Model
5.1.2. Named Spatial Relationships
5.1.3. General Spatial Relationships
5.2. Using Spatial Indexes
5.3. Examples of Spatial SQL
6. Consigli per migliori prestazioni
6.1. Piccole tabelle contenenti geometrie di grandi dimensioni
6.1.1. Descrizione del problema
6.1.2. Possibili soluzioni
6.2. CLUSTERing di indici geometrici
6.3. Evitare la conversione della dimensione
7. Building Applications
7.1. Using MapServer
7.1.1. Basic Usage
7.1.2. Frequently Asked Questions
7.1.3. Advanced Usage
7.1.4. Examples
7.2. Java Clients (JDBC)
7.3. C Clients (libpq)
7.3.1. Text Cursors
7.3.2. Binary Cursors
8. Guida a PostGIS
8.1. PostgreSQL PostGIS tipi Geometry/Geography/Box
8.2. Funzioni per la gestione del database
8.3. Costruttori geometrici.
8.4. Geometry Accessors
8.5. Geometry Editors
8.6. Geometry Validation
8.7. Spatial Reference System Functions
8.8. Geometry Input
8.8.1. Well-Known Text (WKT)
8.8.2. Well-Known Binary (WKB)
8.8.3. Other Formats
8.9. Geometry Output
8.9.1. Well-Known Text (WKT)
8.9.2. Well-Known Binary (WKB)
8.9.3. Other Formats
8.10. Operatori
8.10.1. Bounding Box Operators
8.10.2. Operatori
8.11. Spatial Relationships
8.11.1. Topological Relationships
8.11.2. Distance Relationships
8.12. Measurement Functions
8.13. Overlay Functions
8.14. Geometry Processing
8.15. Affine Transformations
8.16. Clustering Functions
8.17. Bounding Box Functions
8.18. Sistemi di riferimento lineare
8.19. Trajectory Functions
8.20. SFCGAL Functions
8.21. Long Transaction Support
8.22. Version Functions
8.23. Grand Unified Custom Variables (GUCs)
8.24. Troubleshooting Functions
9. Domande frequenti (F.A.Q) su PostGIS
10. Topologia
10.1. Tipi di dato topologici
10.2. Topology Domains
10.3. Topology and TopoGeometry Management
10.4. Topology Statistics Management
10.5. Topology Constructors
10.6. Topology Editors
10.7. Topology Accessors
10.8. Topology Processing
10.9. TopoGeometry Constructors
10.10. TopoGeometry Editors
10.11. TopoGeometry Accessors
10.12. TopoGeometry Outputs
10.13. Topology Spatial Relationships
11. Dati raster: gestione, interrogazione e applicazioni
11.1. Caricare e creare raster
11.1.1. Usare raster2pgsql per caricare i raster
11.1.2. Creazione di raster tramite le funzioni raster di PostGIS
11.1.3. Usare raster2pgsql per caricare i raster
11.2. Cataloghi raster
11.2.1. Catalogo delle colonne raster
11.2.2. Raster Overviews
11.3. Costruire applicazioni personalizzate con PostGIS Raster
11.3.1. Esempio di output in PHP, utilizzando ST_AsPNG assieme ad altre funzioni raster
11.3.2. Esempio ASP.NET C# di output con ST_AsPNG, assieme ad altre funzioni raster
11.3.3. app per Java console per esportare una query raster come file immagine
11.3.4. Utilizzare PLPython per esportare immagini tramite SQL
11.3.5. Produrre raster con PSQL
12. Raster Reference
12.1. Raster Support Data types
12.2. Raster Management
12.3. Raster Constructors
12.4. Raster Accessors
12.5. Raster Band Accessors
12.6. Raster Pixel Accessors and Setters
12.7. Raster Editors
12.8. Raster Band Editors
12.9. Raster Band Statistics and Analytics
12.10. Raster Inputs
12.11. Raster Outputs
12.12. Raster Processing: Map Algebra
12.13. Built-in Map Algebra Callback Functions
12.14. Raster Processing: DEM (Elevation)
12.15. Raster Processing: Raster to Geometry
12.16. Raster Operators
12.17. Raster and Raster Band Spatial Relationships
12.18. Raster Tips
12.18.1. Out-DB Rasters
13. Domande frequenti su PostGIS raster
14. PostGIS Extras
14.1. Address Standardizer
14.1.1. How the Parser Works
14.1.2. Address Standardizer Types
14.1.3. Address Standardizer Tables
14.1.4. Address Standardizer Functions
14.2. Tiger Geocoder
15. PostGIS Special Functions Index
15.1. PostGIS Aggregate Functions
15.2. PostGIS Window Functions
15.3. PostGIS SQL-MM Compliant Functions
15.4. PostGIS Geography Support Functions
15.5. PostGIS Raster Support Functions
15.6. PostGIS Geometry / Geography / Raster Dump Functions
15.7. PostGIS Box Functions
15.8. PostGIS Functions that support 3D
15.9. PostGIS Curved Geometry Support Functions
15.10. PostGIS Polyhedral Surface Support Functions
15.11. PostGIS Function Support Matrix
15.12. New, Enhanced or changed PostGIS Functions
15.12.1. PostGIS Functions new or enhanced in 3.2
15.12.2. PostGIS Functions new or enhanced in 3.1
15.12.3. PostGIS Functions new or enhanced in 3.0
15.12.4. PostGIS Functions new or enhanced in 2.5
15.12.5. PostGIS Functions new or enhanced in 2.4
15.12.6. PostGIS Functions new or enhanced in 2.3
15.12.7. PostGIS Functions new or enhanced in 2.2
15.12.8. PostGIS functions breaking changes in 2.2
15.12.9. PostGIS Functions new or enhanced in 2.1
15.12.10. PostGIS functions breaking changes in 2.1
15.12.11. PostGIS Functions new, behavior changed, or enhanced in 2.0
15.12.12. PostGIS Functions changed behavior in 2.0
15.12.13. PostGIS Functions new, behavior changed, or enhanced in 1.5
15.12.14. PostGIS Functions new, behavior changed, or enhanced in 1.4
15.12.15. PostGIS Functions new in 1.3
16. Segnalare Problemi
16.1. Segnalare Bug del Software
16.2. Segnalare Problemi nella Documentazione
A. Appendix
A.1. Release 3.1.0beta1
A.2. Release 3.1.0alpha3
A.3. Release 3.1.0alpha2
A.4. Release 3.1.0alpha1
A.5. Release 3.0.0
A.6. Release 3.0.0rc2
A.7. Release 3.0.0rc1
A.8. Release 3.0.0beta1
A.9. Release 3.0.0alpha4
A.10. Release 3.0.0alpha3
A.11. Release 3.0.0alpha2
A.12. Release 3.0.0alpha1
A.13. Release 2.5.0
A.14. Release 2.4.5
A.15. Release 2.4.4
A.16. Release 2.4.3
A.17. Release 2.4.2
A.18. Release 2.4.1
A.19. Release 2.4.0
A.20. Release 2.3.3
A.21. Release 2.3.2
A.22. Release 2.3.1
A.23. Release 2.3.0
A.24. Release 2.2.2
A.25. Release 2.2.1
A.26. Release 2.2.0
A.27. Release 2.1.8
A.28. Release 2.1.7
A.29. Release 2.1.6
A.30. Release 2.1.5
A.31. Release 2.1.4
A.32. Release 2.1.3
A.33. Release 2.1.2
A.34. Release 2.1.1
A.35. Release 2.1.0
A.36. Release 2.0.5
A.37. Release 2.0.4
A.38. Release 2.0.3
A.39. Release 2.0.2
A.40. Release 2.0.1
A.41. Release 2.0.0
A.42. Release 1.5.4
A.43. Release 1.5.3
A.44. Release 1.5.2
A.45. Release 1.5.1
A.46. Release 1.5.0
A.47. Release 1.4.0
A.48. Release 1.3.6
A.49. Release 1.3.5
A.50. Release 1.3.4
A.51. Release 1.3.3
A.52. Release 1.3.2
A.53. Release 1.3.1
A.54. Release 1.3.0
A.55. Release 1.2.1
A.56. Release 1.2.0
A.57. Release 1.1.6
A.58. Release 1.1.5
A.59. Release 1.1.4
A.60. Release 1.1.3
A.61. Release 1.1.2
A.62. Release 1.1.1
A.63. Release 1.1.0
A.64. Release 1.0.6
A.65. Release 1.0.5
A.66. Release 1.0.4
A.67. Release 1.0.3
A.68. Release 1.0.2
A.69. Release 1.0.1
A.70. Release 1.0.0
A.71. Release 1.0.0RC6
A.72. Release 1.0.0RC5
A.73. Release 1.0.0RC4
A.74. Release 1.0.0RC3
A.75. Release 1.0.0RC2
A.76. Release 1.0.0RC1

Chapter 1. Introduzione

PostGIS is a spatial extension for the PostgreSQL relational database that was created by Refractions Research Inc, as a spatial database technology research project. Refractions is a GIS and database consulting company in Victoria, British Columbia, Canada, specializing in data integration and custom software development.

PostGIS is now a project of the OSGeo Foundation and is developed and funded by many FOSS4G developers and organizations all over the world that gain great benefit from its functionality and versatility.

The PostGIS project development group plans on supporting and enhancing PostGIS to better support a range of important GIS functionality in the areas of OGC and SQL/MM spatial standards, advanced topological constructs (coverages, surfaces, networks), data source for desktop user interface tools for viewing and editing GIS data, and web-based access tools.

1.1. Comitato di Coordinamento del Progetto

Il comitato di coordinamento del progetto (in inglese Project Steering Commitee o PSC) coordina la direzione generale, i cicli di rilascio, la documentazione e le iniziative di divulgazione del progetto PostGIS. Inoltre il comitato fornisce supporto agli utenti, accetta e approva patch dalla comunità generale PostGIS e vota su questioni varie che coinvolgono PostGIS come l'accesso di commit per gli sviluppatori, i nuovi membri del comitato e modifiche della API.

Raúl Marín Rodríguez

MVT support, Bug fixing, Performance and stability improvements, GitHub curation, alignment of PostGIS with PostgreSQL releases

Regina Obe

Buildbot Maintenance, Windows production and experimental builds, documentation, alignment of PostGIS with PostgreSQL releases, X3D support, TIGER geocoder support, management functions.

Bborie Park

Sviluppo raster, integrazione con GDAL, loader raster, supporto agli utenti, generica soluzione di bachi, prove su vari sistemi operativi (Slackware, Mac, Windows e altri)

Darafei Praliaskouski

Index improvements, bug fixing and geometry/geography function improvements, SFCGAL, raster, GitHub curation, and Travis bot maintenance.

Paul Ramsey (Coordinatore)

Co-founder of PostGIS project. General bug fixing, geography support, geography and geometry index support (2D, 3D, nD index and anything spatial index), underlying geometry internal structures, GEOS functionality integration and alignment with GEOS releases, alignment of PostGIS with PostgreSQL releases, loader/dumper, and Shapefile GUI loader.

Sandro Santilli

Bug fixes and maintenance, buildbot maintenance, git mirror management, management functions, integration of new GEOS functionality and alignment with GEOS releases, topology support, and raster framework and low level API functions.

1.2. Principali collaboratori attuali

Jorge Arévalo

Sviluppo raster, supporto per il driver GDAL, loader

Nicklas Avén

Miglioramenti e aggiunte alla funzione di distanza (comprese le funzioni di distanza e di relazione 3D), formato di output Tiny WKB (TWKB) (in sviluppo) e supporto generale agli utenti

Dan Baston

Geometry clustering function additions, other geometry algorithm enhancements, GEOS enhancements and general user support

Olivier Courtin

Funzioni di input e ouput XML (KML,GML)/GeoJSON, supporto 3D e correzione di bug.

Martin Davis

GEOS enhancements and documentation

Björn Harrtell

MapBox Vector Tile and GeoBuf functions. Gogs testing and GitLab experimentation.

Mateusz Loskot

Supporto CMake per PostGIS, ha sviluppato il loader raster originale in python e le funzioni API raster di basso livello.

Pierre Racine

Architettura complessiva raster, prototipazione, supporto alla programmazione

1.3. Principali collaboratori passati

Mark Cave-Ayland

Prior PSC Member. Coordinated bug fixing and maintenance effort, spatial index selectivity and binding, loader/dumper, and Shapefile GUI Loader, integration of new and new function enhancements.

Chris Hodgson

Ex-membro del comitato di coordinamento. Sviluppo generale, manutenzione del sito e del buildbot, gestione dell'incubazione OSGeo

Kevin Neufeld

Ex-membro del comitato di coordinamento. Documentazione e strumenti di supporto alla documentazione, manutenzione dei buildbot, supporto avanzato per gli utenti nel newsgroup PostGIS, miglioramenti alle funzioni di manutenzione PostGIS.

Dave Blasby

Lo sviluppatore iniziale e uno dei cofondatori di PostGIS. Dave ha scritto il codice per gli oggetti lato server, il binding degli indici e molte delle funzioni analitiche lato server.

Jeff Lounsbury

Sviluppo iniziale del loader/dumper per gli Shapefile. Attualmente rappresentante di Project Owner di PostGIS.

Mark Leslie

Continuo sviluppo e manutenzione delle funzioni di base. Supporto avanzanto per le curve. Interfaccia grafica per il loader di Shapefile.

David Zwarg

Sviluppo raster (principalmente funzioni analitiche di map algebra)

1.4. Altri collaboratori

Collaboratori individuali

Alex BodnaruGerald FenoyMaxime Guillaud
Alex MayrhoferGino LucreziMaxime van Noppen
Andrea PeriGreg TroxelMichael Fuhr
Andreas Forø TollefsenGuillaume LelargeMike Toews
Andreas NeumannHaribabu KommiNathan Wagner
Anne GhislaHavard TveiteNathaniel Clay
Antoine BajoletIIDA TetsushiNikita Shulga
Artur ZakirovIngvild NystuenNorman Vine
Barbara PhillipotJackie LengPatricia Tozer
Ben JubbJames MarcaRafal Magda
Bernhard ReiterJason SmithRalph Mason
Björn EsserJeff AdamsRémi Cura
Brian HamlinJonne SavolainenRichard Greenwood
Bruce RindahlJose Carlos Martinez LlariRoger Crew
Bruno Wolff IIIJörg HabenichtRon Mayer
Bryce L. NordgrenJulien RouhaudSebastiaan Couwenberg
Carl AndersonKashif RasulSergey Fedoseev
Charlie SavageKlaus FoersterShinichi Sugiyama
Christoph BergKris JurkaShoaib Burq
Christoph Moench-TegederLaurenz AlbeSilvio Grosso
Dane SpringmeyerLars RoessigerSteffen Macke
Dave FuhryLeo HsuStepan Kuzmin
David ZwargLoic DacharyStephen Frost
David ZwargLuca S. PercichTalha Rizwan
David ZwargMaria Arias de ReynaTom Glancy
Dmitry VasilyevMarc DucobuTom van Tilburg
Eduin CarrilloMark SondheimVincent Mora
Eugene AntimirovMarkus SchaberVincent Picavet
Even RouaultMarkus WannerVolf Tomáš
Frank WarmerdamMatt Amos 
George SilvaMatthias Bay 

Sponsor aziendali

Queste sono realtà aziendali o altre istituzioni che hanno contribuito al progetto PostGIS sotto forma di tempo sviluppatore, hosting o finanziamento economico

Campagne di finanziamento diffuso

Crowd funding campaigns are campaigns we run to get badly wanted features funded that can service a large number of people. Each campaign is specifically focused on a particular feature or set of features. Each sponsor chips in a small fraction of the needed funding and with enough people/organizations contributing, we have the funds to pay for the work that will help many. If you have an idea for a feature you think many others would be willing to co-fund, please post to the PostGIS newsgroup your thoughts and together we can make it happen.

PostGIS 2.0.0 è stata la prima release con cui abbiamo tentato questa strategia. Abbiamo utilizzato PledgeBank, realizzando due campagne di successo.

postgistopology - Oltre 10 sponsor hanno contribuito con 250 USD ciascuno per realizzare la funzione TopoGeometry e per migliorare il supporto della topologia nella versione 2.0.0. E' successo.

postgis64windows - 20 e passa sponsor hanno contribuito con 100 USD ciascuno per retribuire il lavoro necessario per risolvere varie problematiche su PostGIS per Windows a 64 bit. E' successo. Ora abbiamo una versione per PostGIS 2.0.1 disponibile con lo stack builder PostgreSQL.

Librerie di supporto importanti

The GEOS geometry operations library

La libreria GDAL (Geospatial Data Abstraction Library), di Frank Warmerdam e altri viene utilizzata per far funzionare gran parte delle funzionalità raster introdotte in PostGIS 2.0.0. I miglioramenti realizzati su GDAL per consentire il supporto di PostGIS sono stati restituiti come contributo al progetto GDAL.

The PROJ cartographic projection library

Ultimo, ma non ultimo, il database PostgreSQL, il gigante sulle cui spalle sta PostGIS. Molta della velolcità e flessibilità di PostGIS non sarebbe possibile senza l'estensibilità, il grande query planner, l'indice GIST, e la varietà di caratteristiche SQL rese disponibili da PostgreSQL.

Chapter 2. Installazione PostGIS

Questo capitolo elenca i passi necessari all'installazione di PostGIS.

2.1. Versione sintetica

Per compilare, assumendo di avere tutte le dipendenze nel percorso di ricerca:

tar xvfz postgis-3.2.0dev.tar.gz
cd postgis-3.2.0dev
./configure
make
make install

Una volta installato PostGIS, bisogna abilitarlo individualmente nei database in cui si vuole usare.

2.2. Compiling and Install from Source

[Note]

Ormai molti sistemi operativi contengono pacchetti precompilati per PostgreSQL/PostGIS. In molti casi la compilazione è necessaria solamente se volete l'ultimissima versione o se siete uno dei manutentori dei pacchetti.

Questo paragrafo comprende le istruzioni generali per la compilazione. Se state compilando su Windows o su un altro sistema operativo, potete trovare istruzioni più dettagliate alle pagine PostGIS User contributed compile guides e PostGIS Dev Wiki.

I pacchetti precompilati per i vari sistemi operativi sono elencati alla pagina PostGIS Pre-built Packages

Se siete un utente Windows, potete reperire le versioni stabili tramite Stackbuilder o la pagina PostGIS Windows download. Inoltre potete scaricare le ultimissime versioni sperimentati per Windows, che vengono create una o due volte alla settimana, quando ci sono aggiornamenti interessanti. Potete utilizzare queste versioni per fare prove con le versioni in via di sviluppo di PostGIS

Il modulo PostGIS è un'estensione del server PostgreSQL. Pertanto, + indispensabile che PostGIS 3.2.0dev abbia pieno accesso agli header di PostgreSQL server per potersi compilare. Può essere compilato con versioni di PostgreSQL dalla 9.6 in su. Le versioni precedenti di PostgreSQL non sono supportate.

Vi rimandiamo alle guide per l'installazione di PostgreSQL, se questo non è stato ancora installato. http://www.postgresql.org .

[Note]

Per le funzionalità legate a GEOS, quando installate PostgresSQL è possibile che dobbiate esplicitamente linkare PostgreSQL con la libreria C++ standard:

LDFLAGS=-lstdc++ ./configure [INSERITE QUI LE VOSTRE OPZIONI]

Questa è una soluzione alla buona per l'interazione con finte eccezioni C++ con gli strumenti di sviluppo più datati. Se riscontrate problemi anomali (chiusura inattesa del server o casi simili), provate questo trucco. Ciò richiederà ovviamente di ricompilare PostgreSQL da zero.

I passaggi seguenti ripercorrono la procedura per configurare e compilare il sorgente di PostGIS. Sono scritti per utenti Linux e non funzioneranno su Windows o Mac.

2.2.1. Reperire il codice sorgente

Retrieve the PostGIS source archive from the downloads website http://postgis.net/stuff/postgis-3.2.0dev.tar.gz

wget http://postgis.net/stuff/postgis-3.2.0dev.tar.gz
tar -xvzf postgis-3.2.0dev.tar.gz

Questo passaggio creerà una cartella denominata postgis-3.2.0dev nella cartella di lavoro attuale.

In alternativa, potete eseguire un checkout del sorgente dalla repository svn http://svn.osgeo.org/postgis/trunk/ .

git clone https://git.osgeo.org/gitea/postgis/postgis.git postgis

Entrate nella cartella appena creata, postgis-3.2.0dev, per proseguire con l'installazione.

2.2.2. Install Requirements

PostGIS necessita dei seguenti requisiti per la compilazione e l'utilizzo:

Necessari

  • PostgreSQL 9.6 o versioni superiori. E' necessaria un'installazione completa di PostgreSQL (compresi gli header del server). PostgreSQL è disponibile al sito http://www.postgresql.org .

    Per una matrice di supporto completa per PostgreSQL / PostGIS e PostGIS/GEOS vi rimandiamo a http://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS

  • Compilatore GNU C (gcc). Per la compilazione possono essere utilizzati anche altri compilatori ANSI C, ma abbiamo riscontrato molti meno problemi nella compilazione con gcc.

  • GNU Make (gmake or make). Per molti sistem, GNU make è la versione di default di make. Potete controllare la versione tramite il comando make -v. Altre versioni di make potrebbero non elaborare il Makefile di PostGIS in modo corretto.

  • Proj4 reprojection library. Proj4 4.9 or above is required. The Proj4 library is used to provide coordinate reprojection support within PostGIS. Proj4 is available for download from http://trac.osgeo.org/proj/ .

  • GEOS geometry library, version 3.6 or greater, but GEOS 3.9+ is required to take full advantage of all the new functions and features. GEOS is available for download from http://trac.osgeo.org/geos/ .

  • LibXML2, versione 2.5.x superiore. LibXML2 è attualmente usata per alcune delle funzioni di importazione (ST_GeomFromGML and ST_GeomFromKML). LibXML2 può essere scaricata da http://xmlsoft.org/downloads.html.

  • JSON-C, version 0.9 or higher. JSON-C is currently used to import GeoJSON via the function ST_GeomFromGeoJson. JSON-C is available for download from https://github.com/json-c/json-c/releases/.

  • GDAL, version 2+ is required 3+ is preferred. This is required for raster support. http://trac.osgeo.org/gdal/wiki/DownloadSource.

  • Attualmente questo parametro non funzione, dato che il pacchetto si installerà solamente nella cartella di installazione di PostgreSQL. Potete visitare la pagina http://trac.osgeo.org/postgis/ticket/635 per seguire l'evoluzione di questo bug.

Opzionali

  • GDAL (pseudo optional) only if you don't want raster you can leave it out. Also make sure to enable the drivers you want to use as described in Section 3.2, “Configuring raster support”.

  • GTK (è necessario GTK+2.0, 2.8+) serve per compilare il loader shp2pgsql-gui shape. http://www.gtk.org/ .

  • SFCGAL, version 1.3.1 (or higher) could be used to provide additional 2D and 3D advanced analysis functions to PostGIS cf Section 8.20, “SFCGAL Functions”. And also allow to use SFCGAL rather than GEOS for some 2D functions provided by both backends (like ST_Intersection or ST_Area, for instance). A PostgreSQL configuration variable postgis.backend allow end user to control which backend he want to use if SFCGAL is installed (GEOS by default). Nota: SFCGAL 1.2 require at least CGAL 4.3 and Boost 1.54 (cf: https://oslandia.gitlab.io/SFCGAL/dev.html) https://gitlab.com/Oslandia/SFCGAL/.

  • In order to build the Section 14.1, “Address Standardizer” you will also need PCRE http://www.pcre.org (which generally is already installed on nix systems). Regex::Assemble perl CPAN package is only needed if you want to rebuild the data encoded in parseaddress-stcities.h. Section 14.1, “Address Standardizer” will automatically be built if it detects a PCRE library, or you pass in a valid --with-pcre-dir=/path/to/pcre during configure.

  • To enable ST_AsMVT protobuf-c library 1.1.0 or higher (for usage) and the protoc-c compiler (for building) are required. Also, pkg-config is required to verify the correct minimum version of protobuf-c. See protobuf-c. By default, Postgis will use Wagyu to validate MVT polygons faster which requires a c++11 compiler. It will use CXXFLAGS and the same compiler as the PostgreSQL installation. To disable this and use GEOS instead use the --without-wagyu during the configure step.

  • CUnit (CUnit). Serve per i collaudi di regressione. http://cunit.sourceforge.net/

  • DocBook (xsltproc) è necessario per creare la documentazione. Docbook è disponibile sul sito http://www.docbook.org/ .

  • DBLatex (dblatex) è necessario per creare la documentazione in formato PDF. DBLatex è disponibile dal sito http://dblatex.sourceforge.net/ .

  • ImageMagick (convert) viene utilizzato per generare le immagini utilizzate nella documentazione. ImageMagick è disponibile sul sito http://www.imagemagick.org/ .

2.2.3. Configurazione

Come in molte installazioni Linux, il primo passo consiste nel generare il Makefile che sarà poi utilizzato che compilare il codice sorgente. Per questo si esegue lo script da shell

./configure

Se non si specificano parametri aggiuntivi, questo comando cercherà di individuare automaticamente le componenti e le librerie necessarie per compilare il codice sorgente PostGIS sul vostro sistema. Benché questa sia la modalità di utilizzo più comune per ./configure, lo script accetta vari parametri per coloro che tengono le librerie e i programmi necessari in percorsi non standard.

La lista seguente riporta solamente i parametri usati più di frequente. Per una lista completa, utilizzate i parametri --help o --help=short.

--with-library-minor-version

Starting with PostGIS 3.0, the library files generated by default will no longer have the minor version as part of the file name. This means all PostGIS 3 libs will end in postgis-3. This was done to make pg_upgrade easier, with downside that you can only install one version PostGIS 3 series in your server. To get the old behavior of file including the minor version: e.g. postgis-3.0 add this switch to your configure statement.

--prefix=PREFIX

Questo è il percorso in cui saranno installate le librerie PostGIS e gli script SQL. Come default, questo percorso coincide con quello rilevato per l'installazione di PostgreSQL.

[Caution]

Attualmente questo parametro non funzione, dato che il pacchetto si installerà solamente nella cartella di installazione di PostgreSQL. Potete visitare la pagina http://trac.osgeo.org/postgis/ticket/635 per seguire l'evoluzione di questo bug.

--with-pgconfig=FILE

PostgreSQL fornisce una utility chiamata pg_config per consentire a estensioni quali PostGIS di individuare la cartella di installazione di PostgreSQL. Utilizzate questo parametro (--with-pgconfig=/path/to/pg_config) per specificare manualmente una particolare installazione di PostgreSQL per la quale PostGIS sarà compilato.

--with-gdalconfig=FILE

GDAL è una libreria necessaria per il supporto raster. Utilizzare il comando gdal-config per consentire all'installazione di individuare la cartella di installazione di GDAL, oppure utilizzare il parametro --with-gdalconfig=/path/to/gdal-config per indicare manualmente specifica installazione di GDAL con cui compilare PostGIS.

--with-geosconfig=FILE

GEOS, una libreria necessaria per gestire le geometrie, fornisce una utility chiamata geos-config per consentire alla procedura di installazione di individuare la cartella di installazione di GEOS. E' possibile utilizzare questo parametro (--with-geosconfig=/path/to/geos-config) per indicare manualmente una specifica installazione di GEO da utilizzare per la compilazione.

--with-xml2config=FILE

LibXML è la libreria richiesta dai comandi GeomFromKML/GML. Se la libreria è installata, viene normalmente localizzata automaticamente, ma se non è installata, o se volete utilizzare una versione specifica, dovete rimandare PostGIS a uno specifico file di configurazione xml2-config per consentire all'installazione di localizzare la cartella di installazione di LibXML. Utilizzate questo parametro ( >--with-xml2config=/path/to/xml2-config) per indicare manualmente il riferimento a una specifica installazione di LibXML per la compilazione di PostGIS.

--with-projdir=DIR

Proj4 è una libreria di riproiezione richiesta da PostGIS. Utilizzate questo parametro (--with-projdir=/path/to/projdir) per indicare manualmente una specifica cartella di installazione di Proj4 per la compilazione di PostGIS.

--with-libiconv=DIR

Cartella di installazione di iconv.

--with-jsondir=DIR

JSON-C è una libreria JSON con licenza MIR utilizzata da PostGIS per supportare ST_GeomFromJSON. Utilizzare questo parametro (--with-jsondir=/path/to/jsondir) per indicare manualmente una specifica cartella di installazione che PostGIS userà per la compilazione.

--with-pcredir=DIR

PCRE is an BSD-licensed Perl Compatible Regular Expression library required by address_standardizer extension. Use this parameter (--with-pcredir=/path/to/pcredir) to manually specify a particular PCRE installation directory that PostGIS will build against.

--with-gui

Compilare l'interfaccia grafica per l'importazione di dati (richiede GTK+2.0). Questo passaggio creerà shp2pgsql-gui, interfaccia grafica per shp2pgsql.

--without-raster

Installazione del supporto raster

--without-topology

Disable topology support. There is no corresponding library as all logic needed for topology is in postgis-3.2.0dev library.

--with-gettext=no

Normalmente PostGIS cercherà di rilevare il supporto per gettext e di utilizzarlo nella compilazione. Tuttavia, se risocontrate problemi di compatibilità che determinano interruzioni del loader, potete disabilitare il supporto con questo comando. Potete fare riferimento al ticket http://trac.osgeo.org/postgis/ticket/748 per un esempio di un caso risolto utilizzando questa particolare configurazione. NOTA: disattivanto questa opzione non vi perdete molto, dato che è utilizzata per il supporto internazionale o per le etichette nel loader, che non sono ancora ben documentate e in forma sperimentale.

--with-sfcgal=PATH

By default PostGIS will not install with sfcgal support without this switch. PATH is an optional argument that allows to specify an alternate PATH to sfcgal-config.

--without-phony-revision

Disable updating postgis_revision.h to match current HEAD of the git repository.

[Note]

Se avete ottenuto PostGIS dalla repository SVN , il primo passo consiste nell'eseguire lo script

./autogen.sh

Questo script genererà lo script configure, che a sua volta viente utilizzato per personalizzare l'installazione di PostGIS.

Se invece avete ottenuto PostGIS come file tar, non sarà necessario eseguire ./autogen.sh, dato che configure sarà già stato generato.

2.2.4. Compilazione

Una volta creato il Makefile, compilare PostGIS è semplice come eseguire

make

L'ultima linea dei messaggi in uscita dovrebbe essere "PostGIS was built successfully. Ready to install."

As of PostGIS v1.4.0, all the functions have comments generated from the documentation. If you wish to install these comments into your spatial databases later, run the command which requires docbook. The postgis_comments.sql and other package comments files raster_comments.sql, topology_comments.sql are also packaged in the tar.gz distribution in the doc folder so no need to make comments if installing from the tar ball. Comments are also included as part of the CREATE EXTENSION install.

make comments

Introdotto in PostGIS 2.0. Questa opzione genera degli opuscoli riassuntivi in formato HTML, utili come riferimento speditivo o per distribuzione agli studenti. Richiede xsltproc e genererà 4 file della cartella doc: topology_cheatsheet.html, tiger_geocoder_cheatsheet.html, raster_cheatsheet.html, postgis_cheatsheet.html

Ne potete scaricare alcuni già pronti sia in formato HTML che PDF dalla pagina PostGIS / PostgreSQL Study Guides

make cheatsheets

2.2.5. Compilazione e installazione delle estensioni PostGIS

Le estensioni di PostGIS vengono compilate e installate automaticamente se state utilizzando PostgreSQL 9.1+.

Se state compilando a partire dalla repository del sorgente, dovete prima compilare le descrizioni delle funzioni. Queste vengono create se avete docbook installato. Potete anche eseguire la compilazione manualmente tramite il comando:

make comments

Creare i file dei commenti non è necessario se state compilando a partire dal file tar, dato che questi file sono inclusi nel file tar stesso.

Se state compilando per PostgreSQL 9.1, le estensioni dovrebbero essere create automaticamente nel corso del processo di make install. Se serve, potete eseguire la compilazione a partire dalle cartelle delle estensioni, o potete copiare i file se ne avete bisogno su un altro server.

cd extensions
cd postgis
make clean
make
export PGUSER=postgres #overwrite psql variables
make check #to test before install
make install
# to test extensions
make check RUNTESTFLAGS=--extension
[Note]

make check uses psql to run tests and as such can use psql environment variables. Common ones useful to override are PGUSER,PGPORT, and PGHOST. Refer to psql environment variables

I file delle estensioni sono sempre gli stessi a pari versione di PostGIS, a prescindere dal sistema operativo, per cui non ci sono problemi a copiare i file delle estensioni da un sistema operativo a un altro, fintanto che i file binari di PostGIS sono già installati sui vostri server.

Se volete installare le estensioni manualmente su un server separato, diverso da quello di sviluppo, dovete copiare i seguenti file dalla cartella delle estensioni nella cartella PostgreSQL / share / extension della vostra installazione PostgreSQL, così come i file binari per la versione normale di PostGIS, se questi già non sono presenti sul server.

  • Questi sono i file di controllo che indicano informazioni come la versione dell'estensione da installare, se non specificata. postgis.control, postgis_topology.control.

  • Tutti i file nella cartella /sql di ciascuna estesnione. Da notare che quesi devono essere copiati nella cartella principale delle estensioni di PostgreSQL, share/extension extensions/postgis/sql/*.sql, extensions/postgis_topology/sql/*.sql

Una volta eseguita questa operazione, dovreste vedere postgis, postgis_topology come estensioni disponibili in PgAdmin -> extensions.

Se state utilizzando psql, potete verificare l'avvenuta installazione delle estensioni tramite questa query:

SELECT name, default_version,installed_version
FROM pg_available_extensions WHERE name LIKE 'postgis%' or name LIKE 'address%';

             name             | default_version | installed_version
------------------------------+-----------------+-------------------
 address_standardizer         | 3.2.0dev         | 3.2.0dev
 address_standardizer_data_us | 3.2.0dev         | 3.2.0dev
 postgis                      | 3.2.0dev         | 3.2.0dev
 postgis_raster               | 3.2.0dev         | 3.2.0dev
 postgis_sfcgal               | 3.2.0dev         |
 postgis_tiger_geocoder       | 3.2.0dev         | 3.2.0dev
 postgis_topology             | 3.2.0dev         |
(6 rows)

Se avete le estensioni installate nel database che state interrogando, vedrete questo fatto menzionato nella colonna installed_version. Se non vengono riportari record nel risultato, significa che non avete alcuna estensione installata sul server. PgAdmin III 1.14+ fornirà inoltre questa informazione nella sezione extensions dell'albero di navigazione del database e consentirà anche l'aggiornamento o la disinstallazione tramite clic del tasto destro del mouse.

Se le estensioni sono disponibili, potete installare l'estensione postgis nel database da voi scelto utilizzando l'interfaccia pgAdmin per le estensioni o eseguendo i seguenti comandi SQL:

CREATE EXTENSION postgis;
CREATE EXTENSION postgis_raster;
CREATE EXTENSION postgis_sfcgal;
CREATE EXTENSION fuzzystrmatch; --needed for postgis_tiger_geocoder
--optional used by postgis_tiger_geocoder, or can be used standalone
CREATE EXTENSION address_standardizer;
CREATE EXTENSION address_standardizer_data_us;
CREATE EXTENSION postgis_tiger_geocoder;
CREATE EXTENSION postgis_topology;

In psql you can use to see what versions you have installed and also what schema they are installed.

\connect mygisdb
\x
\dx postgis*
List of installed extensions
-[ RECORD 1 ]-------------------------------------------------
Name        | postgis
Version     | 3.2.0dev
Schema      | public
Description | PostGIS geometry, geography, and raster spat..
-[ RECORD 2 ]-------------------------------------------------
Name        | postgis_raster
Version     | 3.0.0dev
Schema      | public
Description | PostGIS raster types and functions
-[ RECORD 3 ]-------------------------------------------------
Name        | postgis_tiger_geocoder
Version     | 3.2.0dev
Schema      | tiger
Description | PostGIS tiger geocoder and reverse geocoder
-[ RECORD 4 ]-------------------------------------------------
Name        | postgis_topology
Version     | 3.2.0dev
Schema      | topology
Description | PostGIS topology spatial types and functions
[Warning]

Per le tabelle delle estensioni spatial_ref_sys, layer e topology non è possibile eseguire un backup esplicito. Il backup può essere eseguito solo quando viene fatto il backup delle corrispondenti estensioni postgis o postgis_topology, il che pare avvenga solamente quando eseguite un backup dell'intero database. Alla versione 2.0.1, quando viene eseguito il backup del database, gli unici oggetti di cui viene fatta copia sono i record srid non facenti parte di PostGIS. Pertanto non modificare gli SRID facenti parte dell'installazione, aspettandovi poi di trovare le vostre modiche nel backup. Se ci sono problemi, aprite un ticket. Neanche delle strutture delle tabelle delle estensioni viene eseguito un backup, dato che sono create con CREATE EXTENSION, e si presume che siano le stesse per una data versione dell'estensione. Questo comportamento è inserito nell'attuale modello delle estensioni, per cui non c'è molto che l'utente può fare.

If you installed 3.2.0dev, without using our wonderful extension system, you can change it to be extension based by running the below commands to package the functions in their respective extension.

CREATE EXTENSION postgis FROM unpackaged;
CREATE EXTENSION postgis_raster FROM unpackaged;
CREATE EXTENSION postgis_topology FROM unpackaged;
CREATE EXTENSION postgis_tiger_geocoder FROM unpackaged;

2.2.6. Testing

Se volete eseguire un test sul PostGIS compilato, eseguite

make check

Il comando di cui sopra eseguirà vari controlli e collaudi di regressione, utilizzando la libreria generata per un database PostgreSQL effettivo.

[Note]

Se avete configurato PostGIS utilizzando percorsi non standard per PostgreSQL, GEOS o Proj4, potreste dover aggiungere il percorso di queste librerie nella variabile di ambiente LD_LIBRARY_PATH

[Caution]

Attualmente il comando make check fa riferimento alle variabili di ambiente PATH e PGPORT nello svolgimento dei controlli - e non utilizza la versione PostgreSQL che può essere stata specificata nella configurazione con il parametro --with-pgconfig. Perciò assicuratevi che la vostra variabile PATH corrisponda all'installazione di PostgreSQL rilevata durante al configurazione, o preparatevi ad affrontare una serie di grattacapi.

Se il test è positivo, l'uscita dovrebbe essere simile alla seguente:

CUnit - A unit testing framework for C - Version 2.1-3
     http://cunit.sourceforge.net/


Suite: algorithm
  Test: test_lw_segment_side ...passed
  Test: test_lw_segment_intersects ...passed
  Test: test_lwline_crossing_short_lines ...passed
  Test: test_lwline_crossing_long_lines ...passed
  Test: test_lwline_crossing_bugs ...passed
  Test: test_lwpoint_set_ordinate ...passed
  Test: test_lwpoint_get_ordinate ...passed
  Test: test_point_interpolate ...passed
  Test: test_lwline_interpolate_points ...passed
  Test: test_lwline_interpolate_point_3d ...passed
  Test: test_lwline_clip ...passed
  Test: test_lwpoly_clip ...passed
  Test: test_lwtriangle_clip ...passed
  Test: test_lwline_clip_big ...passed
  Test: test_lwmline_clip ...passed
  Test: test_geohash_point ...passed
  Test: test_geohash_precision ...passed
  Test: test_geohash ...passed
  Test: test_geohash_point_as_int ...passed
  Test: test_isclosed ...passed
  Test: test_lwgeom_simplify ...passed
  Test: test_lw_arc_center ...passed
  Test: test_point_density ...passed
  Test: test_kmeans ...passed
  Test: test_median_handles_3d_correctly ...passed
  Test: test_median_robustness ...passed
  Test: test_lwpoly_construct_circle ...passed
  Test: test_trim_bits ...passed
  Test: test_lwgeom_remove_repeated_points ...passed
Suite: buildarea
  Test: buildarea1 ...passed
  Test: buildarea2 ...passed
  Test: buildarea3 ...passed
  Test: buildarea4 ...passed
  Test: buildarea4b ...passed
  Test: buildarea5 ...passed
  Test: buildarea6 ...passed
  Test: buildarea7 ...passed
Suite: geometry_clean
  Test: test_lwgeom_make_valid ...passed
Suite: clip_by_rectangle
  Test: test_lwgeom_clip_by_rect ...DEBUG1: lwgeom_clip_by_rect: GEOS Error: IllegalArgumentException: Invalid number of points in LinearRing found 3 - must be 0 or >= 4
passed
Suite: force_sfs
  Test: test_sfs_11 ...passed
  Test: test_sfs_12 ...passed
  Test: test_sqlmm ...passed
Suite: geodetic
  Test: test_sphere_direction ...passed
  Test: test_sphere_project ...passed
  Test: test_lwgeom_area_sphere ...passed
  Test: test_gbox_from_spherical_coordinates ...passed
  Test: test_gserialized_get_gbox_geocentric ...passed
  Test: test_clairaut ...passed
  Test: test_edge_intersection ...passed
  Test: test_edge_intersects ...passed
  Test: test_edge_distance_to_point ...passed
  Test: test_edge_distance_to_edge ...passed
  Test: test_lwgeom_distance_sphere ...passed
  Test: test_lwgeom_check_geodetic ...passed
  Test: test_gserialized_from_lwgeom ...passed
  Test: test_spheroid_distance ...passed
  Test: test_spheroid_area ...passed
  Test: test_lwpoly_covers_point2d ...passed
  Test: test_gbox_utils ...passed
  Test: test_vector_angle ...passed
  Test: test_vector_rotate ...passed
  Test: test_lwgeom_segmentize_sphere ...passed
  Test: test_ptarray_contains_point_sphere ...passed
  Test: test_ptarray_contains_point_sphere_iowa ...passed
  Test: test_gbox_to_string_truncated ...passed
Suite: geos
  Test: test_geos_noop ...passed
  Test: test_geos_subdivide ...passed
  Test: test_geos_linemerge ...passed
  Test: test_geos_offsetcurve ...passed
  Test: test_geos_offsetcurve_crash ...passed
  Test: test_geos_makevalid ...passed
Suite: clustering
  Test: basic_test ...passed
  Test: nonsequential_test ...passed
  Test: basic_distance_test ...passed
  Test: single_input_test ...passed
  Test: empty_inputs_test ...passed
  Test: multipoint_test ...passed
  Test: dbscan_test ...passed
  Test: dbscan_test_3612a ...passed
  Test: dbscan_test_3612b ...passed
  Test: dbscan_test_3612c ...passed
Suite: clustering_unionfind
  Test: test_unionfind_create ...passed
  Test: test_unionfind_union ...passed
  Test: test_unionfind_ordered_by_cluster ...passed
  Test: test_unionfind_path_compression ...passed
  Test: test_unionfind_collapse_cluster_ids ...passed
Suite: homogenize
  Test: test_coll_point ...passed
  Test: test_coll_line ...passed
  Test: test_coll_poly ...passed
  Test: test_coll_coll ...passed
  Test: test_geom ...passed
  Test: test_coll_curve ...passed
Suite: encoded_polyline_input
  Test: in_encoded_polyline_test_geoms ...passed
  Test: in_encoded_polyline_test_precision ...passed
Suite: geojson_input
  Test: in_geojson_test_srid ...passed
  Test: in_geojson_test_bbox ...passed
  Test: in_geojson_test_geoms ...passed
Suite: iterator
  Test: test_point_count ...passed
  Test: test_ordering ...passed
  Test: test_modification ...passed
  Test: test_mixed_rw_access ...passed
  Test: test_cannot_modify_read_only ...passed
  Test: test_no_memory_leaked_when_iterator_is_partially_used ...passed
Suite: twkb_input
  Test: test_twkb_in_point ...passed
  Test: test_twkb_in_linestring ...passed
  Test: test_twkb_in_polygon ...passed
  Test: test_twkb_in_multipoint ...passed
  Test: test_twkb_in_multilinestring ...passed
  Test: test_twkb_in_multipolygon ...passed
  Test: test_twkb_in_collection ...passed
  Test: test_twkb_in_precision ...passed
Suite: serialization/deserialization
  Test: test_typmod_macros ...passed
  Test: test_flags_macros ...passed
  Test: test_serialized_srid ...NOTICE: SRID value -3005 converted to the officially unknown SRID value 0
passed
  Test: test_gserialized_from_lwgeom_size ...passed
  Test: test_gbox_serialized_size ...passed
  Test: test_lwgeom_from_gserialized ...passed
  Test: test_lwgeom_count_vertices ...passed
  Test: test_on_gser_lwgeom_count_vertices ...passed
  Test: test_geometry_type_from_string ...passed
  Test: test_lwcollection_extract ...passed
  Test: test_lwgeom_free ...passed
  Test: test_lwgeom_swap_ordinates ...passed
  Test: test_f2d ...passed
  Test: test_lwgeom_clone ...passed
  Test: test_lwgeom_force_clockwise ...passed
  Test: test_lwgeom_calculate_gbox ...passed
  Test: test_lwgeom_is_empty ...passed
  Test: test_lwgeom_same ...passed
  Test: test_lwline_from_lwmpoint ...passed
  Test: test_lwgeom_as_curve ...passed
  Test: test_lwgeom_scale ...passed
  Test: test_gserialized_is_empty ...passed
  Test: test_gserialized_peek_gbox_p_no_box_when_empty ...passed
  Test: test_gserialized_peek_gbox_p_gets_correct_box ...passed
  Test: test_gserialized_peek_gbox_p_fails_for_unsupported_cases ...passed
  Test: test_gbox_same_2d ...passed
  Test: test_signum_macro ...passed
Suite: lwstroke
  Test: test_lwcurve_linearize ...passed
  Test: test_unstroke ...passed
Suite: measures
  Test: test_mindistance2d_tolerance ...passed
  Test: test_mindistance3d_tolerance ...NOTICE: One or both of the geometries is missing z-value. The unknown z-value will be regarded as "any value"
NOTICE: One or both of the geometries is missing z-value. The unknown z-value will be regarded as "any value"
passed
  Test: test_rect_tree_contains_point ...passed
  Test: test_rect_tree_intersects_tree ...passed
  Test: test_lwgeom_segmentize2d ...NOTICE: ptarray.c:448 - ptarray_segmentize2d: Too many segments required (1.000000e+101)
NOTICE: liblwgeom code interrupted
NOTICE: liblwgeom code interrupted
NOTICE: liblwgeom code interrupted
NOTICE: liblwgeom code interrupted
passed
  Test: test_lwgeom_locate_along ...passed
  Test: test_lw_dist2d_pt_arc ...passed
  Test: test_lw_dist2d_seg_arc ...passed
  Test: test_lw_dist2d_arc_arc ...passed
  Test: test_lw_arc_length ...passed
  Test: test_lw_dist2d_pt_ptarrayarc ...passed
  Test: test_lw_dist2d_ptarray_ptarrayarc ...passed
  Test: test_lwgeom_tcpa ...passed
  Test: test_lwgeom_is_trajectory ...NOTICE: Geometry is not a LINESTRING
NOTICE: Line does not have M dimension
NOTICE: Measure of vertex 1 (1) not bigger than measure of vertex 0 (1)
NOTICE: Measure of vertex 1 (0) not bigger than measure of vertex 0 (1)
NOTICE: Measure of vertex 2 (2) not bigger than measure of vertex 1 (3)
passed
  Test: test_rect_tree_distance_tree ...passed
Suite: effectivearea
  Test: do_test_lwgeom_effectivearea_lines ...passed
  Test: do_test_lwgeom_effectivearea_polys ...passed
Suite: chaikin
  Test: do_test_chaikin_lines ...passed
  Test: do_test_chaikin_polygons ...passed
Suite: filterm
  Test: do_test_filterm_single_geometries ...passed
  Test: do_test_filterm_collections ...passed
Suite: minimum_bounding_circle
  Test: basic_test ...passed
  Test: test_empty ...passed
Suite: miscellaneous
  Test: test_misc_force_2d ...passed
  Test: test_misc_simplify ...passed
  Test: test_misc_count_vertices ...passed
  Test: test_misc_area ...passed
  Test: test_misc_wkb ...passed
  Test: test_grid ...passed
  Test: test_grid_in_place ...passed
  Test: test_clone ...passed
  Test: test_lwmpoint_from_lwgeom ...passed
Suite: noding
  Test: test_lwgeom_node ...passed
Suite: encoded_polyline_output
  Test: out_encoded_polyline_test_geoms ...passed
  Test: out_encoded_polyline_test_srid ...passed
  Test: out_encoded_polyline_test_precision ...passed
Suite: geojson_output
  Test: out_geojson_test_precision ...passed
  Test: out_geojson_test_dims ...passed
  Test: out_geojson_test_srid ...passed
  Test: out_geojson_test_bbox ...passed
  Test: out_geojson_test_geoms ...passed
Suite: gml_output
  Test: out_gml_test_precision ...passed
  Test: out_gml_test_srid ...passed
  Test: out_gml_test_dims ...passed
  Test: out_gml_test_geodetic ...passed
  Test: out_gml_test_geoms ...passed
  Test: out_gml_test_geoms_prefix ...passed
  Test: out_gml_test_geoms_nodims ...passed
  Test: out_gml2_extent ...passed
  Test: out_gml3_extent ...passed
Suite: kml_output
  Test: out_kml_test_precision ...passed
  Test: out_kml_test_dims ...passed
  Test: out_kml_test_geoms ...passed
  Test: out_kml_test_prefix ...passed
Suite: svg_output
  Test: out_svg_test_precision ...passed
  Test: out_svg_test_dims ...passed
  Test: out_svg_test_relative ...passed
  Test: out_svg_test_geoms ...passed
  Test: out_svg_test_srid ...passed
Suite: x3d_output
  Test: out_x3d3_test_precision ...passed
  Test: out_x3d3_test_geoms ...passed
  Test: out_x3d3_test_option ...passed
Suite: ptarray
  Test: test_ptarray_append_point ...passed
  Test: test_ptarray_append_ptarray ...passed
  Test: test_ptarray_locate_point ...passed
  Test: test_ptarray_isccw ...passed
  Test: test_ptarray_signed_area ...passed
  Test: test_ptarray_insert_point ...passed
  Test: test_ptarray_contains_point ...passed
  Test: test_ptarrayarc_contains_point ...passed
  Test: test_ptarray_scale ...passed
Suite: printing
  Test: test_lwprint_default_format ...passed
  Test: test_lwprint_format_orders ...passed
  Test: test_lwprint_optional_format ...passed
  Test: test_lwprint_oddball_formats ...passed
  Test: test_lwprint_bad_formats ...passed
Suite: sfcgal
  Test: test_sfcgal_noop ...passed
Suite: split
  Test: test_lwline_split_by_point_to ...passed
  Test: test_lwgeom_split ...passed
Suite: stringbuffer
  Test: test_stringbuffer_append ...passed
  Test: test_stringbuffer_aprintf ...passed
Suite: surface
  Test: triangle_parse ...passed
  Test: tin_parse ...passed
  Test: polyhedralsurface_parse ...passed
  Test: surface_dimension ...passed
Suite: spatial_trees
  Test: test_tree_circ_create ...passed
  Test: test_tree_circ_pip ...passed
  Test: test_tree_circ_pip2 ...passed
  Test: test_tree_circ_distance ...passed
  Test: test_tree_circ_distance_threshold ...passed
Suite: triangulate
  Test: test_lwgeom_delaunay_triangulation ...passed
  Test: test_lwgeom_voronoi_diagram ...passed
  Test: test_lwgeom_voronoi_diagram_expected_empty ...passed
  Test: test_lwgeom_voronoi_diagram_custom_envelope ...passed
Suite: twkb_output
  Test: test_twkb_out_point ...passed
  Test: test_twkb_out_linestring ...passed
  Test: test_twkb_out_polygon ...passed
  Test: test_twkb_out_multipoint ...passed
  Test: test_twkb_out_multilinestring ...passed
  Test: test_twkb_out_multipolygon ...passed
  Test: test_twkb_out_collection ...passed
  Test: test_twkb_out_idlist ...passed
Suite: varint
  Test: test_zigzag ...passed
  Test: test_varint ...passed
  Test: test_varint_roundtrip ...passed
Suite: wkb_input
  Test: test_wkb_in_point ...passed
  Test: test_wkb_in_linestring ...passed
  Test: test_wkb_in_polygon ...passed
  Test: test_wkb_in_multipoint ...passed
  Test: test_wkb_in_multilinestring ...passed
  Test: test_wkb_in_multipolygon ...passed
  Test: test_wkb_in_collection ...passed
  Test: test_wkb_in_circularstring ...passed
  Test: test_wkb_in_compoundcurve ...passed
  Test: test_wkb_in_curvpolygon ...passed
  Test: test_wkb_in_multicurve ...passed
  Test: test_wkb_in_multisurface ...passed
  Test: test_wkb_in_malformed ...passed
Suite: wkb_output
  Test: test_wkb_out_point ...passed
  Test: test_wkb_out_linestring ...passed
  Test: test_wkb_out_polygon ...passed
  Test: test_wkb_out_multipoint ...passed
  Test: test_wkb_out_multilinestring ...passed
  Test: test_wkb_out_multipolygon ...passed
  Test: test_wkb_out_collection ...passed
  Test: test_wkb_out_circularstring ...passed
  Test: test_wkb_out_compoundcurve ...passed
  Test: test_wkb_out_curvpolygon ...passed
  Test: test_wkb_out_multicurve ...passed
  Test: test_wkb_out_multisurface ...passed
  Test: test_wkb_out_polyhedralsurface ...passed
Suite: wkt_input
  Test: test_wkt_in_point ...passed
  Test: test_wkt_in_linestring ...passed
  Test: test_wkt_in_polygon ...passed
  Test: test_wkt_in_multipoint ...passed
  Test: test_wkt_in_multilinestring ...passed
  Test: test_wkt_in_multipolygon ...passed
  Test: test_wkt_in_collection ...passed
  Test: test_wkt_in_circularstring ...passed
  Test: test_wkt_in_compoundcurve ...passed
  Test: test_wkt_in_curvpolygon ...passed
  Test: test_wkt_in_multicurve ...passed
  Test: test_wkt_in_multisurface ...passed
  Test: test_wkt_in_tin ...passed
  Test: test_wkt_in_polyhedralsurface ...passed
  Test: test_wkt_in_errlocation ...passed
  Test: test_wkt_double ...passed
Suite: wkt_output
  Test: test_wkt_out_point ...passed
  Test: test_wkt_out_linestring ...passed
  Test: test_wkt_out_polygon ...passed
  Test: test_wkt_out_multipoint ...passed
  Test: test_wkt_out_multilinestring ...passed
  Test: test_wkt_out_multipolygon ...passed
  Test: test_wkt_out_collection ...passed
  Test: test_wkt_out_circularstring ...passed
  Test: test_wkt_out_compoundcurve ...passed
  Test: test_wkt_out_curvpolygon ...passed
  Test: test_wkt_out_multicurve ...passed
  Test: test_wkt_out_multisurface ...passed
Suite: wrapx
  Test: test_lwgeom_wrapx ...passed

Run Summary:    Type  Total    Ran Passed Failed Inactive
              suites     44     44    n/a      0        0
               tests    300    300    300      0        0
             asserts   4215   4215   4215      0      n/a
Elapsed time =    0.229 seconds

PostgreSQL 12devel on x86_64-w64-mingw32, compiled by gcc.exe (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0, 64-bit
  Postgis 3.0.0dev - r17081 - 2018-11-28 18:50:02
  scripts 3.0.0dev r17081
  GEOS: 3.7.0-CAPI-1.11.0 673b9939
  PROJ: Rel. 5.2.0, September 15th, 2018

Running tests

 ../loader/Point .............. ok
 ../loader/PointM .............. ok
 ../loader/PointZ .............. ok
 ../loader/MultiPoint .............. ok
 ../loader/MultiPointM .............. ok
 ../loader/MultiPointZ .............. ok
 ../loader/Arc .............. ok
 ../loader/ArcM .............. ok
 ../loader/ArcZ .............. ok
 ../loader/Polygon .............. ok
 ../loader/PolygonM .............. ok
 ../loader/PolygonZ .............. ok
 ../loader/TSTPolygon ......... ok
 ../loader/TSIPolygon ......... ok
 ../loader/TSTIPolygon ......... ok
 ../loader/PointWithSchema ..... ok
 ../loader/NoTransPoint ......... ok
 ../loader/NotReallyMultiPoint ......... ok
 ../loader/MultiToSinglePoint ......... ok
 ../loader/ReprojectPts ........ ok
 ../loader/ReprojectPtsGeog ........ ok
 ../loader/Latin1 .... ok
 ../loader/Latin1-implicit .... ok
 ../loader/mfile .... ok
 ../dumper/literalsrid ....... ok
 ../dumper/realtable ....... ok
 affine .. ok
 bestsrid .. ok
 binary .. ok
 boundary .. ok
 chaikin .. ok
 filterm .. ok
 cluster .. ok
 concave_hull .. ok
 concave_hull_hard .. ok
 ctors .. ok
 curvetoline .. ok
 dump .. ok
 dumppoints .. ok
 empty .. ok
 estimatedextent .. ok
 forcecurve .. ok
 geography .. ok
 geometric_median .. ok
 in_geohash .. ok
 in_gml .. ok
 in_kml .. ok
 in_encodedpolyline .. ok
 iscollection .. ok
 legacy .. ok
 long_xact .. ok
 lwgeom_regress .. ok
 measures .. ok
 minimum_bounding_circle .. ok
 normalize .. ok
 operators .. ok
 orientation .. ok
 out_geometry .. ok
 out_geography .. ok
 polygonize .. ok
 polyhedralsurface .. ok
 postgis_type_name .. ok
 quantize_coordinates .. ok
 regress .. ok
 regress_bdpoly .. ok
 regress_gist_index_nd .. ok
 regress_index .. ok
 regress_index_nulls .. ok
 regress_management .. ok
 regress_selectivity .. ok
 regress_lrs .. ok
 regress_ogc .. ok
 regress_ogc_cover .. ok
 regress_ogc_prep .. ok
 regress_proj .. ok
 relate .. ok
 remove_repeated_points .. ok
 removepoint .. ok
 reverse .. ok
 setpoint .. ok
 simplify .. ok
 simplifyvw .. ok
 size .. ok
 snaptogrid .. ok
 split .. ok
 sql-mm-serialize .. ok
 sql-mm-circularstring .. ok
 sql-mm-compoundcurve .. ok
 sql-mm-curvepoly .. ok
 sql-mm-general .. ok
 sql-mm-multicurve .. ok
 sql-mm-multisurface .. ok
 swapordinates .. ok
 summary .. ok
 temporal .. ok
 tickets .. ok
 twkb .. ok
 typmod .. ok
 wkb .. ok
 wkt .. ok
 wmsservers .. ok
 knn_recheck .. ok
 temporal_knn .. ok
 hausdorff .. ok
 regress_buffer_params .. ok
 frechet .. ok
 offsetcurve .. ok
 relatematch .. ok
 isvaliddetail .. ok
 sharedpaths .. ok
 snap .. ok
 node .. ok
 unaryunion .. ok
 clean .. ok
 relate_bnr .. ok
 delaunaytriangles .. ok
 clipbybox2d .. ok
 subdivide .. ok
 voronoi .. ok
 minimum_clearance .. ok
 oriented_envelope .. ok
 in_geojson .. ok
 regress_brin_index .. ok
 regress_brin_index_3d .. ok
 regress_brin_index_geography .. ok
 regress_spgist_index_2d .. ok
 regress_spgist_index_3d .. ok
 regress_spgist_index_nd .. ok
 mvt .. ok
 geobuf .. ok
 mvt_jsonb .. ok
 uninstall .. ok (4643)

Run tests: 134
Failed: 0


-- if you build with SFCGAL

PostgreSQL 12devel on x86_64-w64-mingw32, compiled by gcc.exe (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0, 64-bit
  Postgis 3.0.0dev - r17081 - 2018-11-28 18:50:02
  scripts 3.0.0dev r17081
  GEOS: 3.7.0-CAPI-1.11.0 673b9939
  PROJ: Rel. 5.2.0, September 15th, 2018
  SFCGAL: 1.3.2

Running tests

 regress_sfcgal .. ok
 empty .. ok
 geography .. ok
 legacy .. ok
 measures .. ok
 regress_ogc_prep .. ok
 regress_ogc .. ok
 regress .. ok
 tickets .. ok
 concave_hull .. ok
 wmsservers .. ok
 approximatemedialaxis .. ok
 uninstall .. ok (4643)

Run tests: 13
Failed: 0

-- if you built with raster support



     CUnit - A unit testing framework for C - Version 2.1-2
     http://cunit.sourceforge.net/


Suite: pixtype
  Test: test_pixtype_size ...passed
  Test: test_pixtype_alignment ...passed
  Test: test_pixtype_name ...passed
  Test: test_pixtype_index_from_name ...passed
  Test: test_pixtype_get_min_value ...passed
  Test: test_pixtype_compare_clamped_values ...passed
Suite: raster_basics
  Test: test_raster_new ...passed
  Test: test_raster_empty ...passed
  Test: test_raster_metadata ...passed
  Test: test_raster_clone ...passed
  Test: test_raster_from_band ...passed
  Test: test_raster_replace_band ...passed
Suite: band_basics
  Test: test_band_metadata ...passed
  Test: test_band_pixtype_1BB ...passed
  Test: test_band_pixtype_2BUI ...passed
  Test: test_band_pixtype_4BUI ...passed
  Test: test_band_pixtype_8BUI ...passed
  Test: test_band_pixtype_8BSI ...passed
  Test: test_band_pixtype_16BUI ...passed
  Test: test_band_pixtype_16BSI ...passed
  Test: test_band_pixtype_32BUI ...passed
  Test: test_band_pixtype_32BSI ...passed
  Test: test_band_pixtype_32BF ...passed
  Test: test_band_pixtype_64BF ...passed
  Test: test_band_get_pixel_line ...WARNING: Limiting returning number values to 1
WARNING: Attempting to get pixel values with out of range raster coordinates: (5, 5)
passed
  Test: test_band_new_offline_from_path ...passed
Suite: raster_wkb
  Test: test_raster_wkb ...SRID value -1 converted to the officially unknown SRID value 0
SRID value -1 converted to the officially unknown SRID value 0
SRID value -1 converted to the officially unknown SRID value 0
SRID value -1 converted to the officially unknown SRID value 0
SRID value -1 converted to the officially unknown SRID value 0
SRID value -1 converted to the officially unknown SRID value 0
passed
Suite: gdal
  Test: test_gdal_configured ...passed
  Test: test_gdal_drivers ...passed
  Test: test_gdal_rasterize ...passed
  Test: test_gdal_polygonize ...passed
  Test: test_raster_to_gdal ...Warning 6: PNG driver doesn't support data type Float64. Only eight bit (Byte) and sixteen bit (UInt16) bands supported. Defaulting to Byte

passed
  Test: test_gdal_to_raster ...passed
  Test: test_gdal_warp ...passed
Suite: raster_geometry
  Test: test_raster_envelope ...passed
  Test: test_raster_envelope_geom ...passed
  Test: test_raster_convex_hull ...passed
  Test: test_raster_surface ...INFO: Ring Self-intersection at or near point 2 -2
INFO: Ring Self-intersection at or near point 3 -3
passed
  Test: test_raster_perimeter ...passed
  Test: test_raster_pixel_as_polygon ...passed
Suite: raster_misc
  Test: test_raster_cell_to_geopoint ...passed
  Test: test_raster_geopoint_to_cell ...passed
  Test: test_raster_from_two_rasters ...passed
  Test: test_raster_compute_skewed_raster ...passed
Suite: band_stats
  Test: test_band_stats ...passed
  Test: test_band_value_count ...passed
Suite: band_misc
  Test: test_band_get_nearest_pixel ...passed
  Test: test_band_get_pixel_of_value ...passed
  Test: test_pixel_set_to_array ...passed
Suite: mapalgebra
  Test: test_raster_iterator ...passed
  Test: test_band_reclass ...passed
  Test: test_raster_colormap ...passed
Suite: spatial_relationship
  Test: test_raster_geos_overlaps ...passed
  Test: test_raster_geos_touches ...passed
  Test: test_raster_geos_contains ...passed
  Test: test_raster_geos_contains_properly ...passed
  Test: test_raster_geos_covers ...passed
  Test: test_raster_geos_covered_by ...passed
  Test: test_raster_within_distance ...passed
  Test: test_raster_fully_within_distance ...passed
  Test: test_raster_intersects ...passed
  Test: test_raster_same_alignment ...passed
Suite: misc
  Test: test_rgb_to_hsv ...passed
  Test: test_hsv_to_rgb ...passed
  Test: test_util_gdal_open ...passed

Run Summary:    Type  Total    Ran Passed Failed Inactive
              suites     12     12    n/a      0        0
               tests     65     65     65      0        0
             asserts  45896  45896  45896      0      n/a

Elapsed time =    0.499 seconds

Loading Raster into 'postgis_reg'
PostgreSQL 12devel on x86_64-w64-mingw32, compiled by gcc.exe (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0, 64-bit
  Postgis 3.0.0dev - r17081 - 2018-11-28 18:50:02
  scripts 3.0.0dev r17081
  raster scripts 3.0.0dev r17081
  GEOS: 3.7.0-CAPI-1.11.0 673b9939
  PROJ: Rel. 5.2.0, September 15th, 2018
  GDAL: GDAL 2.3.1, released 2018/06/22

Running tests

 check_gdal .. ok
 load_outdb ... ok
 check_raster_columns .. ok
 check_raster_overviews .. ok
 rt_io .. ok
 rt_bytea .. ok
 rt_wkb .. ok
 box3d .. ok
 rt_addband .. ok
 rt_band .. ok
 rt_tile .. ok
 rt_dimensions .. ok
 rt_scale .. ok
 rt_pixelsize .. ok
 rt_upperleft .. ok
 rt_rotation .. ok
 rt_georeference .. ok
 rt_set_properties .. ok
 rt_isempty .. ok
 rt_hasnoband .. ok
 rt_metadata .. ok
 rt_rastertoworldcoord .. ok
 rt_worldtorastercoord .. ok
 rt_convexhull .. ok
 rt_envelope .. ok
 rt_band_properties .. ok
 rt_set_band_properties .. ok
 rt_pixelaspolygons .. ok
 rt_pixelaspoints .. ok
 rt_pixelascentroids .. ok
 rt_setvalues_array .. ok
 rt_summarystats .. ok
 rt_count .. ok
 rt_histogram .. ok
 rt_quantile .. ok
 rt_valuecount .. ok
 rt_valuepercent .. ok
 rt_bandmetadata .. ok
 rt_pixelvalue .. ok
 rt_neighborhood .. ok
 rt_nearestvalue .. ok
 rt_pixelofvalue .. ok
 rt_polygon .. ok
 rt_setbandpath .. ok
 rt_utility .. ok
 rt_fromgdalraster .. ok
 rt_asgdalraster .. ok
 rt_astiff .. ok
 rt_asjpeg .. ok
 rt_aspng .. ok
 rt_reclass .. ok
 rt_gdalwarp .. ok
 rt_asraster .. ok
 rt_dumpvalues .. ok
 rt_makeemptycoverage .. ok
 rt_createoverview .. ok
 rt_mapalgebraexpr .. ok
 rt_mapalgebrafct .. ok
 rt_mapalgebraexpr_2raster .. ok
 rt_mapalgebrafct_2raster .. ok
 rt_mapalgebrafctngb .. ok
 rt_mapalgebrafctngb_userfunc .. ok
 rt_intersection .. ok
 rt_clip .. ok
 rt_mapalgebra .. ok
 rt_mapalgebra_expr .. ok
 rt_mapalgebra_mask .. ok
 rt_union .. ok
 rt_invdistweight4ma .. ok
 rt_4ma .. ok
 rt_setvalues_geomval .. ok
 rt_elevation_functions .. ok
 rt_colormap .. ok
 rt_grayscale .. ok
 rt_gist_relationships .. ok
 rt_intersects .. ok
 rt_samealignment .. ok
 rt_geos_relationships .. ok
 rt_iscoveragetile .. ok
 bug_test_car5 .. ok
 permitted_gdal_drivers .. ok
 tickets .. ok
 loader/Basic .. ok
 loader/Projected ... ok
 loader/BasicCopy .. ok
 loader/BasicFilename .. ok
 loader/BasicOutDB .. ok
 loader/Tiled10x10 .. ok
 loader/Tiled10x10Copy .. ok
 loader/Tiled8x8 .. ok
 clean .. ok
 uninstall .. ok (4643)

Run tests: 101
Failed: 0

-- topology regress
PostgreSQL 12devel on x86_64-w64-mingw32, compiled by gcc.exe (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0, 64-bit
  Postgis 3.0.0dev - r17081 - 2018-11-28 18:50:02
  scripts 3.0.0dev r17081
  GEOS: 3.7.0-CAPI-1.11.0 673b9939
  PROJ: Rel. 5.2.0, September 15th, 2018

Running tests

 regress/legacy_validate .. ok
 regress/legacy_predicate .. ok
 regress/legacy_invalid .. ok
 regress/sqlmm .. ok
 regress/legacy_query .. ok
 regress/addnode .. ok
 regress/addedge .. ok
 regress/addface .. ok
 regress/addface2.5d .. ok
 regress/addtopogeometrycolumn .. ok
 regress/polygonize .. ok
 regress/st_addisoedge .. ok
 regress/st_addisonode .. ok
 regress/st_addedgemodface .. ok
 regress/st_addedgenewfaces .. ok
 regress/st_changeedgegeom .. ok
 regress/st_createtopogeo .. ok
 regress/st_getfacegeometry .. ok
 regress/st_getfaceedges .. ok
 regress/st_modedgeheal .. ok
 regress/st_modedgesplit .. ok
 regress/st_newedgeheal .. ok
 regress/st_newedgessplit .. ok
 regress/st_remedgenewface .. ok
 regress/st_remedgemodface .. ok
 regress/st_simplify .. ok
 regress/topoelement .. ok
 regress/topoelementarray_agg .. ok
 regress/topogeo_addlinestring .. ok
 regress/topogeo_addpoint .. ok
 regress/topogeo_addpolygon .. ok
 regress/topogeom_edit .. ok
 regress/topogeometry_type .. ok
 regress/topojson .. ok
 regress/topologysummary .. ok
 regress/topo2.5d .. ok
 regress/totopogeom .. ok
 regress/droptopology .. ok
 regress/droptopogeometrycolumn .. ok
 regress/copytopology .. ok
 regress/createtopogeom .. ok
 regress/createtopology .. ok
 regress/gml .. ok
 regress/getnodebypoint .. ok
 regress/getedgebypoint .. ok
 regress/getfacebypoint .. ok
 regress/getringedges .. ok
 regress/gettopogeomelements .. ok
 regress/layertrigger .. ok
 regress/validatetopology .. ok
 uninstall .. ok (4643)

Run tests: 51
Failed: 0

-- if you built --with-gui, you should see this too

     CUnit - A unit testing framework for C - Version 2.1-2
     http://cunit.sourceforge.net/


Suite: Shapefile Loader File shp2pgsql Test
  Test: test_ShpLoaderCreate() ...passed
  Test: test_ShpLoaderDestroy() ...passed
Suite: Shapefile Loader File pgsql2shp Test
  Test: test_ShpDumperCreate() ...passed
  Test: test_ShpDumperDestroy() ...passed

Run Summary:    Type  Total    Ran Passed Failed Inactive
              suites      2      2    n/a      0        0
               tests      4      4      4      0        0
             asserts      4      4      4      0      n/a

The postgis_tiger_geocoder and address_standardizer extensions, currenlty only support the standard PostgreSQL installcheck. To test these use the below. Note: the make install is not necessary if you already did make install at root of PostGIS code folder.

For address_standardizer:

cd extensions/address_standardizer
make install
make installcheck
          

Output should look like:

============== dropping database "contrib_regression" ==============
DROP DATABASE
============== creating database "contrib_regression" ==============
CREATE DATABASE
ALTER DATABASE
============== running regression test queries        ==============
test test-init-extensions     ... ok
test test-parseaddress        ... ok
test test-standardize_address_1 ... ok
test test-standardize_address_2 ... ok

=====================
 All 4 tests passed.
=====================

For tiger geocoder, make sure you have postgis and fuzzystrmatch extensions available in your PostgreSQL instance. The address_standardizer tests will also kick in if you built postgis with address_standardizer support:

cd extensions/postgis_tiger_geocoder
make install
make installcheck
          

output should look like:

============== dropping database "contrib_regression" ==============
DROP DATABASE
============== creating database "contrib_regression" ==============
CREATE DATABASE
ALTER DATABASE
============== installing fuzzystrmatch               ==============
CREATE EXTENSION
============== installing postgis                     ==============
CREATE EXTENSION
============== installing postgis_tiger_geocoder      ==============
CREATE EXTENSION
============== installing address_standardizer        ==============
CREATE EXTENSION
============== running regression test queries        ==============
test test-normalize_address   ... ok
test test-pagc_normalize_address ... ok

=====================
All 2 tests passed.
=====================

2.2.7. Installazione

Per installare PostGIS, digitate

make install

Questo comando copierà i file per l'installazione di PostGIS nelle cartelle appropriate, specificate tramite il parametro di configurazione --prefix. In particolare:

  • I file binari del loader e del dumper vengono installati in [prefix]/bin.

  • I file SQL, quali postgis.sql, vengono installati in [prefix]/share/contrib.

  • Le librerie PostGIS vengono installate in [prefix]/lib.

Se avete eseguito il comando make comments per generare i file postgis_comments.sql e raster_comments.sql, installate i file SQL eseguendo

make comments-install

[Note]

postgis_comments.sql, raster_comments.sql, e topology_comments.sql sono separati dai tipici obiettivi per il build e per l'installazione, dato che hanno una ulteriore dipendenza da xsltproc.

2.3. Installing and Using the address standardizer

The address_standardizer extension used to be a separate package that required separate download. From PostGIS 2.2 on, it is now bundled in. For more information about the address_standardize, what it does, and how to configure it for your needs, refer to Section 14.1, “Address Standardizer”.

This standardizer can be used in conjunction with the PostGIS packaged tiger geocoder extension as a replacement for the Normalize_Address discussed. To use as replacement refer to Section 2.4.3, “Using Address Standardizer Extension with Tiger geocoder”. You can also use it as a building block for your own geocoder or use it to standardize your addresses for easier compare of addresses.

The address standardizer relies on PCRE which is usually already installed on many Nix systems, but you can download the latest at: http://www.pcre.org. If during Section 2.2.3, “Configurazione”, PCRE is found, then the address standardizer extension will automatically be built. If you have a custom pcre install you want to use instead, pass to configure --with-pcredir=/path/to/pcre where /path/to/pcre is the root folder for your pcre include and lib directories.

For Windows users, the PostGIS 2.1+ bundle is packaged with the address_standardizer already so no need to compile and can move straight to CREATE EXTENSION step.

Once you have installed, you can connect to your database and run the SQL:

CREATE EXTENSION address_standardizer;

The following test requires no rules, gaz, or lex tables

SELECT num, street, city, state, zip
 FROM parse_address('1 Devonshire Place PH301, Boston, MA 02109');

Output should be

num |         street         |  city  | state |  zip
-----+------------------------+--------+-------+-------
 1   | Devonshire Place PH301 | Boston | MA    | 02109

2.3.1. Installing Regex::Assemble

Perl Regex:Assemble is no longer needed for compiling address_standardizer extension since the files it generates are part of the source tree. However if you need to edit the usps-st-city-orig.txt or usps-st-city-orig.txt usps-st-city-adds.tx, you need to rebuild parseaddress-stcities.h which does require Regex:Assemble.

cpan Regexp::Assemble

or if you are on Ubuntu / Debian you might need to do

sudo perl -MCPAN -e "install Regexp::Assemble"

2.4. Installare o aggiornare il Geocode per Tiger e caricare i dati

Extras like Tiger geocoder may not be packaged in your PostGIS distribution. If you are missing the tiger geocoder extension or want a newer version than what your install comes with, then use the share/extension/postgis_tiger_geocoder.* files from the packages in Windows Unreleased Versions section for your version of PostgreSQL. Although these packages are for windows, the postgis_tiger_geocoder extension files will work on any OS since the extension is an SQL/plpgsql only extension.

2.4.1. Tiger Geocoder Enabling your PostGIS database: Using Extension

If you are using PostgreSQL 9.1+ and PostGIS 2.1+, you can take advantage of the new extension model for installing tiger geocoder. To do so:

  1. First get binaries for PostGIS 2.1+ or compile and install as usual. This should install the necessary extension files as well for tiger geocoder.

  2. Connect to your database via psql or pgAdmin or some other tool and run the following SQL commands. Note that if you are installing in a database that already has postgis, you don't need to do the first step. If you have fuzzystrmatch extension already installed, you don't need to do the second step either.

    CREATE EXTENSION postgis;
    CREATE EXTENSION fuzzystrmatch;
    CREATE EXTENSION postgis_tiger_geocoder;
    --this one is optional if you want to use the rules based standardizer (pagc_normalize_address)
    CREATE EXTENSION address_standardizer;

    If you already have postgis_tiger_geocoder extension installed, and just want to update to the latest run:

    ALTER EXTENSION postgis UPDATE;
    ALTER EXTENSION postgis_tiger_geocoder UPDATE;

    If you made custom entries or changes to tiger.loader_platform and tiger.loader_variables you may need to update these.

  3. To confirm your install is working correctly, run this sql in your database:

    SELECT na.address, na.streetname,na.streettypeabbrev, na.zip
            FROM normalize_address('1 Devonshire Place, Boston, MA 02109') AS na;

    Which should output

    address | streetname | streettypeabbrev |  zip
    ---------+------------+------------------+-------
               1 | Devonshire | Pl               | 02109
  4. Create a new record in tiger.loader_platform table with the paths of your executables and server.

    So for example to create a profile called debbie that follows sh convention. You would do:

    INSERT INTO tiger.loader_platform(os, declare_sect, pgbin, wget, unzip_command, psql, path_sep,
                       loader, environ_set_command, county_process_command)
    SELECT 'debbie', declare_sect, pgbin, wget, unzip_command, psql, path_sep,
               loader, environ_set_command, county_process_command
      FROM tiger.loader_platform
      WHERE os = 'sh';

    And then edit the paths in the declare_sect column to those that fit Debbie's pg, unzip,shp2pgsql, psql, etc path locations.

    If you don't edit this loader_platform table, it will just contain common case locations of items and you'll have to edit the generated script after the script is generated.

  5. As of PostGIS 2.4.1 the Zip code-5 digit tabulation area zcta5 load step was revised to load current zcta5 data and is part of the Loader_Generate_Nation_Script when enabled. It is turned off by default because it takes quite a bit of time to load (20 to 60 minutes), takes up quite a bit of disk space, and is not used that often.

    To enable it, do the following:

    UPDATE tiger.loader_lookuptables SET load = true WHERE table_name = 'zcta510';

    If present the Geocode function can use it if a boundary filter is added to limit to just zips in that boundary. The Reverse_Geocode function uses it if the returned address is missing a zip, which often happens with highway reverse geocoding.

  6. Create a folder called gisdata on root of server or your local pc if you have a fast network connection to the server. This folder is where the tiger files will be downloaded to and processed. If you are not happy with having the folder on the root of the server, or simply want to change to a different folder for staging, then edit the field staging_fold in the tiger.loader_variables table.

  7. Create a folder called temp in the gisdata folder or whereever you designated the staging_fold to be. This will be the folder where the loader extracts the downloaded tiger data.

  8. Then run the Loader_Generate_Nation_Script SQL function make sure to use the name of your custom profile and copy the script to a .sh or .bat file. So for example to build the nation load:

    psql -c "SELECT Loader_Generate_Nation_Script('debbie')" -d geocoder -tA > /gisdata/nation_script_load.sh
  9. Run the generated nation load commandline scripts.

    cd /gisdata
    sh nation_script_load.sh
  10. After you are done running the nation script, you should have three tables in your tiger_data schema and they should be filled with data. Confirm you do by doing the following queries from psql or pgAdmin

    SELECT count(*) FROM tiger_data.county_all;
    count
    -------
      3233
    (1 row)
    SELECT count(*) FROM tiger_data.state_all;
    count
    -------
        56
    (1 row)
    
  11. By default the tables corresponding to bg, tract, tabblock are not loaded. These tables are not used by the geocoder but are used by folks for population statistics. If you wish to load them as part of your state loads, run the following statement to enable them.

    UPDATE tiger.loader_lookuptables SET load = true WHERE load = false AND lookup_name IN('tract', 'bg', 'tabblock');

    Alternatively you can load just these tables after loading state data using the Loader_Generate_Census_Script

  12. For each state you want to load data for, generate a state script Loader_Generate_Script.

    [Warning]

    DO NOT Generate the state script until you have already loaded the nation data, because the state script utilizes county list loaded by nation script.

  13. psql -c "SELECT Loader_Generate_Script(ARRAY['MA'], 'debbie')" -d geocoder -tA > /gisdata/ma_load.sh
  14. Run the generated commandline scripts.

    cd /gisdata
    sh ma_load.sh
  15. After you are done loading all data or at a stopping point, it's a good idea to analyze all the tiger tables to update the stats (include inherited stats)

    SELECT install_missing_indexes();
    vacuum (analyze, verbose) tiger.addr;
    vacuum (analyze, verbose) tiger.edges;
    vacuum (analyze, verbose) tiger.faces;
    vacuum (analyze, verbose) tiger.featnames;
    vacuum (analyze, verbose) tiger.place;
    vacuum (analyze, verbose) tiger.cousub;
    vacuum (analyze, verbose) tiger.county;
    vacuum (analyze, verbose) tiger.state;
    vacuum (analyze, verbose) tiger.zip_lookup_base;
    vacuum (analyze, verbose) tiger.zip_state;
    vacuum (analyze, verbose) tiger.zip_state_loc;

2.4.1.1. Converting a Tiger Geocoder Regular Install to Extension Model

If you installed the tiger geocoder without using the extension model, you can convert to the extension model as follows:

  1. Follow instructions in Section 2.4.5, “Aggiornamento del installazione del Geocoder Tiger” for the non-extension model upgrade.

  2. Connect to your database with psql or pgAdmin and run the following command:

    CREATE EXTENSION postgis_tiger_geocoder FROM unpackaged;

2.4.2. Tiger Geocoder Enabling your PostGIS database: Not Using Extensions

Anzitutto installate PostGIS utilizzando le istruzioni riportate sopra.

If you don't have an extras folder, download http://postgis.net/stuff/postgis-3.2.0dev.tar.gz

tar xvfz postgis-3.2.0dev.tar.gz

cd postgis-3.2.0dev/extras/tiger_geocoder

Edit the tiger_loader_2015.sql (or latest loader file you find, unless you want to load different year) to the paths of your executables server etc or alternatively you can update the loader_platform table once installed. If you don't edit this file or the loader_platform table, it will just contain common case locations of items and you'll have to edit the generated script after the fact when you run the Loader_Generate_Nation_Script and Loader_Generate_Script SQL functions.

If you are installing Tiger geocoder for the first time edit either the create_geocode.bat script If you are on windows or the create_geocode.sh if you are on Linux/Unix/Mac OSX with your PostgreSQL specific settings and run the corresponding script from the commandline.

Verify that you now have a tiger schema in your database and that it is part of your database search_path. If it is not, add it with a command something along the line of:

ALTER DATABASE geocoder SET search_path=public, tiger;

The normalizing address functionality works more or less without any data except for tricky addresses. Run this test and verify things look like this:

SELECT pprint_addy(normalize_address('202 East Fremont Street, Las Vegas, Nevada 89101')) As pretty_address;
pretty_address
---------------------------------------
202 E Fremont St, Las Vegas, NV 89101
                        

2.4.3. Using Address Standardizer Extension with Tiger geocoder

One of the many complaints of folks is the address normalizer function Normalize_Address function that normalizes an address for prepping before geocoding. The normalizer is far from perfect and trying to patch its imperfectness takes a vast amount of resources. As such we have integrated with another project that has a much better address standardizer engine. To use this new address_standardizer, you compile the extension as described in Section 2.3, “Installing and Using the address standardizer” and install as an extension in your database.

Once you install this extension in the same database as you have installed postgis_tiger_geocoder, then the Pagc_Normalize_Address can be used instead of Normalize_Address. This extension is tiger agnostic, so can be used with other data sources such as international addresses. The tiger geocoder extension does come packaged with its own custom versions of rules table ( tiger.pagc_rules) , gaz table (tiger.pagc_gaz), and lex table (tiger.pagc_lex). These you can add and update to improve your standardizing experience for your own needs.

2.4.4. Caricamento dei dati Tiger

Le istruzioni dettagliate per il caricamento dei dati sono disponibili nel file extras/tiger_geocoder/tiger_2011/README. Di seguito si illustrano i passaggi generali.

Il processo di caricamento scarica i dati per ciascuno stato richiesto dal sito del censimento, estrare i file, e li carica nelle rispettive tabelle. La tabella di ogni stato eredita le proprietà dalle tabelle definite nello schema tiger, per cui è sufficiente eseguire le interrogazioni su queste tabelle per accedere a tutti i dati. E' altresì possibile cancellare le tabelle per un dato stato tramite lo script Drop_State_Tables_Generate_Script, qualora aveste necessità di ricaricare uno stato o se questo non vi serve più.

Per caricare i dati avrete bisogno dei seguenti strumenti:

  • Uno strumento per decomprimere i file zip dal sito web dei censimenti.

    Per sistemi tipo Unix: l'eseguibile unzip è di soiito già installato.

    Per Windows, 7-zip è uno strumento libero di compressione/decompressione, che può essere scaricato dal sito http://www.7-zip.org/

  • Il programam da riga di comando shp2pgsql, che viene installato di base quando nistallate PostGIS.

  • wget è uno strumento per la copia di file da web, solitamente installato nella maggior parte dei sistemi Unix/Linux.

    Se siete su Windows, potete reperire i file binari precompilati da http://gnuwin32.sourceforge.net/packages/wget.htm

If you are upgrading from tiger_2010, you'll need to first generate and run Drop_Nation_Tables_Generate_Script. Before you load any state data, you need to load the nation wide data which you do with Loader_Generate_Nation_Script. Which will generate a loader script for you. Loader_Generate_Nation_Script is a one-time step that should be done for upgrading (from 2010) and for new installs.

To load state data refer to Loader_Generate_Script to generate a data load script for your platform for the states you desire. Note that you can install these piecemeal. You don't have to load all the states you want all at once. You can load them as you need them.

Dopo aver caricato i dati per gli stati cui siete interessati, assicuratevi di eseguire:

SELECT install_missing_indexes();

come descritto in Install_Missing_Indexes.

Per vedere se le cose funzionano come dovrebbero, provate a eseguire la geocodifica di un indirizzo nel vostro stato utilizzando Geocode

2.4.5. Aggiornamento del installazione del Geocoder Tiger

If you have Tiger Geocoder packaged with 2.0+ already installed, you can upgrade the functions at any time even from an interim tar ball if there are fixes you badly need. This will only work for Tiger geocoder not installed with extensions.

If you don't have an extras folder, download http://postgis.net/stuff/postgis-3.2.0dev.tar.gz

tar xvfz postgis-3.2.0dev.tar.gz

cd postgis-3.2.0dev/extras/tiger_geocoder/tiger_2011

Locate the upgrade_geocoder.bat script If you are on windows or the upgrade_geocoder.sh if you are on Linux/Unix/Mac OSX. Edit the file to have your postgis database credentials.

If you are upgrading from 2010 or 2011, make sure to unremark out the loader script line so you get the latest script for loading 2012 data.

Then run th corresponding script from the commandline.

Poi cancellate tutte le tabelle delle nazioni e caricate quelle nuove. Potete generare uno script per la cancellazione con il codice SQL illustrato in Drop_Nation_Tables_Generate_Script

SELECT drop_nation_tables_generate_script();

Eseguite i comandi SQL DROP che vengono generati.

Generate uno script per il caricamento di uno stato con l'istruzione SELECT come illustrato in Loader_Generate_Nation_Script

Per Windows

SELECT loader_generate_nation_script('windows'); 

Per unix/linux

SELECT loader_generate_nation_script('sh');

Fate riferimento a Section 2.4.4, “Caricamento dei dati Tiger” per istruzioni su come eseguire lo script generato. Questo passaggio deve essere eseguito solo una volta.

[Note]

Potete avere una combinazione di tabelle degli stati sia per il 2010 che per il 2011 e potete aggiornare ogni stato separatamente. Prima di aggiornare uno stato al 2011, dovete prima eliminare la corrispondente tabella 2012 utilizzando Drop_State_Tables_Generate_Script.

2.5. Common Problems during installation

Quando l'installazione o l'aggiornamento non vanno come previsto, diverse cose vanno controllate.

  1. Controllate di aver installato PostgreSQL 9.6 o più recente, e che state compilando con il sorgente PostgreSQL nella versione corrispondente alla versione di PostgreSQL che sta girando. Si possono verificare casi di confusione quando la vostra distribuzione (Linux) ha PostgreSQL già installao, o quando avete installato PostgreSQL in precedenza e ve ne siete dimenticati. PostGIS funzionerà solo con PostgreSQL 9.6 o più recente, e si potrebbero ricevere messaggi di errore strani o inattesi se utilizzate una versione più vecchia. Per verificare quale versione di PostgreSQL sta girando, collegatevi al database utilizzando psql ed eseguite la seguente query:

    SELECT version();

    Se state utilizzando una distribuzione basata su RPM, potete verificare la presenza di pacchetti preinstallati utilizzando il comando rpm con la seguente sintassi: rpm -qa | grep postgresql

  2. Se l'aggiornamento non funziona, assicuratevi di eseguire il ripristino in un database che abbia già PostGIS installato.

    SELECT postgis_full_version();

Inoltre, verificate che configure abbia correttamente individuato il percorso e la versione di PostgreSQL, della libreria Proj4 e della libreria GEOS.

  1. L'uscita da configure viene utilizzata per generare il file postgis_config.h. Controllate che le variabili POSTGIS_PGSQL_VERSION, POSTGIS_PROJ_VERSION e POSTGIS_GEOS_VERSION siano assegnate correttamente.

Chapter 3. PostGIS Administration

3.1. Performance Tuning

Tuning for PostGIS performance is much like tuning for any PostgreSQL workload. The only additional consideration is that geometries and rasters are usually large, so memory-related optimizations generally have more of an impact on PostGIS than other types of PostgreSQL queries.

For general details about optimizing PostgreSQL, refer to Tuning your PostgreSQL Server.

For PostgreSQL 9.4+ configuration can be set at the server level without touching postgresql.conf or postgresql.auto.conf by using the ALTER SYSTEM command.

ALTER SYSTEM SET work_mem = '256MB';
-- this forces non-startup configs to take effect for new connections
SELECT pg_reload_conf();
-- show current setting value
-- use SHOW ALL to see all settings
SHOW work_mem;

In addition to the Postgres settings, PostGIS has some custom settings which are listed in Section 8.23, “Grand Unified Custom Variables (GUCs)”.

3.1.1. Startup

These settings are configured in postgresql.conf:

constraint_exclusion

  • Default: partition

  • This is generally used for table partitioning. The default for this is set to "partition" which is ideal for PostgreSQL 8.4 and above since it will force the planner to only analyze tables for constraint consideration if they are in an inherited hierarchy and not pay the planner penalty otherwise.

shared_buffers

  • Default: ~128MB in PostgreSQL 9.6

  • Set to about 25% to 40% of available RAM. On windows you may not be able to set as high.

max_worker_processes This setting is only available for PostgreSQL 9.4+. For PostgreSQL 9.6+ this setting has additional importance in that it controls the max number of processes you can have for parallel queries.

  • Default: 8

  • Sets the maximum number of background processes that the system can support. This parameter can only be set at server start.

3.1.2. Runtime

work_mem - sets the size of memory used for sort operations and complex queries

  • Default: 1-4MB

  • Adjust up for large dbs, complex queries, lots of RAM

  • Adjust down for many concurrent users or low RAM.

  • If you have lots of RAM and few developers:

    SET work_mem TO '256MB';

maintenance_work_mem - the memory size used for VACUUM, CREATE INDEX, etc.

  • Default: 16-64MB

  • Generally too low - ties up I/O, locks objects while swapping memory

  • Recommend 32MB to 1GB on production servers w/lots of RAM, but depends on the # of concurrent users. If you have lots of RAM and few developers:

    SET maintenance_work_mem TO '1GB';

max_parallel_workers_per_gather

This setting is only available for PostgreSQL 9.6+ and will only affect PostGIS 2.3+, since only PostGIS 2.3+ supports parallel queries. If set to higher than 0, then some queries such as those involving relation functions like ST_Intersects can use multiple processes and can run more than twice as fast when doing so. If you have a lot of processors to spare, you should change the value of this to as many processors as you have. Also make sure to bump up max_worker_processes to at least as high as this number.

  • Default: 0

  • Sets the maximum number of workers that can be started by a single Gather node. Parallel workers are taken from the pool of processes established by max_worker_processes. Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may be inefficient. Setting this value to 0, which is the default, disables parallel query execution.

3.2. Configuring raster support

If you enabled raster support you may want to read below how to properly configure it.

As of PostGIS 2.1.3, out-of-db rasters and all raster drivers are disabled by default. In order to re-enable these, you need to set the following environment variables POSTGIS_GDAL_ENABLED_DRIVERS and POSTGIS_ENABLE_OUTDB_RASTERS in the server environment. For PostGIS 2.2, you can use the more cross-platform approach of setting the corresponding Section 8.23, “Grand Unified Custom Variables (GUCs)”.

If you want to enable offline raster:

POSTGIS_ENABLE_OUTDB_RASTERS=1

Any other setting or no setting at all will disable out of db rasters.

In order to enable all GDAL drivers available in your GDAL install, set this environment variable as follows

POSTGIS_GDAL_ENABLED_DRIVERS=ENABLE_ALL

If you want to only enable specific drivers, set your environment variable as follows:

POSTGIS_GDAL_ENABLED_DRIVERS="GTiff PNG JPEG GIF XYZ"
[Note]

If you are on windows, do not quote the driver list

Setting environment variables varies depending on OS. For PostgreSQL installed on Ubuntu or Debian via apt-postgresql, the preferred way is to edit /etc/postgresql/10/main/environment where 10 refers to version of PostgreSQL and main refers to the cluster.

On windows, if you are running as a service, you can set via System variables which for Windows 7 you can get to by right-clicking on Computer->Properties Advanced System Settings or in explorer navigating to Control Panel\All Control Panel Items\System. Then clicking Advanced System Settings ->Advanced->Environment Variables and adding new system variables.

After you set the environment variables, you'll need to restart your PostgreSQL service for the changes to take effect.

3.3. Creating spatial databases

3.3.1. Spatially enable database using EXTENSION

If you are using PostgreSQL 9.1+ and have compiled and installed the extensions/postgis modules, you can turn a database into a spatial one using the EXTENSION mechanism.

Core postgis extension includes geometry, geography, spatial_ref_sys and all the functions and comments. Raster and topology are packaged as a separate extension.

Run the following SQL snippet in the database you want to enable spatially:

CREATE EXTENSION IF NOT EXISTS plpgsql;
      CREATE EXTENSION postgis;
      CREATE EXTENSION postgis_raster; -- OPTIONAL
      CREATE EXTENSION postgis_topology; -- OPTIONAL

3.3.2. Spatially enable database without using EXTENSION (discouraged)

[Note]

This is generally only needed if you cannot or don't want to get PostGIS installed in the PostgreSQL extension directory (for example during testing, development or in a restricted environment).

Adding PostGIS objects and function definitions into your database is done by loading the various sql files located in [prefix]/share/contrib as specified during the build phase.

The core PostGIS objects (geometry and geography types, and their support functions) are in the postgis.sql script. Raster objects are in the rtpostgis.sql script. Topology objects are in the topology.sql script.

For a complete set of EPSG coordinate system definition identifiers, you can also load the spatial_ref_sys.sql definitions file and populate the spatial_ref_sys table. This will permit you to perform ST_Transform() operations on geometries.

If you wish to add comments to the PostGIS functions, you can find them in the postgis_comments.sql script. Comments can be viewed by simply typing \dd [function_name] from a psql terminal window.

Run the following Shell commands in your terminal:

DB=[yourdatabase]
    SCRIPTSDIR=`pg_config --sharedir`/contrib/postgis-3.1/

    # Core objects
    psql -d ${DB} -f ${SCRIPTSDIR}/postgis.sql
    psql -d ${DB} -f ${SCRIPTSDIR}/spatial_ref_sys.sql
    psql -d ${DB} -f ${SCRIPTSDIR}/postgis_comments.sql # OPTIONAL

    # Raster support (OPTIONAL)
    psql -d ${DB} -f ${SCRIPTSDIR}/rtpostgis.sql
    psql -d ${DB} -f ${SCRIPTSDIR}/raster_comments.sql # OPTIONAL

    # Topology support (OPTIONAL)
    psql -d ${DB} -f ${SCRIPTSDIR}/topology.sql
    psql -d ${DB} -f ${SCRIPTSDIR}/topology_comments.sql # OPTIONAL

3.3.3. Create a spatially-enabled database from a template

Some packaged distributions of PostGIS (in particular the Win32 installers for PostGIS >= 1.1.5) load the PostGIS functions into a template database called template_postgis. If the template_postgis database exists in your PostgreSQL installation then it is possible for users and/or applications to create spatially-enabled databases using a single command. Note that in both cases, the database user must have been granted the privilege to create new databases.

From the shell:

# createdb -T template_postgis my_spatial_db

From SQL:

postgres=# CREATE DATABASE my_spatial_db TEMPLATE=template_postgis

3.4. Upgrading spatial databases

Upgrading existing spatial databases can be tricky as it requires replacement or introduction of new PostGIS object definitions.

Unfortunately not all definitions can be easily replaced in a live database, so sometimes your best bet is a dump/reload process.

PostGIS provides a SOFT UPGRADE procedure for minor or bugfix releases, and a HARD UPGRADE procedure for major releases.

Before attempting to upgrade PostGIS, it is always worth to backup your data. If you use the -Fc flag to pg_dump you will always be able to restore the dump with a HARD UPGRADE.

3.4.1. Soft upgrade

If you installed your database using extensions, you'll need to upgrade using the extension model as well. If you installed using the old sql script way, then you should upgrade using the sql script way. Please refer to the appropriate.

3.4.1.1. Soft Upgrade Pre 9.1+ or without extensions

This section applies only to those who installed PostGIS not using extensions. If you have extensions and try to upgrade with this approach you'll get messages like:

can't drop ... because postgis extension depends on it

NOTE: if you are moving from PostGIS 1.* to PostGIS 2.* or from PostGIS 2.* prior to r7409, you cannot use this procedure but would rather need to do a HARD UPGRADE.

After compiling and installing (make install) you should find a set of *_upgrade.sql files in the installation folders. You can list them all with:

ls `pg_config --sharedir`/contrib/postgis-3.2.0dev/*_upgrade.sql

Load them all in turn, starting from postgis_upgrade.sql.

psql -f postgis_upgrade.sql -d your_spatial_database

The same procedure applies to raster, topology and sfcgal extensions, with upgrade files named rtpostgis_upgrade.sql, topology_upgrade.sql and sfcgal_upgrade.sql respectively. If you need them:

psql -f rtpostgis_upgrade.sql -d your_spatial_database
psql -f topology_upgrade.sql -d your_spatial_database
psql -f sfcgal_upgrade.sql -d your_spatial_database
[Note]

If you can't find the postgis_upgrade.sql specific for upgrading your version you are using a version too early for a soft upgrade and need to do a HARD UPGRADE.

The PostGIS_Full_Version function should inform you about the need to run this kind of upgrade using a "procs need upgrade" message.

3.4.1.2. Soft Upgrade 9.1+ using extensions

If you originally installed PostGIS with extensions, then you need to upgrade using extensions as well. Doing a minor upgrade with extensions, is fairly painless.

ALTER EXTENSION postgis UPDATE TO "3.2.0dev";
ALTER EXTENSION postgis_topology UPDATE TO "3.2.0dev";

If you get an error notice something like:

No migration path defined for ... to 3.2.0dev

Then you'll need to backup your database, create a fresh one as described in Section 3.3.1, “Spatially enable database using EXTENSION” and then restore your backup ontop of this new database.

If you get a notice message like:

Version "3.2.0dev" of extension "postgis" is already installed

Then everything is already up to date and you can safely ignore it. UNLESS you're attempting to upgrade from an development version to the next (which doesn't get a new version number); in that case you can append "next" to the version string, and next time you'll need to drop the "next" suffix again:

ALTER EXTENSION postgis UPDATE TO "3.2.0devnext";
ALTER EXTENSION postgis_topology UPDATE TO "3.2.0devnext";
[Note]

If you installed PostGIS originally without a version specified, you can often skip the reinstallation of postgis extension before restoring since the backup just has CREATE EXTENSION postgis and thus picks up the newest latest version during restore.

[Note]

If you are upgrading PostGIS extension from a version prior to 3.0.0 you'll end up with an unpackaged PostGIS Raster support. You can repackage the raster support using:

    CREATE EXTENSION postgis_raster FROM unpackaged;
    

And then, if you don't need it, drop it with:

DROP EXTENSION postgis_raster;
    

3.4.2. Hard upgrade

By HARD UPGRADE we mean full dump/reload of postgis-enabled databases. You need a HARD UPGRADE when PostGIS objects' internal storage changes or when SOFT UPGRADE is not possible. The Release Notes appendix reports for each version whether you need a dump/reload (HARD UPGRADE) to upgrade.

The dump/reload process is assisted by the postgis_restore.pl script which takes care of skipping from the dump all definitions which belong to PostGIS (including old ones), allowing you to restore your schemas and data into a database with PostGIS installed without getting duplicate symbol errors or bringing forward deprecated objects.

Supplementary instructions for windows users are available at Windows Hard upgrade.

The Procedure is as follows:

  1. Create a "custom-format" dump of the database you want to upgrade (let's call it olddb) include binary blobs (-b) and verbose (-v) output. The user can be the owner of the db, need not be postgres super account.

    pg_dump -h localhost -p 5432 -U postgres -Fc -b -v -f "/somepath/olddb.backup" olddb
  2. Do a fresh install of PostGIS in a new database -- we'll refer to this database as newdb. Please refer to Section 3.3.2, “Spatially enable database without using EXTENSION (discouraged)” and Section 3.3.1, “Spatially enable database using EXTENSION” for instructions on how to do this.

    The spatial_ref_sys entries found in your dump will be restored, but they will not override existing ones in spatial_ref_sys. This is to ensure that fixes in the official set will be properly propagated to restored databases. If for any reason you really want your own overrides of standard entries just don't load the spatial_ref_sys.sql file when creating the new db.

    If your database is really old or you know you've been using long deprecated functions in your views and functions, you might need to load legacy.sql for all your functions and views etc. to properly come back. Only do this if _really_ needed. Consider upgrading your views and functions before dumping instead, if possible. The deprecated functions can be later removed by loading uninstall_legacy.sql.

  3. Restore your backup into your fresh newdb database using postgis_restore.pl. Unexpected errors, if any, will be printed to the standard error stream by psql. Keep a log of those.

    perl utils/postgis_restore.pl "/somepath/olddb.backup" | psql -h localhost -p 5432 -U postgres newdb 2> errors.txt

Errors may arise in the following cases:

  1. Some of your views or functions make use of deprecated PostGIS objects. In order to fix this you may try loading legacy.sql script prior to restore or you'll have to restore to a version of PostGIS which still contains those objects and try a migration again after porting your code. If the legacy.sql way works for you, don't forget to fix your code to stop using deprecated functions and drop them loading uninstall_legacy.sql.

  2. Some custom records of spatial_ref_sys in dump file have an invalid SRID value. Valid SRID values are bigger than 0 and smaller than 999000. Values in the 999000.999999 range are reserved for internal use while values > 999999 can't be used at all. All your custom records with invalid SRIDs will be retained, with those > 999999 moved into the reserved range, but the spatial_ref_sys table would lose a check constraint guarding for that invariant to hold and possibly also its primary key ( when multiple invalid SRIDS get converted to the same reserved SRID value ).

    In order to fix this you should copy your custom SRS to a SRID with a valid value (maybe in the 910000..910999 range), convert all your tables to the new srid (see UpdateGeometrySRID), delete the invalid entry from spatial_ref_sys and re-construct the check(s) with:

    ALTER TABLE spatial_ref_sys ADD CONSTRAINT spatial_ref_sys_srid_check check (srid > 0 AND srid < 999000 );

    ALTER TABLE spatial_ref_sys ADD PRIMARY KEY(srid));

    If you are upgrading an old database containing french IGN cartography, you will have probably SRIDs out of range and you will see, when importing your database, issues like this :

     WARNING: SRID 310642222 converted to 999175 (in reserved zone)

    In this case, you can try following steps : first throw out completely the IGN from the sql which is resulting from postgis_restore.pl. So, after having run :

    perl utils/postgis_restore.pl "/somepath/olddb.backup" > olddb.sql

    run this command :

    grep -v IGNF olddb.sql > olddb-without-IGN.sql

    Create then your newdb, activate the required Postgis extensions, and insert properly the french system IGN with : this script After these operations, import your data :

    psql -h localhost -p 5432 -U postgres -d newdb -f olddb-without-IGN.sql  2> errors.txt

Chapter 4. Data Management

4.1. Spatial Data Model

4.1.1. OGC Geometry

The Open Geospatial Consortium (OGC) developed the Simple Features Access standard (SFA) to provide a model for geospatial data. It defines the fundamental spatial data type of Geometry, with a set of subtypes that represent various kinds and dimensions of geometric shapes. The latest SFA version Simple Features Access - Part 1: Common architecture v1.2.1 adds subtypes for the more complex geometric objects PolyhedralSurfaces, Triangles and TINs.

The geometry types model shapes on the 2-dimensional Cartesian plane constructed from points and line segments. The size and location of shapes are specified by their coordinates. The points and line segments are defined by one or two coordinates in the plane. Each coordinate has a X and Y value determining its location in the plane.

Coordinates may also contain optional Z and M ordinate values. The Z ordinate is usually used to represent elevation above the plane. The M ordinate can be used to contain a measure value, which may represent time or distance. If Z or M values are present in a geometry value, they must be defined for each point in the geometry. If a geometry has Z or M ordinates the coordinate dimension is 3D; if it has both Z and M the coordinate dimension is 4D.

Each geometry value is associated with a spatial reference system indicating the coordinate system in which it is embedded. See Section 4.5, “Spatial Reference Systems”. The spatial reference system is identifed by a SRID number. In planar reference systems the X and Y coordinates typically represent easting and northing, while in geodetic systems they represent longitude and latitude. The units of the X and Y axes are determined by the reference system. SRID 0 represents an infinite Cartesian plane with no units assigned to its axes.

The geometry dimension is a property of geometry types. Point types have dimension 0, linear types have dimension 1, and polygonal types have dimension 2. Collections have the dimension of the maximum element dimension.

A geometry value may be empty. Empty values contain no vertices (for atomic geometry types) or no elements (for collections).

The geometry model allows evaluating topological spatial relationships as described in Section 5.1.1, “Dimensionally Extended 9-Intersection Model”. To support this the concepts of interior, boundary and exterior are defined for each geometry type.

4.1.1.1. Point

A Point is a 0-dimensional geometry that represents a single location in coordinate space.

POINT (1 2)

4.1.1.2. LineString

A LineString is a 1-dimensional line formed by a contigous sequence of line segments. Each line segment is defined by two points, with the end point of one segment forming the start point of the next segment. A LineString must have at least two points. LineStrings may cross themselves (self-intersect). A LineString is closed if the start and end points are the same.

LINESTRING (1 2, 3 4)

4.1.1.3. LinearRing

A LinearRing is a LineString which is closed and simple (non-intersecting).

LINEARRING (0 0 0,4 0 0,4 4 0,0 4 0,0 0 0)

4.1.1.4. Polygon

A Polygon is a 2-dimensional planar region, delimited by an exterior boundary (the shell) and zero or more interior boundaries (holes). The boundaries are formed by LinearRings.

POLYGON ((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

4.1.1.5. MultiPoint

A MultiPoint is a collection of Points.

MULTIPOINT ( (0 0), (1 2) )

4.1.1.6. MultiLineString

A MultiLineString is a collection of LineStrings. A MultiLineString is closed if each of its element is closed.

MULTILINESTRING ( (0 0,1 1,1 2), (2 3,3 2,5 4) )

4.1.1.7. MultiPolygon

A MultiPolygon is a collection of non-overlapping, non-adjacent Polygons. Polygons in the collection may touch in only a finite number of points.

MULTIPOLYGON (((1 5, 5 5, 5 1, 1 1, 1 5)), ((6 5, 9 1, 6 1, 6 5)))

4.1.1.8. GeometryCollection

A GeometryCollection is a heterogenous (mixed) collection of geometries.

GEOMETRYCOLLECTION ( POINT(2 3), LINESTRING(2 3,3 4))

4.1.1.9. PolyhedralSurface

A PolyhedralSurface is a contiguous collection of patches or facets which share some edges. Each patch is a planar Polygon. If the Polygon coordinates have Z ordinates then the surface is 3-dimensional.

POLYHEDRALSURFACE (
  ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
  ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
  ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
  ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
  ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
  ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

4.1.1.10. Triangle

A Triangle is a polygon defined by 3 distinct non-collinear points.

TRIANGLE ((0 0, 0 9, 9 0, 0 0))

4.1.1.11. Tin

A Tin is a collection of non-overlapping Triangles representing a triangulated irregular network.

TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

4.1.2. SQL/MM Part 3 - Curves

The ISO/IEC 13249-3 SQL Multimedia - Spatial standard (SQL/MM) extends the OGC SFA to define Geometry subtypes containing curves with circular arcs. The SQL/MM types supprt 3DM, 3DZ and 4D coordinates.

[Note]

All floating point comparisons within the SQL-MM implementation are performed to a specified tolerance, currently 1E-8.

4.1.2.1. CircularString

CircularString is the basic curve type, similar to a LineString in the linear world. A single arc segment requires three points: the start and end points (first and third) and some other point on the arc. The exception to this is for a closed circle, where the start and end points are the same. In this case the second point MUST be the center of the arc, ie the opposite side of the circle. To chain arcs together, the last point of the previous arc is the first point of the next arc, just like in a LineString. This means that a valid circular string must have an odd number of points greater than 1.

CIRCULARSTRING(0 0, 1 1, 1 0)

CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0)

4.1.2.2. CompoundCurve

A CompoundCurve is a single continuous curve that may contain both circular arc segments and linear segments. That means that in addition to having well-formed components, the end point of every component (except the last) must be coincident with the start point of the following component.

COMPOUNDCURVE( CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))

4.1.2.3. CurvePolygon

A CurvePolygon is like a polygon, with an outer ring and zero or more inner rings. The difference is that a ring can be a CircularString or CompoundCurve as well as a LineString.

As of PostGIS 1.4 PostGIS supports compound curves in a curve polygon.

CURVEPOLYGON(
  CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),
  (1 1, 3 3, 3 1, 1 1) )

Example: A CurvePolygon with the shell defined by a CompoundCurve containing a CircularString and a LineString, and a hole defined by a CircularString

CURVEPOLYGON(
  COMPOUNDCURVE( CIRCULARSTRING(0 0,2 0, 2 1, 2 3, 4 3),
                 (4 3, 4 5, 1 4, 0 0)),
  CIRCULARSTRING(1.7 1, 1.4 0.4, 1.6 0.4, 1.6 0.5, 1.7 1) )

4.1.2.4. MultiCurve

A MultiCurve is a collection of curves which can include LineStrings, CircularStrings or CompoundCurves.

MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4))

4.1.2.5. MultiSurface

A MultiSurface is a collection of surfaces, which can be (linear) Polygons or CurvePolygons.

MULTISURFACE(
  CURVEPOLYGON(
    CIRCULARSTRING( 0 0, 4 0, 4 4, 0 4, 0 0),
    (1 1, 3 3, 3 1, 1 1)),
  ((10 10, 14 12, 11 10, 10 10), (11 11, 11.5 11, 11 11.5, 11 11)))

4.1.3. WKT and WKB

The OGC SFA specification defines two standard formats for representing geometry values for external use: Well-Known Text (WKT) and Well-Known Binary (WKB). Both WKT and WKB include information about the type of the object and the coordinates which define it.

Well-Known Text (WKT) provides a standard textual representation of spatial data. Examples of WKT representations of spatial objects are:

  • POINT(0 0)

  • POINT Z (0 0 0)

  • POINT ZM (0 0 0 0)

  • POINT EMPTY

  • LINESTRING(0 0,1 1,1 2)

  • LINESTRING EMPTY

  • POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))

  • MULTIPOINT((0 0),(1 2))

  • MULTIPOINT Z ((0 0 0),(1 2 3))

  • MULTIPOINT EMPTY

  • MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4))

  • MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

  • GEOMETRYCOLLECTION(POINT(2 3),LINESTRING(2 3,3 4))

  • GEOMETRYCOLLECTION EMPTY

Input and output of WKT is provided by the functions ST_AsText and ST_GeomFromText:

text WKT = ST_AsText(geometry);
geometry = ST_GeomFromText(text WKT, SRID);

For example, a statement to create and insert a spatial object from WKT and a SRID is:

INSERT INTO geotable ( geom, name )
  VALUES ( ST_GeomFromText('POINT(-126.4 45.32)', 312), 'A Place');

Well-Known Binary (WKB) provides a portable, faithful representation of spatial data as binary data (arrays of bytes). Examples of the WKB representations of spatial objects are:

  • WKT: POINT(1 1)

    WKB: 0101000000000000000000F03F000000000000F03

  • WKT: LINESTRING (2 2, 9 9)

    WKB: 0102000000020000000000000000000040000000000000004000000000000022400000000000002240

Input and output of WKB is provided by the functions ST_AsBinary and ST_GeomFromWKB:

bytea WKB = ST_AsBinary(geometry);
geometry = ST_GeomFromWKB(bytea WKB, SRID);

For example, a statement to create and insert a spatial object from WKB is:

INSERT INTO geotable ( geom, name )
  VALUES ( ST_GeomFromWKB('\x0101000000000000000000f03f000000000000f03f', 312), 'A Place');

4.2. Geometry Data Type

PostGIS implements the OGC Simple Features model by defining a PostgreSQL data type called geometry. It represents all of the geometry subtypes by using an internal type code (see GeometryType and ST_GeometryType). This allows modelling spatial features as rows of tables defined with a column of type geometry.

The geometry data type is opaque, which means that all access is done via invoking functions on geometry values. Functions allow creating geometry objects, accessing or updating all internal fields, and compute new geometry values. PostGIS supports all the functions specified in the OGC Simple feature access - Part 2: SQL option (SFS) specification, as well many others. See Chapter 8, Guida a PostGIS for the full list of functions.

[Note]

PostGIS follows the SFA standard by prefixing spatial functions with "ST_". This was intended to stand for "Spatial and Temporal", but the temporal part of the standard was never developed. Instead it can be interpreted as "Spatial Type".

The SFA standard specifies that spatial objects include a Spatial Reference System identifier (SRID). The SRID is required when creating spatial objects for insertion into the database (it may be defaulted to 0). See ST_SRID and Section 4.5, “Spatial Reference Systems”

To make querying geometry efficient PostGIS defines various kinds of spatial indexes, and spatial operators to use them. See Section 4.9, “Building Spatial Indexes” and Section 5.2, “Using Spatial Indexes” for details.

4.2.1. PostGIS EWKB and EWKT

OGC SFA specifications initially supported only 2D geometries, and the geometry SRID is not included in the input/output representations. The OGC SFA specification 1.2.1 (which aligns with the ISO 19125 standard) adds support for 3D (ZYZ and XYM) and 4D (XYZM) coordinates, but still does not include the SRID value.

Because of these limitations PostGIS defined extended EWKB and EWKT formats. They provide 3D (XYZ and XYM) and 4D (XYZM) coordinate support and include SRID information. Including all geometry information allows PostGIS to use EWKB as the format of record (e.g. in DUMP files).

EWKB and EWKT are used for the "canonical forms" of PostGIS data objects. For input, the canonical form for binary data is EWKB, and for text data either EWKB or EWKT is accepted. This allows geometry values to be created by casting a text value in either HEXEWKB or EWKT to a geometry value using ::geometry. For output, the canonical form for binary is EWKB, and for text it is HEXEWKB (hex-encoded EWKB).

For example this statement creates a geometry by casting from an EWKT text value, and outputs it using the canonical form of HEXEWKB:

SELECT 'SRID=4;POINT(0 0)'::geometry;
  geometry
  ----------------------------------------------------
  01010000200400000000000000000000000000000000000000

PostGIS EWKT output has a few differences to OGC WKT:

  • For 3DZ geometries the Z qualifier is omitted:

    OGC: POINT Z (1 2 3)

    EWKT: POINT (1 2 3)

  • For 3DM geometries the M qualifier is included:

    OGC: POINT M (1 2 3)

    EWKT: POINTM (1 2 3)

  • For 4D geometries the ZM qualifier is omitted:

    OGC: POINT ZM (1 2 3 4)

    EWKT: POINT (1 2 3 4)

EWKT avoids over-specifying dimensionality and the inconsistencies that can occur with the OGC/ISO format, such as:

  • POINT ZM (1 1)

  • POINT ZM (1 1 1)

  • POINT (1 1 1 1)

[Caution]

PostGIS extended formats are currently a superset of the OGC ones, so that every valid OGC WKB/WKT is also valid EWKB/EWKT. However, this might vary in the future, if the OGC extends a format in a way that conflicts with the PosGIS definition. Thus you SHOULD NOT rely on this compatibility!

Examples of the EWKT text representation of spatial objects are:

  • POINT(0 0 0) -- XYZ

  • SRID=32632;POINT(0 0) -- XY with SRID

  • POINTM(0 0 0) -- XYM

  • POINT(0 0 0 0) -- XYZM

  • SRID=4326;MULTIPOINTM(0 0 0,1 2 1) -- XYM with SRID

  • MULTILINESTRING((0 0 0,1 1 0,1 2 1),(2 3 1,3 2 1,5 4 1))

  • POLYGON((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

  • MULTIPOLYGON(((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)),((-1 -1 0,-1 -2 0,-2 -2 0,-2 -1 0,-1 -1 0)))

  • GEOMETRYCOLLECTIONM( POINTM(2 3 9), LINESTRINGM(2 3 4, 3 4 5) )

  • MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4) )

  • POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

  • TRIANGLE ((0 0, 0 9, 9 0, 0 0))

  • TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

Input and output using these formats is available using the following functions:

bytea EWKB = ST_AsEWKB(geometry);
text EWKT = ST_AsEWKT(geometry);
geometry = ST_GeomFromEWKB(bytea EWKB);
geometry = ST_GeomFromEWKT(text EWKT);

For example, a statement to create and insert a PostGIS spatial object using EWKT is:

INSERT INTO geotable ( geom, name )
  VALUES ( ST_GeomFromEWKT('SRID=312;POINTM(-126.4 45.32 15)'), 'A Place' )

4.3. Geography Data Type

The PostGIS geography data type provides native support for spatial features represented on "geographic" coordinates (sometimes called "geodetic" coordinates, or "lat/lon", or "lon/lat"). Geographic coordinates are spherical coordinates expressed in angular units (degrees).

The basis for the PostGIS geometry data type is a plane. The shortest path between two points on the plane is a straight line. That means calculations on geometries (areas, distances, lengths, intersections, etc) can be calculated using cartesian mathematics and straight line vectors.

The basis for the PostGIS geographic data type is a sphere. The shortest path between two points on the sphere is a great circle arc. That means that calculations on geographies (areas, distances, lengths, intersections, etc) must be calculated on the sphere, using more complicated mathematics. For more accurate measurements, the calculations must take the actual spheroidal shape of the world into account.

Because the underlying mathematics is much more complicated, there are fewer functions defined for the geography type than for the geometry type. Over time, as new algorithms are added, the capabilities of the geography type will expand.

It uses a data type called geography. None of the GEOS functions support the geography type. As a workaround one can convert back and forth between geometry and geography types.

Prior to PostGIS 2.2, the geography type only supported WGS 84 long lat (SRID:4326). For PostGIS 2.2 and above, any long/lat based spatial reference system defined in the spatial_ref_sys table can be used. You can even add your own custom spheroidal spatial reference system as described in geography type is not limited to earth.

Regardless which spatial reference system you use, the units returned by the measurement (ST_Distance, ST_Length, ST_Perimeter, ST_Area) and for input of ST_DWithin are in meters.

The geography type uses the PostgreSQL typmod definition format so that a table with a geography field can be added in a single step. All the standard OGC formats except for curves are supported.

4.3.1. Geography Basics

The geography type does not support curves, TINS, or POLYHEDRALSURFACEs, but other geometry types are supported. Standard geometry type data will autocast to geography if it is of SRID 4326. You can also use the EWKT and EWKB conventions to insert data.

  • POINT: Creating a table with 2D point geography when srid is not specified defaults to 4326 WGS 84 long lat:

    CREATE TABLE ptgeogwgs(gid serial PRIMARY KEY, geog geography(POINT) );

    POINT: Creating a table with 2D point geography in NAD83 longlat:

    CREATE TABLE ptgeognad83(gid serial PRIMARY KEY, geog geography(POINT,4269) );

    Creating a table with z coordinate point and explicitly specifying srid

    CREATE TABLE ptzgeogwgs84(gid serial PRIMARY KEY, geog geography(POINTZ,4326) );
  • LINESTRING

    CREATE TABLE lgeog(gid serial PRIMARY KEY, geog geography(LINESTRING) );
  • POLYGON

    --polygon NAD 1927 long lat
    CREATE TABLE lgeognad27(gid serial PRIMARY KEY, geog geography(POLYGON,4267) );
  • MULTIPOINT

  • MULTILINESTRING

  • MULTIPOLYGON

  • GEOMETRYCOLLECTION

The geography fields get registered in the geography_columns system view.

Now, check the "geography_columns" view and see that your table is listed.

You can create a new table with a GEOGRAPHY column using the CREATE TABLE syntax.

CREATE TABLE global_points (
    id SERIAL PRIMARY KEY,
    name VARCHAR(64),
    location GEOGRAPHY(POINT,4326)
  );

Note that the location column has type GEOGRAPHY and that geography type supports two optional modifiers: a type modifier that restricts the kind of shapes and dimensions allowed in the column; an SRID modifier that restricts the coordinate reference identifier to a particular number.

Allowable values for the type modifier are: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON. The modifier also supports dimensionality restrictions through suffixes: Z, M and ZM. So, for example a modifier of 'LINESTRINGM' would only allow line strings with three dimensions in, and would treat the third dimension as a measure. Similarly, 'POINTZM' would expect four dimensional data.

If you do not specify an SRID, the SRID will default to 4326 WGS 84 long/lat will be used, and all calculations will proceed using WGS84.

Once you have created your table, you can see it in the GEOGRAPHY_COLUMNS table:

-- See the contents of the metadata view
SELECT * FROM geography_columns;

You can insert data into the table the same as you would if it was using a GEOMETRY column:

-- Add some data into the test table
INSERT INTO global_points (name, location) VALUES ('Town', 'SRID=4326;POINT(-110 30)');
INSERT INTO global_points (name, location) VALUES ('Forest', 'SRID=4326;POINT(-109 29)');
INSERT INTO global_points (name, location) VALUES ('London', 'SRID=4326;POINT(0 49)');

Creating an index works the same as GEOMETRY. PostGIS will note that the column type is GEOGRAPHY and create an appropriate sphere-based index instead of the usual planar index used for GEOMETRY.

-- Index the test table with a spherical index
  CREATE INDEX global_points_gix ON global_points USING GIST ( location );

Query and measurement functions use units of meters. So distance parameters should be expressed in meters, and return values should be expected in meters (or square meters for areas).

-- Show a distance query and note, London is outside the 1000km tolerance
  SELECT name FROM global_points WHERE ST_DWithin(location, 'SRID=4326;POINT(-110 29)'::geography, 1000000);

You can see the power of GEOGRAPHY in action by calculating how close a plane flying from Seattle to London (LINESTRING(-122.33 47.606, 0.0 51.5)) comes to Reykjavik (POINT(-21.96 64.15)).

-- Distance calculation using GEOGRAPHY (122.2km)
  SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geography, 'POINT(-21.96 64.15)'::geography);

-- Distance calculation using GEOMETRY (13.3 "degrees")
  SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geometry, 'POINT(-21.96 64.15)'::geometry);

Testing different lon/lat projects. Any long lat spatial reference system listed in spatial_ref_sys table is allowed.

-- NAD 83 lon/lat
SELECT 'SRID=4269;POINT(-123 34)'::geography;
                    geography
----------------------------------------------------
 0101000020AD1000000000000000C05EC00000000000004140
(1 row)

-- NAD27 lon/lat
SELECT 'SRID=4267;POINT(-123 34)'::geography;

                    geography
----------------------------------------------------
 0101000020AB1000000000000000C05EC00000000000004140
(1 row)

-- NAD83 UTM zone meters, yields error since its a meter based projection
SELECT 'SRID=26910;POINT(-123 34)'::geography;

ERROR:  Only lon/lat coordinate systems are supported in geography.
LINE 1: SELECT 'SRID=26910;POINT(-123 34)'::geography;

The GEOGRAPHY type calculates the true shortest distance over the sphere between Reykjavik and the great circle flight path between Seattle and London.

Great Circle mapper The GEOMETRY type calculates a meaningless cartesian distance between Reykjavik and the straight line path from Seattle to London plotted on a flat map of the world. The nominal units of the result might be called "degrees", but the result doesn't correspond to any true angular difference between the points, so even calling them "degrees" is inaccurate.

4.3.2. When to use the Geography data type

The geography data type allows you to store data in longitude/latitude coordinates, but at a cost: there are fewer functions defined on GEOGRAPHY than there are on GEOMETRY; those functions that are defined take more CPU time to execute.

The data type you choose should be determined by the expected working area of the application you are building. Will your data span the globe or a large continental area, or is it local to a state, county or municipality?

  • If your data is contained in a small area, you might find that choosing an appropriate projection and using GEOMETRY is the best solution, in terms of performance and functionality available.

  • If your data is global or covers a continental region, you may find that GEOGRAPHY allows you to build a system without having to worry about projection details. You store your data in longitude/latitude, and use the functions that have been defined on GEOGRAPHY.

  • If you don't understand projections, and you don't want to learn about them, and you're prepared to accept the limitations in functionality available in GEOGRAPHY, then it might be easier for you to use GEOGRAPHY than GEOMETRY. Simply load your data up as longitude/latitude and go from there.

Refer to Section 15.11, “PostGIS Function Support Matrix” for compare between what is supported for Geography vs. Geometry. For a brief listing and description of Geography functions, refer to Section 15.4, “PostGIS Geography Support Functions”

4.3.3. Geography Advanced FAQ

4.3.3.1. Do you calculate on the sphere or the spheroid?
4.3.3.2. What about the date-line and the poles?
4.3.3.3. What is the longest arc you can process?
4.3.3.4. Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

4.3.3.1.

Do you calculate on the sphere or the spheroid?

By default, all distance and area calculations are done on the spheroid. You should find that the results of calculations in local areas match up will with local planar results in good local projections. Over larger areas, the spheroidal calculations will be more accurate than any calculation done on a projected plane.

All the geography functions have the option of using a sphere calculation, by setting a final boolean parameter to 'FALSE'. This will somewhat speed up calculations, particularly for cases where the geometries are very simple.

4.3.3.2.

What about the date-line and the poles?

All the calculations have no conception of date-line or poles, the coordinates are spherical (longitude/latitude) so a shape that crosses the dateline is, from a calculation point of view, no different from any other shape.

4.3.3.3.

What is the longest arc you can process?

We use great circle arcs as the "interpolation line" between two points. That means any two points are actually joined up two ways, depending on which direction you travel along the great circle. All our code assumes that the points are joined by the *shorter* of the two paths along the great circle. As a consequence, shapes that have arcs of more than 180 degrees will not be correctly modelled.

4.3.3.4.

Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

Because the polygon is so darned huge! Big areas are bad for two reasons: their bounds are huge, so the index tends to pull the feature no matter what query you run; the number of vertices is huge, and tests (distance, containment) have to traverse the vertex list at least once and sometimes N times (with N being the number of vertices in the other candidate feature).

As with GEOMETRY, we recommend that when you have very large polygons, but are doing queries in small areas, you "denormalize" your geometric data into smaller chunks so that the index can effectively subquery parts of the object and so queries don't have to pull out the whole object every time. Please consult ST_Subdivide function documentation. Just because you *can* store all of Europe in one polygon doesn't mean you *should*.

4.4. Spatial Tables

4.4.1. Creating a Spatial Table

Creating a table with spatial data, can be done in one step. As shown in the following example which creates a roads table with a 2D linestring geometry column in WGS84 long lat

CREATE TABLE ROADS (ID serial, ROAD_NAME text, geom geometry(LINESTRING,4326) );

We can add additional columns using standard ALTER TABLE command as we do in this next example where we add a 3-D linestring.

ALTER TABLE roads ADD COLUMN geom2 geometry(LINESTRINGZ,4326);

4.4.2. GEOMETRY_COLUMNS View

The OpenGIS "Simple Features Specification for SQL" defines the GEOMETRY_COLUMNS metadata table to describe geometry table structure. In order to ensure that metadata remains consistent, operations such as creating and removing a spatial column are carried out through special procedures defined by OpenGIS.

In PostGIS geometry_columns is a view reading from database system catalog tables. Its structure is:

\d geometry_columns
View "public.geometry_columns"
      Column       |          Type          | Modifiers
-------------------+------------------------+-----------
 f_table_catalog   | character varying(256) |
 f_table_schema    | character varying(256) |
 f_table_name      | character varying(256) |
 f_geometry_column | character varying(256) |
 coord_dimension   | integer                |
 srid              | integer                |
 type              | character varying(30)  |

The columns are:

f_table_catalog, f_table_schema, f_table_name

The fully qualified name of the feature table containing the geometry column. Note that the terms "catalog" and "schema" are Oracle-ish. There is no PostgreSQL analogue of "catalog" so that column is left blank . For "schema" the PostgreSQL schema name is used (public is the default).

f_geometry_column

The name of the geometry column in the feature table.

coord_dimension

The spatial dimension (2, 3 or 4 dimensional) of the column.

srid

The ID of the spatial reference system used for the coordinate geometry in this table. It is a foreign key reference to the spatial_ref_sys table (see Section 4.5.1, “SPATIAL_REF_SYS Table”).

type

The type of the spatial object. To restrict the spatial column to a single type, use one of: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION or corresponding XYM versions POINTM, LINESTRINGM, POLYGONM, MULTIPOINTM, MULTILINESTRINGM, MULTIPOLYGONM, GEOMETRYCOLLECTIONM. For heterogeneous (mixed-type) collections, you can use "GEOMETRY" as the type.

[Note]

This attribute is (probably) not part of the OpenGIS specification, but is required for ensuring type homogeneity.

4.4.3. Manually Registering Geometry Columns

Two of the cases where you may need this are the case of SQL Views and bulk inserts. For bulk insert case, you can correct the registration in the geometry_columns table by constraining the column or doing an alter table. For views, you could expose using a CAST operation. Note, if your column is typmod based, the creation process would register it correctly, so no need to do anything. Also views that have no spatial function applied to the geometry will register the same as the underlying table geometry column.

-- Lets say you have a view created like this
CREATE VIEW public.vwmytablemercator AS
        SELECT gid, ST_Transform(geom, 3395) As geom, f_name
        FROM public.mytable;

-- For it to register correctly
-- You need to cast the geometry
--
DROP VIEW public.vwmytablemercator;
CREATE VIEW  public.vwmytablemercator AS
        SELECT gid, ST_Transform(geom, 3395)::geometry(Geometry, 3395) As geom, f_name
        FROM public.mytable;

-- If you know the geometry type for sure is a 2D POLYGON then you could do
DROP VIEW public.vwmytablemercator;
CREATE VIEW  public.vwmytablemercator AS
        SELECT gid, ST_Transform(geom,3395)::geometry(Polygon, 3395) As geom, f_name
        FROM public.mytable;
--Lets say you created a derivative table by doing a bulk insert
SELECT poi.gid, poi.geom, citybounds.city_name
INTO myschema.my_special_pois
FROM poi INNER JOIN citybounds ON ST_Intersects(citybounds.geom, poi.geom);

-- Create 2D index on new table
CREATE INDEX idx_myschema_myspecialpois_geom_gist
  ON myschema.my_special_pois USING gist(geom);

-- If your points are 3D points or 3M points,
-- then you might want to create an nd index instead of a 2D index
CREATE INDEX my_special_pois_geom_gist_nd
        ON my_special_pois USING gist(geom gist_geometry_ops_nd);

-- To manually register this new table's geometry column in geometry_columns.
-- Note it will also change the underlying structure of the table to
-- to make the column typmod based.
SELECT populate_geometry_columns('myschema.my_special_pois'::regclass);

-- If you are using PostGIS 2.0 and for whatever reason, you
-- you need the constraint based definition behavior
-- (such as case of inherited tables where all children do not have the same type and srid)
-- set optional use_typmod argument to false
SELECT populate_geometry_columns('myschema.my_special_pois'::regclass, false); 

Although the old-constraint based method is still supported, a constraint-based geometry column used directly in a view, will not register correctly in geometry_columns, as will a typmod one. In this example we define a column using typmod and another using constraints.

CREATE TABLE pois_ny(gid SERIAL PRIMARY KEY, poi_name text, cat text, geom geometry(POINT,4326));
SELECT AddGeometryColumn('pois_ny', 'geom_2160', 2160, 'POINT', 2, false);

If we run in psql

\d pois_ny;

We observe they are defined differently -- one is typmod, one is constraint

Table "public.pois_ny"
  Column   |         Type          |                       Modifiers

-----------+-----------------------+------------------------------------------------------
 gid       | integer               | not null default nextval('pois_ny_gid_seq'::regclass)
 poi_name  | text                  |
 cat       | character varying(20) |
 geom      | geometry(Point,4326)  |
 geom_2160 | geometry              |
Indexes:
    "pois_ny_pkey" PRIMARY KEY, btree (gid)
Check constraints:
    "enforce_dims_geom_2160" CHECK (st_ndims(geom_2160) = 2)
    "enforce_geotype_geom_2160" CHECK (geometrytype(geom_2160) = 'POINT'::text
        OR geom_2160 IS NULL)
    "enforce_srid_geom_2160" CHECK (st_srid(geom_2160) = 2160)

In geometry_columns, they both register correctly

SELECT f_table_name, f_geometry_column, srid, type
        FROM geometry_columns
        WHERE f_table_name = 'pois_ny';
f_table_name | f_geometry_column | srid | type
-------------+-------------------+------+-------
pois_ny      | geom              | 4326 | POINT
pois_ny      | geom_2160         | 2160 | POINT

However -- if we were to create a view like this

CREATE VIEW vw_pois_ny_parks AS
SELECT *
  FROM pois_ny
  WHERE cat='park';

SELECT f_table_name, f_geometry_column, srid, type
        FROM geometry_columns
        WHERE f_table_name = 'vw_pois_ny_parks';

The typmod based geom view column registers correctly, but the constraint based one does not.

f_table_name   | f_geometry_column | srid |   type
------------------+-------------------+------+----------
 vw_pois_ny_parks | geom              | 4326 | POINT
 vw_pois_ny_parks | geom_2160         |    0 | GEOMETRY

This may change in future versions of PostGIS, but for now to force the constraint-based view column to register correctly, you need to do this:

DROP VIEW vw_pois_ny_parks;
CREATE VIEW vw_pois_ny_parks AS
SELECT gid, poi_name, cat,
  geom,
  geom_2160::geometry(POINT,2160) As geom_2160
  FROM pois_ny
  WHERE cat = 'park';
SELECT f_table_name, f_geometry_column, srid, type
        FROM geometry_columns
        WHERE f_table_name = 'vw_pois_ny_parks';
f_table_name   | f_geometry_column | srid | type
------------------+-------------------+------+-------
 vw_pois_ny_parks | geom              | 4326 | POINT
 vw_pois_ny_parks | geom_2160         | 2160 | POINT

4.5. Spatial Reference Systems

Spatial Reference Systems (SRS) define how geometry is referenced to locations on the Earth's surface.

4.5.1. SPATIAL_REF_SYS Table

The SPATIAL_REF_SYS table used by PostGIS is an OGC-compliant database table that defines the available spatial reference systems. It holds the numeric IDs and textual descriptions of the coordinate systems. The main use is to support transformation (reprojection) between them using ST_Transform.

The spatial_ref_sys table definition is:

CREATE TABLE spatial_ref_sys (
  srid       INTEGER NOT NULL PRIMARY KEY,
  auth_name  VARCHAR(256),
  auth_srid  INTEGER,
  srtext     VARCHAR(2048),
  proj4text  VARCHAR(2048)
)

The columns are:

srid

An integer code that uniquely identifies the Spatial Reference System (SRS) within the database.

auth_name

The name of the standard or standards body that is being cited for this reference system. For example, "EPSG" is a valid auth_name.

auth_srid

The ID of the Spatial Reference System as defined by the Authority cited in the auth_name. In the case of EPSG, this is where the EPSG projection code would go.

srtext

The Well-Known Text representation of the Spatial Reference System. An example of a WKT SRS representation is:

PROJCS["NAD83 / UTM Zone 10N",
  GEOGCS["NAD83",
        DATUM["North_American_Datum_1983",
          SPHEROID["GRS 1980",6378137,298.257222101]
        ],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]
  ],
  PROJECTION["Transverse_Mercator"],
  PARAMETER["latitude_of_origin",0],
  PARAMETER["central_meridian",-123],
  PARAMETER["scale_factor",0.9996],
  PARAMETER["false_easting",500000],
  PARAMETER["false_northing",0],
  UNIT["metre",1]
]

For a listing of EPSG projection codes and their corresponding WKT representations, see http://www.opengeospatial.org/. For a discussion of SRS WKT in general, see the OpenGIS "Coordinate Transformation Services Implementation Specification" at http://www.opengeospatial.org/standards. For information on the European Petroleum Survey Group (EPSG) and their database of spatial reference systems, see http://www.epsg.org.

proj4text

PostGIS uses the PROJ library to provide coordinate transformation capabilities. The proj4text column contains the PROJ coordinate definition string for a particular SRID. For example:

+proj=utm +zone=10 +ellps=clrk66 +datum=NAD27 +units=m

For more information see the PROJ web site. The spatial_ref_sys.sql file contains both srtext and proj4text definitions for all EPSG projections.

When retrieving spatial reference system definitions for use in transformations, PostGIS uses fhe following strategy:

  • If auth_name and auth_srid are present (non-NULL) use the PROJ SRS based on those entries (if one exists).

  • If srtext is present create a SRS using it, if possible.

  • If proj4text is present create a SRS using it, if possible.

4.5.2. User-Defined Spatial Reference Systems

The PostGIS spatial_ref_sys table contains over 3000 of the most common spatial reference system definitions that are handled by the PROJ projection library. But there are many coordinate systems that it does not contain. You can add SRS definitions to the table if you have the required information about the spatial reference system. Or, you can define your own custom spatial reference system if you are familiar with PROJ constructs. Keep in mind that most spatial reference systems are regional and have no meaning when used outside of the bounds they were intended for.

A resource for finding spatial reference systems not defined in the core set is http://spatialreference.org/

Some commonly used spatial reference systems are: 4326 - WGS 84 Long Lat, 4269 - NAD 83 Long Lat, 3395 - WGS 84 World Mercator, 2163 - US National Atlas Equal Area, and the 60 WGS84 UTM zones. UTM zones are one of the most ideal for measurement, but only cover 6-degree regions. (To determine which UTM zone to use for your area of interest, see the utmzone PostGIS plpgsql helper function.)

US states use State Plane spatial reference systems (meter or feet based) - usually one or 2 exists per state. Most of the meter-based ones are in the core set, but many of the feet-based ones or ESRI-created ones will need to be copied from spatialreference.org.

You can even define non-Earth-based coordinate systems, such as Mars 2000 This Mars coordinate system is non-planar (it's in degrees spheroidal), but you can use it with the geography type to obtain length and proximity measurements in meters instead of degrees.

Here is an example of loading a custom coordinate system using an unassigned SRID and the PROJ definition for a US-centric Lambert Conformal projection:

INSERT INTO spatial_ref_sys (srid, proj4text)
VALUES ( 990000,
  '+proj=lcc  +lon_0=-95 +lat_0=25 +lat_1=25 +lat_2=25 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs'
);

4.6. Geometry Validation

PostGIS is compliant with the Open Geospatial Consortium’s (OGC) OpenGIS Specifications. As such, many PostGIS methods require, or more accurately, assume that geometries that are operated on are both simple and valid. For example, it does not make sense to calculate the area of a polygon that has a hole defined outside of the polygon, or to construct a polygon from a non-simple boundary line.

According to the OGC Specifications, a simple geometry is one that has no anomalous geometric points, such as self intersection or self tangency and primarily refers to 0 or 1-dimensional geometries (i.e. [MULTI]POINT, [MULTI]LINESTRING). Geometry validity, on the other hand, primarily refers to 2-dimensional geometries (i.e. [MULTI]POLYGON) and defines the set of assertions that characterizes a valid polygon. The description of each geometric class includes specific conditions that further detail geometric simplicity and validity.

A POINT is inherently simple as a 0-dimensional geometry object.

MULTIPOINTs are simple if no two coordinates (POINTs) are equal (have identical coordinate values).

A LINESTRING is simple if it does not pass through the same POINT twice (except for the endpoints, in which case it is referred to as a linear ring and additionally considered closed).

(a)

(b)

(c)

(d)

(a) and (c) are simple LINESTRINGs, (b) and (d) are not.

A MULTILINESTRING is simple only if all of its elements are simple and the only intersection between any two elements occurs at POINTs that are on the boundaries of both elements.

(e)

(f)

(g)

(e) and (f) are simple MULTILINESTRINGs, (g) is not.

By definition, a POLYGON is always simple. It is valid if no two rings in the boundary (made up of an exterior ring and interior rings) cross. The boundary of a POLYGON may intersect at a POINT but only as a tangent (i.e. not on a line). A POLYGON may not have cut lines or spikes and the interior rings must be contained entirely within the exterior ring.

(h)

(i)

(j)

(k)

(l)

(m)

(h) and (i) are valid POLYGONs, (j-m) cannot be represented as single POLYGONs, but (j) and (m) could be represented as a valid MULTIPOLYGON.

A MULTIPOLYGON is valid if and only if all of its elements are valid and the interiors of no two elements intersect. The boundaries of any two elements may touch, but only at a finite number of POINTs.

(n)

(o)

(p)

(n) and (o) are not valid MULTIPOLYGONs. (p), however, is valid.

Most of the functions implemented by the GEOS library rely on the assumption that your geometries are valid as specified by the OpenGIS Simple Feature Specification. To check simplicity or validity of geometries you can use the ST_IsSimple() and ST_IsValid()

-- Typically, it doesn't make sense to check
-- for validity on linear features since it will always return TRUE.
-- But in this example, PostGIS extends the definition of the OGC IsValid
-- by returning false if a LineString has less than 2 *distinct* vertices.
gisdb=# SELECT
   ST_IsValid('LINESTRING(0 0, 1 1)'),
   ST_IsValid('LINESTRING(0 0, 0 0, 0 0)');

 st_isvalid | st_isvalid
------------+-----------
      t     |     f

By default, PostGIS does not apply this validity check on geometry input, because testing for validity needs lots of CPU time for complex geometries, especially polygons. If you do not trust your data sources, you can manually enforce such a check to your tables by adding a check constraint:

ALTER TABLE mytable
  ADD CONSTRAINT geometry_valid_check
        CHECK (ST_IsValid(the_geom));

If you encounter any strange error messages such as "GEOS Intersection() threw an error!" when calling PostGIS functions with valid input geometries, you likely found an error in either PostGIS or one of the libraries it uses, and you should contact the PostGIS developers. The same is true if a PostGIS function returns an invalid geometry for valid input.

[Note]

Strictly compliant OGC geometries cannot have Z or M values. The ST_IsValid() function won't consider higher dimensioned geometries invalid! Invocations of AddGeometryColumn() will add a constraint checking geometry dimensions, so it is enough to specify 2 there.

4.7. Loading Spatial Data

Once you have created a spatial table, you are ready to upload spatial data to the database. There are two built-in ways to get spatial data into a PostGIS/PostgreSQL database: using formatted SQL statements or using the Shapefile loader.

4.7.1. Using SQL to Load Data

If spatial data can be converted to a text representation (as either WKT or WKB), then using SQL might be the easiest way to get data into PostGIS. Data can be bulk-loaded into PostGIS/PostgreSQL by loading a text file of SQL INSERT statements using the psql SQL utility.

A SQL load file (roads.sql for example) might look like this:

BEGIN;
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (1,'LINESTRING(191232 243118,191108 243242)','Jeff Rd');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (2,'LINESTRING(189141 244158,189265 244817)','Geordie Rd');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (3,'LINESTRING(192783 228138,192612 229814)','Paul St');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (4,'LINESTRING(189412 252431,189631 259122)','Graeme Ave');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (5,'LINESTRING(190131 224148,190871 228134)','Phil Tce');
INSERT INTO roads (road_id, roads_geom, road_name)
  VALUES (6,'LINESTRING(198231 263418,198213 268322)','Dave Cres');
COMMIT;

The SQL file can be loaded into PostgreSQL using psql:

psql -d [database] -f roads.sql

4.7.2. Using the Shapefile Loader

The shp2pgsql data loader converts Shapefiles into SQL suitable for insertion into a PostGIS/PostgreSQL database either in geometry or geography format. The loader has several operating modes selected by command line flags.

There is also a shp2pgsql-gui graphical interface with most of the options as the command-line loader. This may be easier to use for one-off non-scripted loading or if you are new to PostGIS. It can also be configured as a plugin to PgAdminIII.

(c|a|d|p) These are mutually exclusive options:

-c

Creates a new table and populates it from the Shapefile. This is the default mode.

-a

Appends data from the Shapefile into the database table. Note that to use this option to load multiple files, the files must have the same attributes and same data types.

-d

Drops the database table before creating a new table with the data in the Shapefile.

-p

Only produces the table creation SQL code, without adding any actual data. This can be used if you need to completely separate the table creation and data loading steps.

-?

Display help screen.

-D

Use the PostgreSQL "dump" format for the output data. This can be combined with -a, -c and -d. It is much faster to load than the default "insert" SQL format. Use this for very large data sets.

-s [<FROM_SRID>:]<SRID>

Creates and populates the geometry tables with the specified SRID. Optionally specifies that the input shapefile uses the given FROM_SRID, in which case the geometries will be reprojected to the target SRID.

-k

Keep identifiers' case (column, schema and attributes). Note that attributes in Shapefile are all UPPERCASE.

-i

Coerce all integers to standard 32-bit integers, do not create 64-bit bigints, even if the DBF header signature appears to warrant it.

-I

Create a GiST index on the geometry column.

-m

-m a_file_name Specify a file containing a set of mappings of (long) column names to 10 character DBF column names. The content of the file is one or more lines of two names separated by white space and no trailing or leading space. For example:

COLUMNNAME DBFFIELD1
AVERYLONGCOLUMNNAME DBFFIELD2

-S

Generate simple geometries instead of MULTI geometries. Will only succeed if all the geometries are actually single (I.E. a MULTIPOLYGON with a single shell, or or a MULTIPOINT with a single vertex).

-t <dimensionality>

Force the output geometry to have the specified dimensionality. Use the following strings to indicate the dimensionality: 2D, 3DZ, 3DM, 4D.

If the input has fewer dimensions that specified, the output will have those dimensions filled in with zeroes. If the input has more dimensions that specified, the unwanted dimensions will be stripped.

-w

Output WKT format, instead of WKB. Note that this can introduce coordinate drifts due to loss of precision.

-e

Execute each statement on its own, without using a transaction. This allows loading of the majority of good data when there are some bad geometries that generate errors. Note that this cannot be used with the -D flag as the "dump" format always uses a transaction.

-W <encoding>

Specify encoding of the input data (dbf file). When used, all attributes of the dbf are converted from the specified encoding to UTF8. The resulting SQL output will contain a SET CLIENT_ENCODING to UTF8 command, so that the backend will be able to reconvert from UTF8 to whatever encoding the database is configured to use internally.

-N <policy>

NULL geometries handling policy (insert*,skip,abort)

-n

-n Only import DBF file. If your data has no corresponding shapefile, it will automatically switch to this mode and load just the dbf. So setting this flag is only needed if you have a full shapefile set, and you only want the attribute data and no geometry.

-G

Use geography type instead of geometry (requires lon/lat data) in WGS84 long lat (SRID=4326)

-T <tablespace>

Specify the tablespace for the new table. Indexes will still use the default tablespace unless the -X parameter is also used. The PostgreSQL documentation has a good description on when to use custom tablespaces.

-X <tablespace>

Specify the tablespace for the new table's indexes. This applies to the primary key index, and the GIST spatial index if -I is also used.

-Z

When used, this flag will prevent the generation of ANALYZE statements. Without the -Z flag (default behaviour), the ANALYZE statements will be generated.

An example session using the loader to create an input file and loading it might look like this:

# shp2pgsql -c -D -s 4269 -i -I shaperoads.shp myschema.roadstable > roads.sql
# psql -d roadsdb -f roads.sql

A conversion and load can be done in one step using UNIX pipes:

# shp2pgsql shaperoads.shp myschema.roadstable | psql -d roadsdb

4.8. Extracting Spatial Data

Spatial data can be extracted from the database using either SQL or the Shapefile dumper. The section on SQL presents some of the functions available to do comparisons and queries on spatial tables.

4.8.1. Using SQL to Extract Data

The most straightforward way of extracting spatial data out of the database is to use a SQL SELECT query to define the data set to be extracted and dump the resulting columns into a parsable text file:

db=# SELECT road_id, ST_AsText(road_geom) AS geom, road_name FROM roads;

road_id | geom                                    | road_name
--------+-----------------------------------------+-----------
          1 | LINESTRING(191232 243118,191108 243242) | Jeff Rd
          2 | LINESTRING(189141 244158,189265 244817) | Geordie Rd
          3 | LINESTRING(192783 228138,192612 229814) | Paul St
          4 | LINESTRING(189412 252431,189631 259122) | Graeme Ave
          5 | LINESTRING(190131 224148,190871 228134) | Phil Tce
          6 | LINESTRING(198231 263418,198213 268322) | Dave Cres
          7 | LINESTRING(218421 284121,224123 241231) | Chris Way
(6 rows)

There will be times when some kind of restriction is necessary to cut down the number of records returned. In the case of attribute-based restrictions, use the same SQL syntax as used with a non-spatial table. In the case of spatial restrictions, the following functions are useful:

ST_Intersects

This function tells whether two geometries share any space.

=

This tests whether two geometries are geometrically identical. For example, if 'POLYGON((0 0,1 1,1 0,0 0))' is the same as 'POLYGON((0 0,1 1,1 0,0 0))' (it is).

Next, you can use these operators in queries. Note that when specifying geometries and boxes on the SQL command line, you must explicitly turn the string representations into geometries function. The 312 is a fictitious spatial reference system that matches our data. So, for example:

SELECT road_id, road_name
  FROM roads
  WHERE roads_geom='SRID=312;LINESTRING(191232 243118,191108 243242)'::geometry;

The above query would return the single record from the "ROADS_GEOM" table in which the geometry was equal to that value.

To check whether some of the roads passes in the area defined by a polygon:

SELECT road_id, road_name
FROM roads
WHERE ST_Intersects(roads_geom, 'SRID=312;POLYGON((...))');

The most common spatial query will probably be a "frame-based" query, used by client software, like data browsers and web mappers, to grab a "map frame" worth of data for display.

When using the "&&" operator, you can specify either a BOX3D as the comparison feature or a GEOMETRY. When you specify a GEOMETRY, however, its bounding box will be used for the comparison.

Using a "BOX3D" object for the frame, such a query looks like this:

SELECT ST_AsText(roads_geom) AS geom
FROM roads
WHERE
  roads_geom && ST_MakeEnvelope(191232, 243117,191232, 243119,312);

Note the use of the SRID 312, to specify the projection of the envelope.

4.8.2. Using the Shapefile Dumper

The pgsql2shp table dumper connects to the database and converts a table (possibly defined by a query) into a shape file. The basic syntax is:

pgsql2shp [<options>] <database> [<schema>.]<table>
pgsql2shp [<options>] <database> <query>

The commandline options are:

-f <filename>

Write the output to a particular filename.

-h <host>

The database host to connect to.

-p <port>

The port to connect to on the database host.

-P <password>

The password to use when connecting to the database.

-u <user>

The username to use when connecting to the database.

-g <geometry column>

In the case of tables with multiple geometry columns, the geometry column to use when writing the shape file.

-b

Use a binary cursor. This will make the operation faster, but will not work if any NON-geometry attribute in the table lacks a cast to text.

-r

Raw mode. Do not drop the gid field, or escape column names.

-m filename

Remap identifiers to ten character names. The content of the file is lines of two symbols separated by a single white space and no trailing or leading space: VERYLONGSYMBOL SHORTONE ANOTHERVERYLONGSYMBOL SHORTER etc.

4.9. Building Spatial Indexes

Indexes make using a spatial database for large data sets possible. Without indexing, a search for features would require a sequential scan of every record in the database. Indexing speeds up searching by organizing the data into a structure which can be quickly traversed to find records.

The B-tree index method commonly used for attribute data is not very useful for spatial data, since it only supports storing and querying data in a single dimension. Data such as geometry which has 2 or more dimensions) requires an index method that supports range query across all the data dimensions. (That said, it is possible to effectively index so-called XY (point) data using a B-tree and explict range searches.) One of the key advantages of PostgreSQL for spatial data handling is that it offers several kinds of index methods which work well for multi-dimensional data: GiST, BRIN and SP-GiST indexes.

  • GiST (Generalized Search Tree) indexes break up data into "things to one side", "things which overlap", "things which are inside" and can be used on a wide range of data-types, including GIS data. PostGIS uses an R-Tree index implemented on top of GiST to index spatial data. GiST is the most commonly-used and versatile spatial index method, and offers very good query performance.

  • BRIN (Block Range Index) indexes operate by summarizing the spatial extent of ranges of table records. Search is done via a scan of the ranges. BRIN is only appropriate for use for some kinds of data (spatially sorted, with infrequent or no update). But it provides much faster index create time, and much smaller index size.

  • SP-GiST (Space-Partitioned Generalized Search Tree) is a generic index method that supports partitioned search trees such as quad-trees, k-d trees, and radix trees (tries).

For more information see the PostGIS Workshop, and the PostgreSQL manual.

4.9.1. GiST Indexes

GiST stands for "Generalized Search Tree" and is a generic form of indexing for multi-dimensional data. PostGIS uses an R-Tree index implemented on top of GiST to index spatial data. GiST is the most commonly-used and versatile spatial index method, and offers very good query performance. Other implementations of GiST are used to speed up searches on all kinds of irregular data structures (integer arrays, spectral data, etc) which are not amenable to normal B-Tree indexing. For more information see the PostgreSQL manual.

Once a spatial data table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data (unless all your searches are based on attributes, in which case you'll want to build a normal index on the attribute fields).

The syntax for building a GiST index on a "geometry" column is as follows:

CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometryfield] ); 

The above syntax will always build a 2D-index. To get the an n-dimensional index for the geometry type, you can create one using this syntax:

CREATE INDEX [indexname] ON [tablename] USING GIST ([geometryfield] gist_geometry_ops_nd);

Building a spatial index is a computationally intensive exercise. It also blocks write access to your table for the time it creates, so on a production system you may want to do in in a slower CONCURRENTLY-aware way:

CREATE INDEX CONCURRENTLY [indexname] ON [tablename] USING GIST ( [geometryfield] ); 

After building an index, it is sometimes helpful to force PostgreSQL to collect table statistics, which are used to optimize query plans:

VACUUM ANALYZE [table_name] [(column_name)];

4.9.2. BRIN Indexes

BRIN stands for "Block Range Index". It is a general-purpose index method introduced in PostgreSQL 9.5. BRIN is a lossy index method, meaning that a secondary check is required to confirm that a record matches a given search condition (which is the case for all provided spatial indexes). It provides much faster index creation and much smaller index size, with reasonable read performance. Its primary purpose is to support indexing very large tables on columns which have a correlation with their physical location within the table. In addition to spatial indexing, BRIN can speed up searches on various kinds of attribute data structures (integer, arrays etc). For more information see the PostgreSQL manual.

Once a spatial table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data. GiST indexes are very performant as long as their size doesn't exceed the amount of RAM available for the database, and as long as you can afford the index storage size, and the cost of index update on write. Otherwise, for very large tables BRIN index can be considered as an alternative.

A BRIN index stores the bounding box enclosing all the geometries contained in the rows in a contiguous set of table blocks, called a block range. When executing a query using the index the block ranges are scanned to find the ones that intersect the query extent. This is efficient only if the data is physically ordered so that the bounding boxes for block ranges have minimal overlap (and ideally are mutually exclusive). The resulting index is very small in size, but is typically less performant for read than a GiST index over the same data.

Building a BRIN index is much less CPU-intensive than building a GiST index. It's common to find that a BRIN index is ten times faster to build than a GiST index over the same data. And because a BRIN index stores only one bounding box for each range of table blocks, it's common to use up to a thousand times less disk space than a GiST index.

You can choose the number of blocks to summarize in a range. If you decrease this number, the index will be bigger but will probably provide better performance.

For BRIN to be effective, the table data should be stored in a physical order which minimizes the amount of block extent overlap. It may be that the data is already sorted appropriately (for instance, if it is loaded from another dataset that is already sorted in spatial order). Otherwise, this can be accomplished by sorting the data by a one-dimensional spatial key. One way to do this is to create a new table sorted by the geometry values (which in recent PostGIS versions uses an efficient Hilbert curve ordering):

CREATE TABLE table_sorted AS
   SELECT * FROM table  ORDER BY geom;

Alternatively, data can be sorted in-place by using a GeoHash as a (temporary) index, and clustering on that index:

CREATE INDEX idx_temp_geohash ON table
    USING btree (ST_GeoHash( ST_Transform( geom, 4326 ), 20));
CLUSTER table USING idx_temp_geohash;

The syntax for building a BRIN index on a geometry column is:

CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geome_col] ); 

The above syntax builds a 2D index. To build a 3D-dimensional index, use this syntax:

CREATE INDEX [indexname] ON [tablename]
    USING BRIN ([geome_col] brin_geometry_inclusion_ops_3d);

You can also get a 4D-dimensional index using the 4D operator class:

CREATE INDEX [indexname] ON [tablename]
    USING BRIN ([geome_col] brin_geometry_inclusion_ops_4d);

The above commands use the default number of blocks in a range, which is 128. To specify the number of blocks to summarise in a range, use this syntax

CREATE INDEX [indexname] ON [tablename]
    USING BRIN ( [geome_col] ) WITH (pages_per_range = [number]); 

Keep in mind that a BRIN index only stores one index entry for a large number of rows. If your table stores geometries with a mixed number of dimensions, it's likely that the resulting index will have poor performance. You can avoid this performance penalty by choosing the operator class with the least number of dimensions of the stored geometries

The geography datatype is supported for BRIN indexing. The syntax for building a BRIN index on a geography column is:

CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geog_col] ); 

The above syntax builds a 2D-index for geospatial objects on the spheroid.

Currently, only "inclusion support" is provided, meaning that just the &&, ~ and @ operators can be used for the 2D cases (for both geometry and geography), and just the &&& operator for 3D geometries. There is currently no support for kNN searches.

An important difference between BRIN and other index types is that the database does not maintain the index dynamically. Changes to spatial data in the table are simply appended to the end of the index. This will cause index search performance to degrade over time. The index can be updated by performing a VACUUM, or by using a special function brin_summarize_new_values(regclass). For this reason BRIN may be most appropriate for use with data that is read-only, or only rarely changing. For more information refer to the manual.

To summarize using BRIN for spatial data:

  • Index build time is very fast, and index size is very small.

  • Index query time is slower than GiST, but can still be very acceptable.

  • Requires table data to be sorted in a spatial ordering.

  • Requires manual index maintenance.

  • Most appropriate for very large tables, with low or no overlap (e.g. points), which are static or change infrequently.

  • More effective for queries which return relatively large numbers of data records.

4.9.3. SP-GiST Indexes

SP-GiST stands for "Space-Partitioned Generalized Search Tree" and is a generic form of indexing for multi-dimensional data types that supports partitioned search trees, such as quad-trees, k-d trees, and radix trees (tries). The common feature of these data structures is that they repeatedly divide the search space into partitions that need not be of equal size. In addition to spatial indexing, SP-GiST is used to speed up searches on many kinds of data, such as phone routing, ip routing, substring search, etc. For more information see the PostgreSQL manual.

As it is the case for GiST indexes, SP-GiST indexes are lossy, in the sense that they store the bounding box enclosing spatial objects. SP-GiST indexes can be considered as an alternative to GiST indexes. The performance tests reveal that SP-GiST indexes are especially beneficial when there are many overlapping objects, that is, with so-called “spaghetti data”.

Once a GIS data table exceeds a few thousand rows, an SP-GiST index may be used to speed up spatial searches of the data. The syntax for building an SP-GiST index on a "geometry" column is as follows:

CREATE INDEX [indexname] ON [tablename] USING SPGIST ( [geometryfield] ); 

The above syntax will build a 2-dimensional index. A 3-dimensional index for the geometry type can be created using the 3D operator class:

CREATE INDEX [indexname] ON [tablename] USING SPGIST ([geometryfield] spgist_geometry_ops_3d);

Building a spatial index is a computationally intensive operation. It also blocks write access to your table for the time it creates, so on a production system you may want to do in in a slower CONCURRENTLY-aware way:

CREATE INDEX CONCURRENTLY [indexname] ON [tablename] USING SPGIST ( [geometryfield] ); 

After building an index, it is sometimes helpful to force PostgreSQL to collect table statistics, which are used to optimize query plans:

VACUUM ANALYZE [table_name] [(column_name)];

An SP-GiST index can accelerate queries involving the following operators:

  • <<, &<, &>, >>, <<|, &<|, |&>, |>>, &&, @>, <@, and ~=, for 2-dimensional indexes,

  • &/&, ~==, @>>, and <<@, for 3-dimensional indexes.

There is no support for kNN searches at the moment.

4.9.4. Tuning Index Usage

Ordinarily, indexes invisibly speed up data access: once an index is built, the PostgreSQL query planner automatically decides when to use it to improve query performance. But there are some situations where the planner does not choose to use existing indexes, so queries end up using slow sequential scans instead of a spatial index.

If you find your spatial indexes are not being used, there are a few things you can do:

  • Examine the query plan and check your query actually computes the thing you need. An erroneous JOIN, either forgotten or to the wrong table, can unexpectedly retrieve table records multiple times. To get the query plan, execute with EXPLAIN in front of the query.

  • Make sure statistics are gathered about the number and distributions of values in a table, to provide the query planner with better information to make decisions around index usage. VACUUM ANALYZE will compute both.

    You should regularly vacuum your databases anyways. Many PostgreSQL DBAs run VACUUM as an off-peak cron job on a regular basis.

  • If vacuuming does not help, you can temporarily force the planner to use the index information by using the command SET ENABLE_SEQSCAN TO OFF;. This way you can check whether the planner is at all able to generate an index-accelerated query plan for your query. You should only use this command for debugging; generally speaking, the planner knows better than you do about when to use indexes. Once you have run your query, do not forget to run SET ENABLE_SEQSCAN TO ON; so that the planner will operate normally for other queries.

  • If SET ENABLE_SEQSCAN TO OFF; helps your query to run faster, your Postgres is likely not tuned for your hardware. If you find the planner wrong about the cost of sequential versus index scans try reducing the value of RANDOM_PAGE_COST in postgresql.conf, or use SET RANDOM_PAGE_COST TO 1.1;. The default value for RANDOM_PAGE_COST is 4.0. Try setting it to 1.1 (for SSD) or 2.0 (for fast magnetic disks). Decreasing the value makes the planner more likely to use index scans.

  • If SET ENABLE_SEQSCAN TO OFF; does not help your query, the query may be using a SQL construct that the Postgres planner is not yet able to optimize. It may be possible to rewrite the query in a way that the planner is able to handle. For example, a subquery with an inline SELECT may not produce an efficient plan, but could possibly be rewritten using a LATERAL JOIN.

For more information see the Postgres manual section on Query Planning.

Chapter 5. Spatial Queries

The raison d'etre of spatial databases is to perform queries inside the database which would ordinarily require desktop GIS functionality. Using PostGIS effectively requires knowing what spatial functions are available, how to use them in queries, and ensuring that appropriate indexes are in place to provide good performance.

5.1. Determining Spatial Relationships

Spatial relationships indicate how two geometries interact with one another. They are a fundamental capability for querying geometry.

5.1.1. Dimensionally Extended 9-Intersection Model

According to the OpenGIS Simple Features Implementation Specification for SQL, "the basic approach to comparing two geometries is to make pair-wise tests of the intersections between the Interiors, Boundaries and Exteriors of the two geometries and to classify the relationship between the two geometries based on the entries in the resulting 'intersection' matrix."

In the theory of point-set topology, the points in a geometry embedded in 2-dimensional space are categorized into three sets:

Boundary

The boundary of a geometry is the set of geometries of the next lower dimension. For POINTs, which have a dimension of 0, the boundary is the empty set. The boundary of a LINESTRING is the two endpoints. For POLYGONs, the boundary is the linework of the exterior and interior rings.

Interior

The interior of a geometry are those points of a geometry that are not in the boundary. For POINTs, the interior is the point itself. The interior of a LINESTRING is the set of points between the endpoints. For POLYGONs, the interior is the areal surface inside the polygon.

Exterior

The exterior of a geometry is the rest of the space in which the geometry is embedded; in other words, all points not in the interior or on the boundary of the geometry. It is a 2-dimensional non-closed surface.

The Dimensionally Extended 9-Intersection Model (DE-9IM) describes the spatial relationship between two geometries by specifying the dimensions of the 9 intersections between the above sets for each geometry. The intersection dimensions can be formally represented in a 3x3 intersection matrix.

For a geometry g the Interior, Boundary, and Exterior are denoted using the notation I(g), B(g), and E(g). Also, dim(s) denotes the dimension of a set s with the domain of {0,1,2,F}:

  • 0 => point

  • 1 => line

  • 2 => area

  • F => empty set

Using this notation, the intersection matrix for two geometries a and b is:

 InteriorBoundaryExterior
Interiordim( I(a) ∩ I(b) )dim( I(a) ∩ B(b) )dim( I(a) ∩ E(b) )
Boundarydim( B(a) ∩ I(b) )dim( B(a) ∩ B(b) )dim( B(a) ∩ E(b) )
Exteriordim( E(a) ∩ I(b) )dim( E(a) ∩ B(b) )dim( E(a) ∩ E(b) )

Visually, for two overlapping polygonal geometries, this looks like:

 

 InteriorBoundaryExterior
Interior

dim( I(a) ∩ I(b) ) = 2

dim( I(a) ∩ B(b) = 1

dim( I(a) ∩ E(b) ) = 2

Boundary

dim( B(a) ∩ I(b) ) = 1

dim( B(a) ∩ B(b) ) = 0

dim( B(a) ∩ E(b) ) = 1

Exterior

dim( E(a) ∩ I(b) ) = 2

dim( E(a) ∩ B(b) ) = 1

dim( E(a) ∩ E(b) = 2

Reading from left to right and top to bottom, the intersection matrix is represented as the text string '212101212'.

For more information, refer to:

5.1.2. Named Spatial Relationships

To make it easy to determine common spatial relationships, the OGC SFS defines a set of named spatial relationship predicates. PostGIS provides these as the functions ST_Contains, ST_Crosses, ST_Disjoint, ST_Equals, ST_Intersects, ST_Overlaps, ST_Touches, ST_Within. It also defines the non-standard relationship predicates ST_Covers, ST_CoveredBy, and ST_ContainsProperly.

Spatial predicates are usually used as conditions in SQL WHERE or JOIN clauses. The named spatial predicates automatically use a spatial index if one is available, so there is no need to use the bounding box operator && as well. For example:

SELECT city.name, state.name, city.geom
FROM city JOIN state ON ST_Intersects(city.geom, state.geom);

For more details and illustrations, see the PostGIS Workshop.

5.1.3. General Spatial Relationships

In some cases the named spatial relationships are insufficient to provide a desired spatial filter condition.

For example, consider a linear dataset representing a road network. It may be required to identify all road segments that cross each other, not at a point, but in a line (perhaps to validate some business rule). In this case ST_Crosses does not provide the necessary spatial filter, since for linear features it returns true only where they cross at a point.

A two-step solution would be to first compute the actual intersection (ST_Intersection) of pairs of road lines that spatially intersect (ST_Intersects), and then check if the intersection's ST_GeometryType is 'LINESTRING' (properly dealing with cases that return GEOMETRYCOLLECTIONs of [MULTI]POINTs, [MULTI]LINESTRINGs, etc.).

Clearly, a simpler and faster solution is desirable.

A second example is locating wharves that intersect a lake's boundary on a line and where one end of the wharf is up on shore. In other words, where a wharf is within but not completely contained by a lake, intersects the boundary of a lake on a line, and where exactly one of the wharf's endpoints is within or on the boundary of the lake. It is possible to use a combination of spatial predicates to find the required features:

These requirements can be met by computing the full DE-9IM intersection matrix. PostGIS provides the ST_Relate function to do this:

SELECT ST_Relate( 'LINESTRING (1 1, 5 5)',
                  'POLYGON ((3 3, 3 7, 7 7, 7 3, 3 3))' );
st_relate
-----------
1010F0212

To test a particular spatial relationship, an intersection matrix pattern is used. This is the matrix representation augmented with the additional symbols {T,*}:

  • T => intersection dimension is non-empty; i.e. is in {0,1,2}

  • * => don't care

Using intersection matrix patterns, specific spatial relationships can be evaluated in a more succinct way. The ST_Relate and the ST_RelateMatch functions can be used to test intersection matrix patterns. For the first example above, the intersection matrix pattern specifying two lines intersecting in a line is '1*1***1**':

-- Find road segments that intersect in a line
SELECT a.id
FROM roads a, roads b
WHERE a.id != b.id
      AND a.geom && b.geom
      AND ST_Relate(a.geom, b.geom, '1*1***1**');

For the second example, the intersection matrix pattern specifying a line partly inside and partly outside a polygon is '102101FF2':

-- Find wharves partly on a lake's shoreline
SELECT a.lake_id, b.wharf_id
FROM lakes a, wharfs b
WHERE a.geom && b.geom
      AND ST_Relate(a.geom, b.geom, '102101FF2');

5.2. Using Spatial Indexes

When constructing queries using spatial conditions, for best performance it is important to ensure that a spatial index is used, if one exists (see Section 4.9, “Building Spatial Indexes”). To do this, a spatial operator or index-aware function must be used in a WHERE or ON clause of the query.

Spatial operators include the bounding box operators (of which the most commonly used is &&; see Section 8.10.1, “Bounding Box Operators” for the full list) and the distance operators used in nearest-neighbour queries (the most common being <->; see Section 8.10.2, “Operatori” for the full list.)

Index-aware functions automatically add a bounding box operator to the spatial condition. Index-aware functions include the named spatial relationship predicates ST_Contains, ST_ContainsProperly, ST_CoveredBy, ST_Covers, ST_Crosses, ST_Intersects, ST_Overlaps, ST_Touches, ST_Within, ST_Within, and ST_3DIntersects, and the distance predicates ST_DWithin, ST_DFullyWithin, ST_3DDFullyWithin, and ST_3DDWithin .)

Functions such as ST_Distance do not use indexes to optimize their operation. For example, the following query would be quite slow on a large table:

SELECT geom
FROM geom_table
WHERE ST_Distance( geom, 'SRID=312;POINT(100000 200000)' ) < 100

This query selects all the geometries in geom_table which are within 100 units of the point (100000, 200000). It will be slow because it is calculating the distance between each point in the table and the specified point, ie. one ST_Distance() calculation is computed for every row in the table.

The number of rows processed can be reduced substantially by using the index-aware function ST_DWithin:

SELECT geom
FROM geom_table
WHERE ST_DWithin( geom, 'SRID=312;POINT(100000 200000)', 100 )

This query selects the same geometries, but it does it in a more efficient way. This is enabled by ST_DWithin() using the && operator internally on an expanded bounding box of the query geometry. If there is a spatial index on the_geom, the query planner will recognize that it can use the index to reduce the number of rows scanned before calculating the distance. The spatial index allows retrieving only records with geometries whose bounding boxes overlap the expanded extent and hence which might be within the required distance. The actual distance is then computed to confirm whether to include the record in the result set.

5.3. Examples of Spatial SQL

The examples in this section will make use of two tables, a table of linear roads, and a table of polygonal municipality boundaries. The table definitions for the bc_roads table is:

Column      | Type              | Description
------------+-------------------+-------------------
gid         | integer           | Unique ID
name        | character varying | Road Name
the_geom    | geometry          | Location Geometry (Linestring)

The table definition for the bc_municipality table is:

Column     | Type              | Description
-----------+-------------------+-------------------
gid        | integer           | Unique ID
code       | integer           | Unique ID
name       | character varying | City / Town Name
the_geom   | geometry          | Location Geometry (Polygon)
5.3.1. What is the total length of all roads, expressed in kilometers?
5.3.2. How large is the city of Prince George, in hectares?
5.3.3. What is the largest municipality in the province, by area?
5.3.4. What is the length of roads fully contained within each municipality?
5.3.5. Create a new table with all the roads within the city of Prince George.
5.3.6. What is the length in kilometers of "Douglas St" in Victoria?
5.3.7. What is the largest municipality polygon that has a hole?

5.3.1.

What is the total length of all roads, expressed in kilometers?

You can answer this question with a very simple piece of SQL:

SELECT sum(ST_Length(the_geom))/1000 AS km_roads FROM bc_roads;

km_roads
------------------
70842.1243039643
(1 row)

5.3.2.

How large is the city of Prince George, in hectares?

This query combines an attribute condition (on the municipality name) with a spatial calculation (of the area):

SELECT
  ST_Area(the_geom)/10000 AS hectares
FROM bc_municipality
WHERE name = 'PRINCE GEORGE';

hectares
------------------
32657.9103824927
(1 row)

5.3.3.

What is the largest municipality in the province, by area?

This query brings a spatial measurement into the query condition. There are several ways of approaching this problem, but the most efficient is below:

SELECT
  name,
  ST_Area(the_geom)/10000 AS hectares
FROM
  bc_municipality
ORDER BY hectares DESC
LIMIT 1;

name           | hectares
---------------+-----------------
TUMBLER RIDGE  | 155020.02556131
(1 row)

Note that in order to answer this query we have to calculate the area of every polygon. If we were doing this a lot it would make sense to add an area column to the table that we could separately index for performance. By ordering the results in a descending direction, and them using the PostgreSQL "LIMIT" command we can easily pick off the largest value without using an aggregate function like max().

5.3.4.

What is the length of roads fully contained within each municipality?

This is an example of a "spatial join", because we are bringing together data from two tables (doing a join) but using a spatial interaction condition ("contained") as the join condition rather than the usual relational approach of joining on a common key:

SELECT
  m.name,
  sum(ST_Length(r.the_geom))/1000 as roads_km
FROM
  bc_roads AS r,
  bc_municipality AS m
WHERE
  ST_Contains(m.the_geom, r.the_geom)
GROUP BY m.name
ORDER BY roads_km;

name                        | roads_km
----------------------------+------------------
SURREY                      | 1539.47553551242
VANCOUVER                   | 1450.33093486576
LANGLEY DISTRICT            | 833.793392535662
BURNABY                     | 773.769091404338
PRINCE GEORGE               | 694.37554369147
...

This query takes a while, because every road in the table is summarized into the final result (about 250K roads for our particular example table). For smaller overlays (several thousand records on several hundred) the response can be very fast.

5.3.5.

Create a new table with all the roads within the city of Prince George.

This is an example of an "overlay", which takes in two tables and outputs a new table that consists of spatially clipped or cut resultants. Unlike the "spatial join" demonstrated above, this query actually creates new geometries. An overlay is like a turbo-charged spatial join, and is useful for more exact analysis work:

CREATE TABLE pg_roads as
SELECT
  ST_Intersection(r.the_geom, m.the_geom) AS intersection_geom,
  ST_Length(r.the_geom) AS rd_orig_length,
  r.*
FROM
  bc_roads AS r,
  bc_municipality AS m
WHERE
  m.name = 'PRINCE GEORGE'
        AND ST_Intersects(r.the_geom, m.the_geom);

5.3.6.

What is the length in kilometers of "Douglas St" in Victoria?

SELECT
  sum(ST_Length(r.the_geom))/1000 AS kilometers
FROM
  bc_roads r,
  bc_municipality m
WHERE
        r.name = 'Douglas St'
        AND m.name = 'VICTORIA'
        AND ST_Intersects(m.the_geom, r.the_geom);

kilometers
------------------
4.89151904172838
(1 row)

5.3.7.

What is the largest municipality polygon that has a hole?

SELECT gid, name, ST_Area(the_geom) AS area
FROM bc_municipality
WHERE ST_NRings(the_geom) > 1
ORDER BY area DESC LIMIT 1;

gid  | name         | area
-----+--------------+------------------
12   | SPALLUMCHEEN | 257374619.430216
(1 row)

Chapter 6. Consigli per migliori prestazioni

6.1. Piccole tabelle contenenti geometrie di grandi dimensioni

6.1.1. Descrizione del problema

Le attuali versioni di PostgreSQL (compresa la versione 8.0) sono affette da un difetto del query optimizer riguardante le tabelle TOAST. Le tabelle TOAST sono una sorta di "spazio aggiuntivo" usato per memorizzare valori di grandi dimensioni (nel senso di dimensioni dei dati) che non possono essere salvati in normali pagine (per esempio lunghi testi, immagini o geometrie con molti vertici). Vedi la documentazione PostgreSQL sulle tabelle TOAST per maggiori informazioni).

Il problema si presenta nel caso di tabelle contenenti geometrie di grandi dimensioni ma poche righe (per esempio una tabella contenente i confini di tutti gli stati europei ad alta risoluzione). In questo caso infatti la tabella in se è di piccole dimensioni ma usa molto spazio TOAST. Nel nostro esempio la tabella conteneva circa 80 righe e utilizzava solo 3 pagine di dati, ma la tabella TOAST ne utilizzava 8225.

Ora si lanci una query che usi l'operatore && e che [MATCHES] solo poche righe. Il

Per controllare se i propri dati sono interessati da questo bug, si può usare il comando PostgreSQL "EXPLAIN ANALYZE". Per maggiori informazioni e dettagli tecnici consultare il corrispondente thread sulla mailing list di PostgreSQL: http://archives.postgresql.org/pgsql-performance/2005-02/msg00030.php

and newer thread on PostGIS https://lists.osgeo.org/pipermail/postgis-devel/2017-June/026209.html

6.1.2. Possibili soluzioni

Gli sviluppatori di PostgreSQL stanno cercando di risolvere il problema rendendo la valutazione della query indipendente dalla tabella TOAST. Per ora ci sono due possibili soluzioni alternative:

La è forzare il query planner ad usare l'indice spaziale usando il comando "SET enable_seqscan TO off;" prima di lanciare la query. Questo comando impedisce al query planner di usare lo scan sequenziale della tabella se possibile e lo forza quindi ad usare l'indice GIST. Tuttavia il comando deve essere lanciato ad ogni connessione e, per evitare di confondere il query planner in altri casi, il parametro deve essere resettato dopo l'esecuzione della query interessata con il comando "SET enable_seqscan TO on;" .

Il secondo metodo è rendere lo scan sequenziale così veloce come il query planner si aspetta che sia. Questo può essere raggiunto aggiungendo una colonna addizionale in cui salvare la bounding box di ogni geometria. Nel nostro esempio i comandi sarebbero:

SELECT AddGeometryColumn('myschema','mytable','bbox','4326','GEOMETRY','2');
UPDATE mytable SET bbox = ST_Envelope(ST_Force_2d(the_geom));

Ora la query deve essere modificata in modo da usare l'operatore && con la colonna bbox piuttosto che con la colonna geom_column:

SELECT geom_column
FROM mytable
WHERE bbox && ST_SetSRID('BOX3D(0 0,1 1)'::box3d,4326);

Ovviamente la colonna bbox deve essere mantenuta attuale quando si modificano o si aggiungono geometrie. La via più semplice per fare questo sarebbe con un trigger, oppure l'applicazione può essere modificata in modo da attualizzare anche la colonna bbox oppure si può lanciare l'UPDATE precedente dopo ogni modifica.

6.2. CLUSTERing di indici geometrici

Per tabelle che vengono per lo più solo lette, e dove un singolo indice è usato dalla maggior parte delle query, PostgreSQL offre il comando CLUSTER. Questo comando riordina fisicamente le righe in modo che l'ordine corrisponda a quello dell'indice. Con questo metodo si migliorano le prestazioni per due motivi: primo, il numero delle ricerche nella tabella dei dati è ridotto drasticamente. Secondo, se i dati interessati dalla query sono concentrati in un piccolo intervallo sull'indice, il processo di mettere in cache sarà più efficiente perché le righe saranno distribuite all'interno di poche pagine. (si invita a leggere la documentazione di PostgreSQL riguardante il comando CLUSTER).

Attualmente però, PostgreSQL non permette di usare il clustering con indici GIST, perché gli indici GIST ignorano i valori nulli:

lwgeom=# CLUSTER my_geom_index ON my_table;
ERROR: cannot cluster when index access method does not handle null values
HINT: You may be able to work around this by marking column "the_geom" NOT NULL.

Come suggerito dal messaggio di errore, è possibile aggirare il problema aggiungendo un vincolo "NOT NULL" alla tabella:

lwgeom=# ALTER TABLE my_table ALTER COLUMN the_geom SET not null; 
ALTER TABLE

Ovviamente questo non funzionerà se la colonna the_geom già contiene valori nulli. Inoltre il vincolo dev'essere definito usando il comando precedente. Usare un vincolo CHECK del tipo "ALTER TABLE blubb ADD CHECK (geometry is not null);" non funzionerà.

6.3. Evitare la conversione della dimensione

A volte può accadere di avere dati in 3D o 4D, ma di accederli sempre usando funzioni che danno in output solo geometrie 2D come ST_AsText() oppure ST_AsBinary(). Queste funzioni processano internamente le geometrie eseguendo ST_Force2D() e questo può risultare in un peggioramento delle prestazioni significativo nel caso di geometrie di grandi dimensioni. Per evitare questo problema è consigliabile eliminare le dimensioni non utilizzate una volte e per sempre:

UPDATE mytable SET the_geom = ST_Force_2d(the_geom); 
VACUUM FULL ANALYZE mytable;

Se la colonna di tipo geometry è stata aggiunta usando la funzione AddGeometryColumn(), verrà creato anche un vincolo dimensionale sulla geometria. Per aggirare il vincolo sarà necessario cancellarlo. Ricorda di attualizzare il record nella tabella geometry_columns e di ricreare il vincolo successivamente.

Nel caso di grandi tabelle può essere sensato dividere l'UPDATE in porzioni più piccole, usando la clausola WHERE con la chiave primaria o un altro criterio flessibile per attualizzare solo una parte della tabella , ed eseguendo un semplice "VACUUM;" tra gli UPDATE. Questo accorgimento ridurrà drasticamente il bisogno lo spazio temporaneo sul disco. Inoltre, se la colonna geometrica contiene geometrie con diverse dimensioni, si può limitare l'UPDATE con "WHERE dimension(the_geom)>2", evitando così di riscrivere le geometrie che sono già in 2D.

Chapter 7. Building Applications

7.1. Using MapServer

The Minnesota MapServer is an internet web-mapping server which conforms to the OpenGIS Web Map Service specification.

7.1.1. Basic Usage

To use PostGIS with MapServer, you need to know how to configure MapServer, which is beyond the scope of this documentation. This section covers specific PostGIS issues and configuration details.

To use PostGIS with MapServer, you will need:

  • Version 0.6 or newer of PostGIS.

  • Version 3.5 or newer of MapServer.

MapServer accesses PostGIS/PostgreSQL data like any other PostgreSQL client, using the libpq interface. This means that MapServer can be installed on any machine with network access to the PostGIS server, and use PostGIS as a source of data. The faster the connection between the systems, the better.

  1. Compile and install MapServer, with whatever options you desire, including the "--with-postgis" configuration option.

  2. In your MapServer map file, add a PostGIS layer. For example:

    LAYER
      CONNECTIONTYPE postgis
      NAME "widehighways"
      # Connect to a remote spatial database
      CONNECTION "user=dbuser dbname=gisdatabase host=bigserver"
      PROCESSING "CLOSE_CONNECTION=DEFER"
      # Get the lines from the 'geom' column of the 'roads' table
      DATA "geom from roads using srid=4326 using unique gid"
      STATUS ON
      TYPE LINE
      # Of the lines in the extents, only render the wide highways
      FILTER "type = 'highway' and numlanes >= 4"
      CLASS
        # Make the superhighways brighter and 2 pixels wide
        EXPRESSION ([numlanes] >= 6)
        STYLE
          COLOR 255 22 22
          WIDTH 2
        END
      END
      CLASS
        # All the rest are darker and only 1 pixel wide
        EXPRESSION ([numlanes] < 6)
        STYLE
          COLOR 205 92 82
        END
      END
    END

    In the example above, the PostGIS-specific directives are as follows:

    CONNECTIONTYPE

    For PostGIS layers, this is always "postgis".

    CONNECTION

    The database connection is governed by the a 'connection string' which is a standard set of keys and values like this (with the default values in <>):

    user=<username> password=<password> dbname=<username> hostname=<server> port=<5432>

    An empty connection string is still valid, and any of the key/value pairs can be omitted. At a minimum you will generally supply the database name and username to connect with.

    DATA

    The form of this parameter is "<geocolumn> from <tablename> using srid=<srid> using unique <primary key>" where the column is the spatial column to be rendered to the map, the SRID is SRID used by the column and the primary key is the table primary key (or any other uniquely-valued column with an index).

    You can omit the "using srid" and "using unique" clauses and MapServer will automatically determine the correct values if possible, but at the cost of running a few extra queries on the server for each map draw.

    PROCESSING

    Putting in a CLOSE_CONNECTION=DEFER if you have multiple layers reuses existing connections instead of closing them. This improves speed. Refer to for MapServer PostGIS Performance Tips for a more detailed explanation.

    FILTER

    The filter must be a valid SQL string corresponding to the logic normally following the "WHERE" keyword in a SQL query. So, for example, to render only roads with 6 or more lanes, use a filter of "num_lanes >= 6".

  3. In your spatial database, ensure you have spatial (GiST) indexes built for any the layers you will be drawing.

    CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );
  4. If you will be querying your layers using MapServer you will also need to use the "using unique" clause in your DATA statement.

    MapServer requires unique identifiers for each spatial record when doing queries, and the PostGIS module of MapServer uses the unique value you specify in order to provide these unique identifiers. Using the table primary key is the best practice.

7.1.2. Frequently Asked Questions

7.1.2.1. When I use an EXPRESSION in my map file, the condition never returns as true, even though I know the values exist in my table.
7.1.2.2. The FILTER I use for my Shapefiles is not working for my PostGIS table of the same data.
7.1.2.3. My PostGIS layer draws much slower than my Shapefile layer, is this normal?
7.1.2.4. My PostGIS layer draws fine, but queries are really slow. What is wrong?
7.1.2.5. Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?

7.1.2.1.

When I use an EXPRESSION in my map file, the condition never returns as true, even though I know the values exist in my table.

Unlike shape files, PostGIS field names have to be referenced in EXPRESSIONS using lower case.

EXPRESSION ([numlanes] >= 6)

7.1.2.2.

The FILTER I use for my Shapefiles is not working for my PostGIS table of the same data.

Unlike shape files, filters for PostGIS layers use SQL syntax (they are appended to the SQL statement the PostGIS connector generates for drawing layers in MapServer).

FILTER "type = 'highway' and numlanes >= 4"

7.1.2.3.

My PostGIS layer draws much slower than my Shapefile layer, is this normal?

In general, the more features you are drawing into a given map, the more likely it is that PostGIS will be slower than Shapefiles. For maps with relatively few features (100s), PostGIS will often be faster. For maps with high feature density (1000s), PostGIS will always be slower.

If you are finding substantial draw performance problems, it is possible that you have not built a spatial index on your table.

postgis# CREATE INDEX geotable_gix ON geotable USING GIST ( geocolumn );
postgis# VACUUM ANALYZE;

7.1.2.4.

My PostGIS layer draws fine, but queries are really slow. What is wrong?

For queries to be fast, you must have a unique key for your spatial table and you must have an index on that unique key.

You can specify what unique key for mapserver to use with the USING UNIQUE clause in your DATA line:

DATA "geom FROM geotable USING UNIQUE gid"

7.1.2.5.

Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?

Yes! MapServer understands geography columns as being the same as geometry columns, but always using an SRID of 4326. Just make sure to include a "using srid=4326" clause in your DATA statement. Everything else works exactly the same as with geometry.

DATA "geog FROM geogtable USING SRID=4326 USING UNIQUE gid"

7.1.3. Advanced Usage

The USING pseudo-SQL clause is used to add some information to help mapserver understand the results of more complex queries. More specifically, when either a view or a subselect is used as the source table (the thing to the right of "FROM" in a DATA definition) it is more difficult for mapserver to automatically determine a unique identifier for each row and also the SRID for the table. The USING clause can provide mapserver with these two pieces of information as follows:

DATA "geom FROM (
  SELECT
    table1.geom AS geom,
    table1.gid AS gid,
    table2.data AS data
  FROM table1
  LEFT JOIN table2
  ON table1.id = table2.id
) AS new_table USING UNIQUE gid USING SRID=4326"
USING UNIQUE <uniqueid>

MapServer requires a unique id for each row in order to identify the row when doing map queries. Normally it identifies the primary key from the system tables. However, views and subselects don't automatically have an known unique column. If you want to use MapServer's query functionality, you need to ensure your view or subselect includes a uniquely valued column, and declare it with USING UNIQUE. For example, you could explicitly select nee of the table's primary key values for this purpose, or any other column which is guaranteed to be unique for the result set.

[Note]

"Querying a Map" is the action of clicking on a map to ask for information about the map features in that location. Don't confuse "map queries" with the SQL query in a DATA definition.

USING SRID=<srid>

PostGIS needs to know which spatial referencing system is being used by the geometries in order to return the correct data back to MapServer. Normally it is possible to find this information in the "geometry_columns" table in the PostGIS database, however, this is not possible for tables which are created on the fly such as subselects and views. So the USING SRID= option allows the correct SRID to be specified in the DATA definition.

7.1.4. Examples

Lets start with a simple example and work our way up. Consider the following MapServer layer definition:

LAYER
  CONNECTIONTYPE postgis
  NAME "roads"
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  DATA "geom from roads"
  STATUS ON
  TYPE LINE
  CLASS
    STYLE
      COLOR 0 0 0
    END
  END
END

This layer will display all the road geometries in the roads table as black lines.

Now lets say we want to show only the highways until we get zoomed in to at least a 1:100000 scale - the next two layers will achieve this effect:

LAYER
  CONNECTIONTYPE postgis
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  PROCESSING "CLOSE_CONNECTION=DEFER"
  DATA "geom from roads"
  MINSCALE 100000
  STATUS ON
  TYPE LINE
  FILTER "road_type = 'highway'"
  CLASS
    COLOR 0 0 0
  END
END
LAYER
  CONNECTIONTYPE postgis
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  PROCESSING "CLOSE_CONNECTION=DEFER"
  DATA "geom from roads"
  MAXSCALE 100000
  STATUS ON
  TYPE LINE
  CLASSITEM road_type
  CLASS
    EXPRESSION "highway"
    STYLE
      WIDTH 2
      COLOR 255 0 0
    END
  END
  CLASS
    STYLE
      COLOR 0 0 0
    END
  END
END

The first layer is used when the scale is greater than 1:100000, and displays only the roads of type "highway" as black lines. The FILTER option causes only roads of type "highway" to be displayed.

The second layer is used when the scale is less than 1:100000, and will display highways as double-thick red lines, and other roads as regular black lines.

So, we have done a couple of interesting things using only MapServer functionality, but our DATA SQL statement has remained simple. Suppose that the name of the road is stored in another table (for whatever reason) and we need to do a join to get it and label our roads.

LAYER
  CONNECTIONTYPE postgis
  CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"
  DATA "geom FROM (SELECT roads.gid AS gid, roads.geom AS geom,
        road_names.name as name FROM roads LEFT JOIN road_names ON
        roads.road_name_id = road_names.road_name_id)
        AS named_roads USING UNIQUE gid USING SRID=4326"
  MAXSCALE 20000
  STATUS ON
  TYPE ANNOTATION
  LABELITEM name
  CLASS
    LABEL
      ANGLE auto
      SIZE 8
      COLOR 0 192 0
      TYPE truetype
      FONT arial
    END
  END
END

This annotation layer adds green labels to all the roads when the scale gets down to 1:20000 or less. It also demonstrates how to use an SQL join in a DATA definition.

7.2. Java Clients (JDBC)

Java clients can access PostGIS "geometry" objects in the PostgreSQL database either directly as text representations or using the JDBC extension objects bundled with PostGIS. In order to use the extension objects, the "postgis.jar" file must be in your CLASSPATH along with the "postgresql.jar" JDBC driver package.

import java.sql.*;
import java.util.*;
import java.lang.*;
import org.postgis.*;

public class JavaGIS {

public static void main(String[] args) {

  java.sql.Connection conn;

  try {
    /*
    * Load the JDBC driver and establish a connection.
    */
    Class.forName("org.postgresql.Driver");
    String url = "jdbc:postgresql://localhost:5432/database";
    conn = DriverManager.getConnection(url, "postgres", "");
    /*
    * Add the geometry types to the connection. Note that you
    * must cast the connection to the pgsql-specific connection
    * implementation before calling the addDataType() method.
    */
    ((org.postgresql.PGConnection)conn).addDataType("geometry",Class.forName("org.postgis.PGgeometry"));
    ((org.postgresql.PGConnection)conn).addDataType("box3d",Class.forName("org.postgis.PGbox3d"));
    /*
    * Create a statement and execute a select query.
    */
    Statement s = conn.createStatement();
    ResultSet r = s.executeQuery("select geom,id from geomtable");
    while( r.next() ) {
      /*
      * Retrieve the geometry as an object then cast it to the geometry type.
      * Print things out.
      */
      PGgeometry geom = (PGgeometry)r.getObject(1);
      int id = r.getInt(2);
      System.out.println("Row " + id + ":");
      System.out.println(geom.toString());
    }
    s.close();
    conn.close();
  }
catch( Exception e ) {
  e.printStackTrace();
  }
}
}

The "PGgeometry" object is a wrapper object which contains a specific topological geometry object (subclasses of the abstract class "Geometry") depending on the type: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon.

PGgeometry geom = (PGgeometry)r.getObject(1);
if( geom.getType() == Geometry.POLYGON ) {
  Polygon pl = (Polygon)geom.getGeometry();
  for( int r = 0; r < pl.numRings(); r++) {
    LinearRing rng = pl.getRing(r);
    System.out.println("Ring: " + r);
    for( int p = 0; p < rng.numPoints(); p++ ) {
      Point pt = rng.getPoint(p);
      System.out.println("Point: " + p);
      System.out.println(pt.toString());
    }
  }
}

The JavaDoc for the extension objects provides a reference for the various data accessor functions in the geometric objects.

7.3. C Clients (libpq)

...

7.3.1. Text Cursors

...

7.3.2. Binary Cursors

...

Chapter 8. Guida a PostGIS

Le funzioni elencate sotto sono quelle di cui un utente PostGIS avrà più probabilmente bisogno. Ci sono altre funzioni, di supporto agli oggetti PostGIS, che non sono utili all'utente comune.

[Note]

PostGIS ha iniziato una transizione dalla namin convention esistente a una convenzione SQL-MM-centrica. Di conseguenza, molte funzioni di uso comune sono state rinominate usando il prefisso standard "spatial type" (ST). Le funzioni precedenti sono tuttora disponibili, anche se non elencate nel presente documento. Al loro posto sono presenti le funzioni aggiornate corrispondenti. Le funzioni non ST_ che mancano in questo documento sono deprecate e verranno eliminate in una futura release, quindi NON VANNO PIÙ USATE.

8.1. PostgreSQL PostGIS tipi Geometry/Geography/Box

Abstract

Questa sezione illustra i tipi di dati di PostgreSQL che vengono installati da Postgis. Vengono illustrati anche i metodi per eseguire il cast tra diversi tipi, cosa particolarmente importante per la realizzazione di funzioni proprie.

Each data type describes its type casting behaviour. A type cast converts values of one data type into another type. PostgreSQL allows defining casting behavior for custom types, along with the functions used to convert type values. Casts can have automatic behaviour, which allows automatic conversion of a function argument to a type supported by the function.

Some casts have explicit behaviour, which means the cast must be specified using the syntax CAST(myval As sometype) or myval::sometype. Explicit casting avoids the issue of ambiguous casts, which can occur when using an overloaded function which does not support a given type. For example, a function may accept a box2d or a box3d, but not a geometry. Since geometry has an automatic cast to both box types, this produces an "ambiguous function" error. To prevent the error use an explicit cast to the desired box type.

All data types can be cast to text, so this does not need to be specified explicitly.

box2d — Un parallelepipedo composto dalle coordinate xmin, ymin, zmin, xmax, ymax, zmax. Spesso usato per ritornare l'estensione 3D di una geometria o di una collezione di geometrie.
box3d — Un parallelepipedo composto dalle coordinate xmin, ymin, zmin, xmax, ymax, zmax. Spesso usato per ritornare l'estensione 3D di una geometria o di una collezione di geometrie.
geometry — geography è un tipo spaziale usato per rappresentare un'entità in un sistema di coordinate sferico valido per l'intero pianeta.
geometry_dump — A composite type used to describe the parts of complex geometry.
geography — The type representing spatial features with geodetic (ellipsoidal) coordinate systems.

Name

box2d — Un parallelepipedo composto dalle coordinate xmin, ymin, zmin, xmax, ymax, zmax. Spesso usato per ritornare l'estensione 3D di una geometria o di una collezione di geometrie.

Descrizione

box3d è un tipo spaziale di Postgis usato per rappresentare il parallelepipedo contente una geometria o un insieme di geometrie. La funzione ST_3DExtent ritorna un oggetto box3d.

The representation contains the values xmin, ymin, xmax, ymax. These are the minimum and maxium values of the X and Y extents.


Name

box3d — Un parallelepipedo composto dalle coordinate xmin, ymin, zmin, xmax, ymax, zmax. Spesso usato per ritornare l'estensione 3D di una geometria o di una collezione di geometrie.

Descrizione

box3d è un tipo spaziale di Postgis usato per rappresentare il parallelepipedo contente una geometria o un insieme di geometrie. La funzione ST_3DExtent ritorna un oggetto box3d.

The representation contains the values xmin, ymin, zmin, xmax, ymax, zmax. These are the minimum and maxium values of the X, Y and Z extents.

Comportamento in caso di CAST

Questa sezione illustra le modalità di CAST - automatici e espliciti - permessi per questo tipo di dato

Cast versoComportamento
boxautomatico
box2dautomatico
geometryautomatico

Name

geometry — geography è un tipo spaziale usato per rappresentare un'entità in un sistema di coordinate sferico valido per l'intero pianeta.

Descrizione

Il tipo di dato "geometry" è un fondamentale tipo spaziale di Postgis usato per rappresentare una entità in un sistema di coordinate euclideo.

All spatial operations on geometry use the units of the Spatial Reference System the geometry is in.

Comportamento in caso di CAST

Questa sezione illustra le modalità di CAST - automatici e espliciti - permessi per questo tipo di dato

Cast versoComportamento
boxautomatico
box2dautomatico
box3dautomatico
byteaautomatico
geographyautomatico
textautomatico

Name

geometry_dump — A composite type used to describe the parts of complex geometry.

Descrizione

geometry_dump is a composite data type containing the fields:

  • geom - a geometry representing a component of the dumped geometry. The geometry type depends on the originating function.

  • path[] - an integer array that defines the navigation path within the dumped geometry to the geom component. The path array is 1-based (i.e. path[1] is the first element.)

It is used by the ST_Dump* family of functions as an output type to explode a complex geometry into its constituent parts.


Name

geography — The type representing spatial features with geodetic (ellipsoidal) coordinate systems.

Descrizione

geography è un tipo spaziale usato per rappresentare un'entità in un sistema di coordinate sferico valido per l'intero pianeta.

Spatial operations on the geography type provide more accurate results by taking the ellipsoidal model into account.

Comportamento in caso di CAST

Questa sezione illustra le modalità di CAST - automatici e espliciti - permessi per questo tipo di dato

Cast versoComportamento
geometryEsplicito

8.2. Funzioni per la gestione del database

Abstract

These functions assist in defining tables containing geometry columns.

AddGeometryColumn — Rimuove una colonna geometry da una tabella spaziale
DropGeometryColumn — Rimuove una colonna geometry da una tabella spaziale
DropGeometryTable — Rimuove una tabella e tutte le sue referenze da geometry_columns
Find_SRID — Returns the SRID defined for a geometry column.
Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints.
UpdateGeometrySRID — Updates the SRID of all features in a geometry column, and the table metadata.

Name

AddGeometryColumn — Rimuove una colonna geometry da una tabella spaziale

Synopsis

text AddGeometryColumn(varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true);

text AddGeometryColumn(varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true);

text AddGeometryColumn(varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true);

Descrizione

Aggiunge una colonna di tipo geometry ad una tabella già esistente. schema_name è il nome dello schema contenente la tabella. srid deve essere un numero intero che si riferisce a un record presente nella tabella SPATIAL_REF_SYS. type deve essere una stringa corrispondente al tipo di geometria, per esempio 'POLYGON' oppure 'MULTILINESTRING'. La funzione produce un errore se lo schema non esiste (oppure non è visibile nel search_path attual), o la SRID specificata, il tipo di geometria o la dimensione sono invalidi.

[Note]

Cambiamento nella versione 2.0.0: questa funzione non aggiorna più geometry_columns perché geometry_columns non è più una tabella ma una vista che estrae automaticamente le informazioni necessarie dal system catalog. Inoltre per default la funzione non crea vincoli ma usa il modificatore di tipi integrato in PostgreSQL. Per esempio: creare una colonna con tipo POINT e con SRID 4326 con questa funzione, ora è equivalente a:ALTER TABLE some_table ADD COLUMN geom geometry(Point,4326);

Cambiamento nella versione 2.0.0: il vecchio funzionamento con i vincoli può essere attivato passando alla funzione l'argomento use_typmod impostato su false.

[Note]

Cambiamento in versione 2.0.0: le viste non possono più essere registrate in geometry_columns, a meno che le colonne geometry a cui fanno riferimento non siano state generate con typmod e usate senza funzioni wrapper. In questo caso la vista sarà registrata correttamente in geometry_columns perché eredita il typmod dalla colonna geometry originale. Le viste che usano funzioni che ritornano geometrie verranno registrate correttamente se il tipo delll'output della funzione verrà definito esplicitamente con la funzione CAST come typmod geometry.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Miglioramento nella version 2.0.0: introdotto il parametro use_typmod. Se settato su true (o se omesso) la funzione genererà una colonna geometry basata su typmod. Se settato su "false", la funzione genererà una colonna geometry con basata su vincoli geometrici.

Esempi

-- Creiamo uno schema in sui salvare i dati
CREATE SCHEMA my_schema;
-- Creiamo una Semplice tabella
CREATE TABLE my_schema.my_spatial_table (id serial);

-- La descrizione mostra una semplice tabella con un'unica colonna "id"
postgis=# \d my_schema.my_spatial_table
                                                         Table "my_schema.my_spatial_table"
 Column |  Type   |                                Modifiers
--------+---------+-------------------------------------------------------------------------
 id     | integer | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)

-- Aggiungiamo una colonna geometry
SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom',4326,'POINT',2);

-- Aggiungiamo un'altra colonna geometry settando il parametro use_typmod = false, 
-- generando quindo una colonna geometry basata su vincoli
SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom_c',4326,'POINT',2, false);

--Di nuovo aggiungiamo un'altra colonna geometry usando il vecchio meccanismo con vincoli
Add a curvepolygon using old constraint behavior
SELECT AddGeometryColumn ('my_schema','my_spatial_table','geomcp_c',4326,'CURVEPOLYGON',2, false);

-- Descriviamo di nuovo la tabella con le nuove 3 colonne geometry
\d my_schema.my_spatial_table
                            addgeometrycolumn                            
-------------------------------------------------------------------------
 my_schema.my_spatial_table.geomcp_c SRID:4326 TYPE:CURVEPOLYGON DIMS:2 
(1 row)

                                    Table "my_schema.my_spatial_table"
  Column  |         Type         |                                Modifiers                                
----------+----------------------+-------------------------------------------------------------------------
 id       | integer              | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)
 geom     | geometry(Point,4326) | 
 geom_c   | geometry             | 
 geomcp_c | geometry             | 
Check constraints:
    "enforce_dims_geom_c" CHECK (st_ndims(geom_c) = 2)
    "enforce_dims_geomcp_c" CHECK (st_ndims(geomcp_c) = 2)
    "enforce_geotype_geom_c" CHECK (geometrytype(geom_c) = 'POINT'::text OR geom_c IS NULL)
    "enforce_geotype_geomcp_c" CHECK (geometrytype(geomcp_c) = 'CURVEPOLYGON'::text OR geomcp_c IS NULL)
    "enforce_srid_geom_c" CHECK (st_srid(geom_c) = 4326)
    "enforce_srid_geomcp_c" CHECK (st_srid(geomcp_c) = 4326)
    
-- Le colonne geometry sono automaticamante registrate in geometry_columns
SELECT f_geometry_column As col_name, type, srid, coord_dimension As ndims 
    FROM geometry_columns
    WHERE f_table_name = 'my_spatial_table' AND f_table_schema = 'my_schema';

 col_name |     type     | srid | ndims 
----------+--------------+------+-------
 geom     | Point        | 4326 |     2
 geom_c   | Point        | 4326 |     2
 geomcp_c | CurvePolygon | 4326 |     2

Name

DropGeometryColumn — Rimuove una colonna geometry da una tabella spaziale

Synopsis

text DropGeometryColumn(varchar table_name, varchar column_name);

text DropGeometryColumn(varchar schema_name, varchar table_name, varchar column_name);

text DropGeometryColumn(varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name);

Descrizione

Rimuove una colonna geometry da una tabella spaziale. Il campo schema_name deve corrispondere al campo f_table_schema in geometry_columns.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Cambiamento nella versione 2.0.0: questa funzione è mantenuta per retrocompatibilità. Attualmente, essendo geometry_columns una vista basata sul system catalog, una colonna geometry può essere rimossa come qualsiasi altra colonna con ALTER TABLE

Esempi

SELECT DropGeometryColumn ('my_schema','my_spatial_table','geom');
                        ----RESULT output ---
                                          dropgeometrycolumn
------------------------------------------------------
 my_schema.my_spatial_table.geom effectively removed.
 
-- In PostGIS 2.0+ questo comando è equivalente al comando standard
-- alter table.  Ambedue i comandi rimuoveranno la colonna da geometry_columns
ALTER TABLE my_schema.my_spatial_table DROP column geom;
                

Name

DropGeometryTable — Rimuove una tabella e tutte le sue referenze da geometry_columns

Synopsis

boolean DropGeometryTable(varchar table_name);

boolean DropGeometryTable(varchar schema_name, varchar table_name);

boolean DropGeometryTable(varchar catalog_name, varchar schema_name, varchar table_name);

Descrizione

Rimuove una tabella spaziale e tutte le sue referenze da geometry_columns. Nota: utilizza la funzione PostgreSQL current_schema() se lo schema non è passato come argomento.

[Note]

Cambiamento nella versione 2.0.0: questa funzione è mantenuta per retrocompatibilità. Attualmente, essendo geometry_columns una vista basata sul system catalog, una tabella spaziale può essere rimossa come qualsiasi altra tabella con DROP TABLE

Esempi

SELECT DropGeometryTable ('my_schema','my_spatial_table');
----RESULT output ---
my_schema.my_spatial_table dropped.
                        
-- Il comando sopra è ora equivalente a --
DROP TABLE my_schema.my_spatial_table;
                

Name

Find_SRID — Returns the SRID defined for a geometry column.

Synopsis

text Populate_Geometry_Columns(boolean use_typmod=true);

int Populate_Geometry_Columns(oid relation_oid, boolean use_typmod=true);

Descrizione

Returns the integer SRID of the specified geometry column by searching through the GEOMETRY_COLUMNS table. If the geometry column has not been properly added (e.g. with the AddGeometryColumn function), this function will not work.

Esempi

SELECT Find_SRID('public', 'tiger_us_state_2007', 'the_geom_4269');
find_srid
----------
4269

Vedi anche

ST_SRID


Name

Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints.

Synopsis

text Populate_Geometry_Columns(boolean use_typmod=true);

int Populate_Geometry_Columns(oid relation_oid, boolean use_typmod=true);

Descrizione

Si accerta che le colonne geometry siano definite con typemod oppure abbiano gli appropriati vincoli spaziali e conseguentemente siano correttamente registrate nella vista geometry_columns. Per default la funzione converte tutte le colonne geometry definite senza typemod in geometry con typemod. Per ottenere il vecchio meccanismo con i vincoli spaziali si può settare la variabile use_typmod=false

For backwards compatibility and for spatial needs such as table inheritance where each child table may have different geometry type, the old check constraint behavior is still supported. If you need the old behavior, you need to pass in the new optional argument as false use_typmod=false. When this is done geometry columns will be created with no type modifiers but will have 3 constraints defined. In particular, this means that every geometry column belonging to a table has at least three constraints:

  • enforce_dims_the_geom - assicura che tutte le geometrie hanno la stessa dimensione (vedi ST_NDims)

  • enforce_geotype_the_geom - assicura che tutte le geometrie sono dello stesso tipo (vedi GeometryType)

  • enforce_srid_the_geom - - assicura che tutte le geometrie hanno la stessa proiezione (vedi ST_SRID)

Se alla funzione viene passato l' oid di una tabella, questa cerca di determinare srid, dimensione e tipo della geometria di tutte le colonne geometry della tabella, aggiungendo i vincoli se necessario. In caso di successo, una riga viene inserita nella tabella geometry_columns, altrimenti viene lanciata un'eccezione con un messaggio che descrive il problema.

Se alla funzione viene passato l'oid di una vista, questa cerca di determinare srid, dimensione e tipo della geometria di tutte le colonne geometry della vista, inserendo le appropriate righe nella tabella geometry_columns. I vincoli spaziali non vengono controllati né definiti.

La variante senza parametri è un semplice wrapper per la variante parametrizzata, che prima svuota e poi riempie la tabella geometry_columns per ogni vista e tabella spaziale nel database, aggiungendo gli appropriate vincoli spaziali. La funzione ritorna un sommario con il numero delle colonne geometry trovate e di quelle inserite in geometry_columns. La versione parametrizzata ritorna semplicemente il numero di righe inserite nella tabella geometry_columns.

Disponibilità: 1.4.0

Cambiamento nella versione 2.0.0: Per default la funzione utilizza ora type modifier invece di controllare i vincoli spaziali. il meccanismo con i vincoli può essere comunque attivato passando il parametro use_typmod e settandolo come false.

Miglioramento nelle version 2.0.0: Il parametro opzionale use_typmod è stato introdotto per permettere di controllare se le colonne devono essere create con typmodifier oppure con i vincoli spaziali.

Esempi

CREATE TABLE public.myspatial_table(gid serial, geom geometry);
INSERT INTO myspatial_table(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
-- Il comando seguente usa typ modifiers.  Per poter funzionare devono essere presenti dati nella tabella.
SELECT Populate_Geometry_Columns('public.myspatial_table'::regclass);

populate_geometry_columns
--------------------------
                        1
                        
                        
\d myspatial_table

                                   Table "public.myspatial_table"
 Column |           Type            |                           Modifiers                           
--------+---------------------------+---------------------------------------------------------------
 gid    | integer                   | not null default nextval('myspatial_table_gid_seq'::regclass)
 geom   | geometry(LineString,4326) |
-- Il comando seguente modificherà le colonne geometry usando i vincoli spaziali se non sono state definite con typmod oppure non hanno già i vincoli spaziali.
--Per poter funzionare devono essere presenti dati nella tabella.
CREATE TABLE public.myspatial_table_cs(gid serial, geom geometry);
INSERT INTO myspatial_table_cs(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
SELECT Populate_Geometry_Columns('public.myspatial_table_cs'::regclass, false);
populate_geometry_columns
--------------------------
                        1
\d myspatial_table_cs

                          Table "public.myspatial_table_cs"
 Column |   Type   |                            Modifiers                             
--------+----------+------------------------------------------------------------------
 gid    | integer  | not null default nextval('myspatial_table_cs_gid_seq'::regclass)
 geom   | geometry | 
Check constraints:
    "enforce_dims_geom" CHECK (st_ndims(geom) = 2)
    "enforce_geotype_geom" CHECK (geometrytype(geom) = 'LINESTRING'::text OR geom IS NULL)
    "enforce_srid_geom" CHECK (st_srid(geom) = 4326)

Name

UpdateGeometrySRID — Updates the SRID of all features in a geometry column, and the table metadata.

Synopsis

text UpdateGeometrySRID(varchar table_name, varchar column_name, integer srid);

text UpdateGeometrySRID(varchar schema_name, varchar table_name, varchar column_name, integer srid);

text UpdateGeometrySRID(varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integer srid);

Descrizione

Aggiorna lo SRID di tutti i record in una colonna geometry, aggiornando anche geometry_columns e il vincolo SRID della colonna. Usa la funzione current_schema() se lo schema non è passato come argomento.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

Insert geometries into roads table with a SRID set already using EWKT format:

COPY roads (geom) FROM STDIN;
SRID=4326;LINESTRING(0 0, 10 10)
SRID=4326;LINESTRING(10 10, 15 0)
\.
                

This will change the srid of the roads table to 4326 from whatever it was before:

SELECT UpdateGeometrySRID('roads','geom',4326);

The prior example is equivalent to this DDL statement:

ALTER TABLE roads
  ALTER COLUMN geom TYPE geometry(MULTILINESTRING, 4326)
    USING ST_SetSRID(geom,4326);

If you got the projection wrong (or brought it in as unknown) in load and you wanted to transform to web mercator all in one shot you can do this with DDL but there is no equivalent PostGIS management function to do so in one go.

ALTER TABLE roads
 ALTER COLUMN geom TYPE geometry(MULTILINESTRING, 3857) USING ST_Transform(ST_SetSRID(geom,4326),3857) ;

8.3. Costruttori geometrici.

ST_GeomCollFromText — Creates a GeometryCollection or Multi* geometry from a set of geometries.
ST_LineFromMultiPoint — Crea una LineString da una geometria MultiPoint.
ST_MakeEnvelope — Creates a rectangular Polygon from minimum and maximum coordinates.
ST_MakeLine

Crea una LineString da una geometria MultiPoint.

ST_MakePoint — Creates a 2D, 3DZ or 4D Point.
ST_MakePointM — Creates a Point from X, Y and M values.
ST_MakePolygon — Creates a Polygon from a shell and optional list of holes.
ST_Point — Creates a Point with the given coordinate values. Alias for ST_MakePoint.
ST_Polygon — Creates a Polygon from a LineString with a specified SRID.
ST_MakeEnvelope — Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system.
ST_HexagonGrid — Returns a set of hexagons and cell indices that completely cover the bounds of the geometry argument.
ST_Hexagon — Returns a single hexagon, using the provided edge size and cell coordinate within the hexagon grid space.
ST_SquareGrid — Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument.
ST_Square — Returns a single square, using the provided edge size and cell coordinate within the square grid space.

Name

ST_GeomCollFromText — Creates a GeometryCollection or Multi* geometry from a set of geometries.

Synopsis

geometry ST_MakeLine(geometry set geoms);

geometry ST_MakeLine(geometry geom1, geometry geom2);

geometry ST_MakeLine(geometry[] geoms_array);

Descrizione

Collects geometries into a geometry collection. The result is either a Multi* or a GeometryCollection, depending on whether the input geometries have the same or different types (homogeneous or heterogeneous). The input geometries are left unchanged within the collection.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries.

[Note]

If any of the input geometries are collections (Multi* or GeometryCollection) ST_Collect returns a GeometryCollection (since that is the only type which can contain nested collections). To prevent this, use ST_Dump in a subquery to expand the input collections to their atomic elements (see example below).

[Note]

ST_Collect and ST_Union appear similar, but in fact operate quite differently. ST_Collect aggregates geometries into a collection without changing them in any way. ST_Union geometrically merges geometries where they overlap, and splits linestrings at intersections. It may return single geometries when it dissolves boundaries.

Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi - uso di XLink

Collect 2D points.

SELECT ST_AsText( ST_Collect( ST_GeomFromText('POINT(1 2)'),
        ST_GeomFromText('POINT(-2 3)') ));

st_astext
----------
MULTIPOINT(1 2,-2 3)

Collect 3D points.

SELECT ST_AsEWKT( ST_Collect( ST_GeomFromEWKT('POINT(1 2 3)'),
                ST_GeomFromEWKT('POINT(1 2 4)') ) );

                st_asewkt
-------------------------
 MULTIPOINT(1 2 3,1 2 4)
 

Collect curves.

SELECT ST_AsText( ST_Collect( 'CIRCULARSTRING(220268 150415,220227 150505,220227 150406)',
                'CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));

                st_astext
------------------------------------------------------------------------------------
MULTICURVE(CIRCULARSTRING(220268 150415,220227 150505,220227 150406),
 CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))

Esempi - superficie poliedrica

Using an array constructor for a subquery.

SELECT ST_Collect( ARRAY( SELECT the_geom FROM sometable ) );

Using an array constructor for values.

SELECT ST_AsText(  ST_Collect(
                ARRAY[ ST_GeomFromText('LINESTRING(1 2, 3 4)'),
                        ST_GeomFromText('LINESTRING(3 4, 4 5)') ] )) As wktcollect;

--wkt collect --
MULTILINESTRING((1 2,3 4),(3 4,4 5))

Examples - Aggregate variant

Creating multiple collections by grouping geometries in a table.

SELECT stusps, ST_Collect(f.the_geom) as geom
         FROM (SELECT stusps, (ST_Dump(the_geom)).geom As the_geom
                                FROM
                                somestatetable ) As f
        GROUP BY stusps

Vedi anche

ST_Dump, ST_AsBinary


Name

ST_LineFromMultiPoint — Crea una LineString da una geometria MultiPoint.

Synopsis

geometry ST_LineFromMultiPoint(geometry aMultiPoint);

Descrizione

Crea una LineString da una geometria MultiPoint.

Use ST_MakeLine to create lines from Point or LineString inputs.

This function supports 3d and will not drop the z-index.

Esempi

Crea una LineString da una geometria MultiPoint.

--Crea una  3d line string da un 3d multipoint
SELECT ST_AsEWKT(ST_LineFromMultiPoint(ST_GeomFromEWKT('MULTIPOINT(1 2 3, 4 5 6, 7 8 9)')));
--result--
LINESTRING(1 2 3,4 5 6,7 8 9)

Vedi anche

ST_AsEWKT, ST_AsKML


Name

ST_MakeEnvelope — Creates a rectangular Polygon from minimum and maximum coordinates.

Synopsis

geometry ST_MakeEnvelope(double precision xmin, double precision ymin, double precision xmax, double precision ymax, integer srid=unknown);

Descrizione

Creates a rectangular Polygon from the minimum and maximum values for X and Y. Input values must be in the spatial reference system specified by the SRID. If no SRID is specified the unknown spatial reference system (SRID 0) is used.

Disponibilità: dalla versione 1.5.

Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.

Example: Building a bounding box polygon

SELECT ST_AsText(ST_MakeEnvelope(10, 10, 11, 11, 4326));

st_asewkt
-----------
POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))

Name

ST_MakeLine —

Crea una LineString da una geometria MultiPoint.

Synopsis

geometry ST_MakeLine(geometry set geoms);

geometry ST_MakeLine(geometry geom1, geometry geom2);

geometry ST_MakeLine(geometry[] geoms_array);

Descrizione

Creates a LineString containing the points of Point, MultiPoint, or LineString geometries. Other geometry types cause an error.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries. To ensure the order of the input geometries use ORDER BY in the function call, or a subquery with an ORDER BY clause.

Repeated nodes at the beginning of input LineStrings are collapsed to a single point. Repeated points in Point and MultiPoint inputs are not collapsed. ST_RemovePoint can be used to collapse repeated points from the output LineString.

This function supports 3d and will not drop the z-index.

Availability: 2.3.0 - Support for multipoint input elements was introduced

Availability: 2.0.0 - Support for linestring input elements was introduced

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

Examples: Two-input variant

Create a line composed of two points.

SELECT ST_MakeLine(ARRAY(SELECT ST_Centroid(the_geom) FROM visit_locations ORDER BY visit_time));

--Making a 3d line with 3 3-d points
SELECT ST_AsEWKT(ST_MakeLine(ARRAY[ST_MakePoint(1,2,3),
                                ST_MakePoint(3,4,5), ST_MakePoint(6,6,6)]));
                st_asewkt
-------------------------
LINESTRING(1 2 3,3 4 5,6 6 6)

Crea una BOX3D definita dalle geometrie dei punti 3d dati.

SELECT ST_AsEWKT( ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5) ));

                st_asewkt
-------------------------
 LINESTRING(1 2 3,3 4 5)

Create a line from two disjoint LineStrings.

select ST_AsText( ST_MakeLine( 'LINESTRING(0 0, 1 1)', 'LINESTRING(2 2, 3 3)' ) );

          st_astext
-----------------------------
 LINESTRING(0 0,1 1,2 2,3 3)

Examples: Array variant

Create a line from an array formed by a subquery with ordering.

SELECT ST_MakeLine( ARRAY( SELECT ST_Centroid(the_geom) FROM visit_locations ORDER BY visit_time) );

Create a 3D line from an array of 3D points

SELECT ST_MakeLine(ARRAY(SELECT ST_Centroid(the_geom) FROM visit_locations ORDER BY visit_time));

--Making a 3d line with 3 3-d points
SELECT ST_AsEWKT(ST_MakeLine(ARRAY[ST_MakePoint(1,2,3),
                                ST_MakePoint(3,4,5), ST_MakePoint(6,6,6)]));
                st_asewkt
-------------------------
LINESTRING(1 2 3,3 4 5,6 6 6)

Examples: Aggregate variant

This example queries time-based sequences of GPS points from a set of tracks and creates one record for each track. The result geometries are LineStrings composed of the GPS track points in the order of travel.

Using aggregate ORDER BY provides a correctly-ordered linestring.

SELECT gps.track_id, ST_MakeLine(gps.geom ORDER BY gps_time) As geom
        FROM gps_points As gps
        GROUP BY track_id;

Prior to PostgreSQL 9, ordering in a subquery can be used. However, sometimes the query plan may not respect the order of the subquery.

SELECT gps.track_id, ST_MakeLine(gps.geom) As geom
        FROM ( SELECT track_id, gps_time, geom
                        FROM gps_points ORDER BY track_id, gps_time ) As gps
        GROUP BY track_id;

Name

ST_MakePoint — Creates a 2D, 3DZ or 4D Point.

Synopsis

geometry ST_Point(float x_lon, float y_lat);

geometry ST_MakePointM(float x, float y, float m);

geometry ST_MakePoint(double precision x, double precision y, double precision z, double precision m);

Descrizione

Crea una BOX2D definita dalle geometrie dei punti dati.

Use ST_MakePointM to make points with XYM coordinates.

While not OGC-compliant, ST_MakePoint is faster and more precise than ST_GeomFromText and ST_PointFromText. It is also easier to use for numeric coordinate values.

[Note]

For geodetic coordinates, X is longitude and Y is latitude

This function supports 3d and will not drop the z-index.

Esempi

--Return point with unknown SRID
SELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

--Return point marked as WGS 84 long lat
SELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

--Return a 3D point (e.g. has altitude)
SELECT ST_MakePoint(1, 2,1.5);

--Get z of point
SELECT ST_Z(ST_MakePoint(1, 2,1.5));
result
-------
1.5

Name

ST_MakePointM — Creates a Point from X, Y and M values.

Synopsis

geometry ST_MakePointM(float x, float y, float m);

Descrizione

Creates a point with X, Y and M (measure) coordinates.

Use ST_MakePoint to make points with XY, XYZ, or XYZM coordinates.

[Note]

For geodetic coordinates, X is longitude and Y is latitude

Esempi

[Note]

ST_AsEWKT is used for text output because ST_AsText does not support M values.

Create point with unknown SRID.

SELECT ST_AsEWKT(  ST_MakePointM(-71.1043443253471, 42.3150676015829, 10)  );

                                   st_asewkt
-----------------------------------------------
 POINTM(-71.1043443253471 42.3150676015829 10)

Create point with a measure in the WGS 84 geodetic coordinate system.

SELECT ST_AsEWKT( ST_SetSRID(  ST_MakePointM(-71.104, 42.315, 10),  4326));

                                                st_asewkt
---------------------------------------------------------
SRID=4326;POINTM(-71.104 42.315 10)

Get measure of created point.

SELECT ST_M(  ST_MakePointM(-71.104, 42.315, 10)  );

result
-------
10

Name

ST_MakePolygon — Creates a Polygon from a shell and optional list of holes.

Synopsis

geometry ST_MakePolygon(geometry linestring);

geometry ST_MakePolygon(geometry outerlinestring, geometry[] interiorlinestrings);

Descrizione

Creates a Polygon formed by the given shell and optional array of holes. Input geometries must be closed LineStrings (rings).

Variant 1: Accepts one shell LineString.

Variant 2: Accepts a shell LineString and an array of inner (hole) LineStrings. A geometry array can be constructed using the PostgreSQL array_agg(), ARRAY[] or ARRAY() constructs.

[Note]

This function does not accept MultiLineStrings. Use ST_LineToCurve to generate a LineString, or ST_Dump to extract LineStrings.

This function supports 3d and will not drop the z-index.

Examples: Single input variant

Create a Polygon from a 2D LineString.

SELECT ST_MLineFromText('MULTILINESTRING((1 2, 3 4), (4 5, 6 7))');

Create a Polygon from an open LineString, using ST_StartPoint and ST_AddPoint to close it.

SELECT ST_MakePolygon( ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)) )
FROM (
  SELECT ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)') As open_line) As foo;

Create a Polygon from a 3D LineString

SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'));

st_asewkt
-----------
POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

Create a Polygon from a LineString with measures

SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)' ));

st_asewkt
----------
POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))

Examples: Outer shell with inner holes variant

Create a donut Polygon with an extra hole

SELECT ST_MakePolygon(
                ST_ExteriorRing(ST_Buffer(foo.line,10)),
        ARRAY[ST_Translate(foo.line,1,1),
                ST_ExteriorRing(ST_Buffer(ST_MakePoint(20,20),1)) ]
        )
FROM
        (SELECT ST_ExteriorRing(ST_Buffer(ST_MakePoint(10,10),10,10))
                As line )
                As foo;

Create a set of province boundaries with holes representing lakes. The input is a table of province Polygons/MultiPolygons and a table of water linestrings. Lines forming lakes are determined by using ST_IsClosed. The province linework is extracted by using ST_Boundary. As required by ST_MakePolygon, the boundary is forced to be a single LineString by using ST_LineToCurve. (However, note that if a province has more than one region or has islands this will produce an invallid polygon.) Using a LEFT JOIN ensures all provinces are included even if they have no lakes.

[Note]

The CASE construct is used because passing a null array into ST_MakePolygon results in a NULL return value.

SELECT p.gid, p.province_name,
        CASE WHEN array_agg(w.geom) IS NULL
        THEN p.geom
        ELSE  ST_MakePolygon( ST_LineMerge(ST_Boundary(p.geom)),
                        array_agg(w.geom)) END
FROM
        provinces p LEFT JOIN waterlines w
                ON (ST_Within(w.geom, p.geom) AND ST_IsClosed(w.geom))
GROUP BY p.gid, p.province_name, p.geom;

Another technique is to utilize a correlated subquery and the ARRAY() constructor that converts a row set to an array.

SELECT p.gid, p.province_name,
                CASE WHEN
                        ST_Accum(w.the_geom) IS NULL THEN p.the_geom
                ELSE  ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)), ST_Accum(w.the_geom)) END
        FROM
                provinces p LEFT JOIN waterlines w
                        ON (ST_Within(w.the_geom, p.the_geom) AND ST_IsClosed(w.the_geom))
        GROUP BY p.gid, p.province_name, p.the_geom;

        -- Stesso esempio di cui sopra, ma con una sottoquery correlata
        -- e la funzione PostgreSQL ARRAY() che converte il set di record in un vettore

        SELECT p.gid,  p.province_name, CASE WHEN
                EXISTS(SELECT w.the_geom
                        FROM waterlines w
                        WHERE ST_Within(w.the_geom, p.the_geom)
                        AND ST_IsClosed(w.the_geom))
                THEN
                ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)),
                        ARRAY(SELECT w.the_geom
                                FROM waterlines w
                                WHERE ST_Within(w.the_geom, p.the_geom)
                                AND ST_IsClosed(w.the_geom)))
                ELSE p.the_geom END As the_geom
        FROM
                provinces p;

Name

ST_Point — Creates a Point with the given coordinate values. Alias for ST_MakePoint.

Synopsis

geometry ST_Point(float x_lon, float y_lat);

Descrizione

Returns an Point with the given X and Y coordinate values. This is the SQL-MM alias for ST_MakePoint that takes just X and Y.

[Note]

For geodetic coordinates, X is longitude and Y is latitude

This method implements the SQL/MM specification. SQL-MM 3: 6.1.2

Examples: Geometry

SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)

Examples: Geography

SELECT CAST(ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326) As geography);

PostgreSQL also provides the :: short-hand for casting

SELECT CAST(ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326) As geography);

If the point coordinates are not in a geodetic coordinate system (such as WGS84), then they must be reprojected before casting to a geography. In this example a point in Pennsylvania State Plane feet (SRID 2273) is projected to WGS84 (SRID 4326).

SELECT CAST(ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326) As geography);

Name

ST_Polygon — Creates a Polygon from a LineString with a specified SRID.

Synopsis

geometry ST_Polygon(geometry aLineString, integer srid);

Descrizione

Returns a polygon built from the given LineString and sets the spatial reference system from the srid.

ST_Polygon is similar to ST_MakePolygon Variant 1 with the addition of setting the SRID.

, ST_MakePoint, ST_SetSRID

[Note]

This function does not accept MultiLineStrings. Use ST_LineToCurve to generate a LineString, or ST_Dump to extract LineStrings.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.3.2

This function supports 3d and will not drop the z-index.

Esempi

Create a 2D polygon.

SELECT ST_AsText( ST_Polygon('LINESTRING(75 29, 77 29, 77 29, 75 29)'::geometry, 4326) );

-- result --
POLYGON((75 29, 77 29, 77 29, 75 29))

Create a 3D polygon.

SELECT ST_AsEWKT( ST_Polygon( ST_GeomFromEWKT('LINESTRING(75 29 1, 77 29 2, 77 29 3, 75 29 1)'), 4326) );

-- result --
SRID=4326;POLYGON((75 29 1, 77 29 2, 77 29 3, 75 29 1))

Name

ST_MakeEnvelope — Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system.

Synopsis

geometry ST_MakePoint(double precision x, double precision y, double precision z, double precision m);

Descrizione

Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system. By default, the bounds are the in EPSG:3857 using the standard range of the Web Mercator system (-20037508.342789, 20037508.342789). The optional bounds parameter can be used to generate envelopes for any tiling scheme: provide a geometry that has the SRID and extent of the initial "zoom level zero" square within which the tile system is to be inscribed.

The optional margin parameter can be used to grow a tile by the given percentage, e.g. margin=0.125 grows the tile by 12.5%, which is equivalent to buffer=512 when extent is 4096, as used in ST_AsSVG. This is useful to create a tile buffer -- to include data lying outside of the tile's visible area, but whose existence affects current tile's rendering. For example, a city name (a geopoint) could be near an edge of a tile, but the text would need to render on two tiles, even though the geopoint is located in the visible area of just one tile. Using an expanded tile in a search would include the city geopoint for both tiles. Use negative value to shrink the tile instead. Values less than -0.5 are prohibited because that would eliminate the tile completely. Do not use margin with ST_AsMVTGeom(). See example in ST_AsGML.

Miglioramento nella versione: 2.0.0 introdotto opzionale parametro SRID.

Disponibilità: dalla versione 1.5.

Example: Building a tile envelope

SELECT ST_AsText( ST_TileEnvelope(2, 1, 1) );

 st_astext
------------------------------
 POLYGON((-10018754.1713945 0,-10018754.1713945 10018754.1713945,0 10018754.1713945,0 0,-10018754.1713945 0))

SELECT ST_AsText( ST_TileEnvelope(3, 1, 1, ST_MakeEnvelope(-180, -90, 180, 90, 4326) ) );

                      st_astext
------------------------------------------------------
 POLYGON((-135 45,-135 67.5,-90 67.5,-90 45,-135 45))

Vedi anche

ST_MakeEnvelope


Name

ST_HexagonGrid — Returns a set of hexagons and cell indices that completely cover the bounds of the geometry argument.

Synopsis

geometry ST_Point(float x_lon, float y_lat);

Descrizione

Starts with the concept of a hexagon tiling of the plane. (Not a hexagon tiling of the globe, this is not the H3 tiling scheme.) For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique hexagonal tiling of the plane, Tiling(SRS, Size). This function answers the question: what hexagons in a given Tiling(SRS, Size) overlap with a given bounds.

The SRS for the output hexagons is the SRS provided by the bounds geometry.

Doubling or tripling the edge size of the hexagon generates a new parent tiling that fits with the origin tiling. Unfortunately, it is not possible to generate parent hexagon tilings that the child tiles perfectly fit inside.

Disponibilità: dalla versione 1.5.

Example: Counting points in hexagons

To do a point summary against a hexagonal tiling, generate a hexagon grid using the extent of the points as the bounds, then spatially join to that grid.

SELECT COUNT(*), hexes.geom
FROM
    ST_HexagonGrid(
        10000,
        ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
    ) AS hexes
    INNER JOIN
    pointtable AS pts
    ON ST_Intersects(pts.geom, hexes.geom)
GROUP BY hexes.geom;

Example: Generating hex coverage of polygons

If we generate a set of hexagons for each polygon boundary and filter out those that do not intersect their hexagons, we end up with a tiling for each polygon.

Tiling states results in a hexagon coverage of each state, and multiple hexagons overlapping at the borders between states.

[Note]

The LATERAL keyword is implied for set-returning functions when referring to a prior table in the FROM list. So CROSS JOIN LATERAL, CROSS JOIN, or just plain , are equivalent constructs for this example.

SELECT admin1.gid, hex.geom
FROM
    admin1
    CROSS JOIN
    ST_HexagonGrid(100000, admin1.geom) AS hex
WHERE
    adm0_a3 = 'USA'
    AND
    ST_Intersects(admin1.geom, hex.geom)

Name

ST_Hexagon — Returns a single hexagon, using the provided edge size and cell coordinate within the hexagon grid space.

Synopsis

geometry ST_MakePoint(double precision x, double precision y, double precision z, double precision m);

Descrizione

Uses the same hexagon tiling concept as ST_HexagonGrid, but generates just one hexagon at the desired cell coordinate. Optionally, can adjust origin coordinate of the tiling, the default origin is at 0,0.

Hexagons are generated with no SRID set, so use ST_SetSRID to set the SRID to the one you expect.

Disponibilità: dalla versione 1.5.

Example: Creating a hexagon at the origin

SELECT ST_AsText(ST_SetSRID(ST_Hexagon(1.0, 0, 0), 3857));

POLYGON((-1 0,-0.5
         -0.866025403784439,0.5
         -0.866025403784439,1
         0,0.5
         0.866025403784439,-0.5
         0.866025403784439,-1 0)) 

Name

ST_SquareGrid — Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument.

Synopsis

geometry ST_Point(float x_lon, float y_lat);

Descrizione

Starts with the concept of a square tiling of the plane. For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique square tiling of the plane, Tiling(SRS, Size). This function answers the question: what grids in a given Tiling(SRS, Size) overlap with a given bounds.

The SRS for the output squares is the SRS provided by the bounds geometry.

Doubling or edge size of the square generates a new parent tiling that perfectly fits with the original tiling. Standard web map tilings in mercator are just powers-of-two square grids in the mercator plane.

Disponibilità: dalla versione 1.5.

Example: Generating a 1 degree grid for a country

The grid will fill the whole bounds of the country, so if you want just squares that touch the country you will have to filter afterwards with ST_Intersects.

WITH grid AS (
SELECT (ST_SquareGrid(1, ST_Transform(geom,4326))).*
FROM admin0 WHERE name = 'Canada'
)
  SELEcT ST_AsText(geom)
  FROM grid

Example: Counting points in squares (using single chopped grid)

To do a point summary against a square tiling, generate a square grid using the extent of the points as the bounds, then spatially join to that grid. Note the estimated extent might be off from actual extent, so be cautious and at very least make sure you've analyzed your table.

SELECT COUNT(*), squares.geom
    FROM
    pointtable AS pts
    INNER JOIN
    ST_SquareGrid(
        1000,
        ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
    ) AS squares
    ON ST_Intersects(pts.geom, squares.geom)
    GROUP BY squares.geom

Example: Counting points in squares using set of grid per point

This yields the same result as the first example but will be slower for a large number of points

SELECT COUNT(*), squares.geom
    FROM
    pointtable AS pts
    INNER JOIN
    ST_SquareGrid(
        1000,
       pts.geom
    ) AS squares
    ON ST_Intersects(pts.geom, squares.geom)
    GROUP BY squares.geom

Name

ST_Square — Returns a single square, using the provided edge size and cell coordinate within the square grid space.

Synopsis

geometry ST_MakePoint(double precision x, double precision y, double precision z, double precision m);

Descrizione

Uses the same square tiling concept as ST_SquareGrid, but generates just one square at the desired cell coordinate. Optionally, can adjust origin coordinate of the tiling, the default origin is at 0,0.

Squares are generated with no SRID set, so use ST_SetSRID to set the SRID to the one you expect.

Disponibilità: dalla versione 1.5.

Example: Creating a square at the origin

SELECT ST_AsText(ST_MakeEnvelope(10, 10, 11, 11, 4326));

st_asewkt
-----------
POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))

8.4. Geometry Accessors

GeometryType — Restituisce il tipo di geometria per il valore ST_Geometry.
ST_Boundary — Restituisce il tipo di geometria per il valore ST_Geometry.
ST_BoundingDiagonal — Returns the diagonal of a geometry's bounding box.
ST_CoordDim

Restituisce la dimensione delle coordinate di ST_Geometry value.

ST_Dimension

Restituisce la dimensione delle coordinate di ST_Geometry value.

ST_Dump — Returns a set of geometry_dump rows for the components of a geometry.
ST_NumPoints — Returns a set of geometry_dump rows for the coordinates in a geometry.
ST_NumPoints — Returns a set of geometry_dump rows for the segments in a geometry.
ST_NRings — Returns a set of geometry_dump rows for the exterior and interior rings of a Polygon.
ST_EndPoint — Returns the last point of a LineString or CircularLineString.
ST_Envelope — Returns a geometry representing the bounding box of a geometry.
ST_ExteriorRing — Returns a LineString representing the exterior ring of a Polygon.
ST_GeometryN — Restituisce il tipo di geometria per il valore ST_Geometry.
ST_GeometryType — Restituisce il tipo di geometria per il valore ST_Geometry.
ST_HasArc — Tests if a geometry contains a circular arc
ST_InteriorRingN — Returns the Nth interior ring (hole) of a Polygon.
ST_IsClosed — Restituisce TRUE se il punto iniziale e quello finale di LINESTRING coincidono. Per le superfici poliedriche indica una superficie chiusa (volumetrica).
ST_IsCollection — Restituisce TRUE se la geometria è una geometrycollection, un poligono o un punto vuoto, ecc.
ST_IsEmpty — Tests if a geometry is empty.
ST_IsPolygonCCW — Tests if Polygons have exterior rings oriented counter-clockwise and interior rings oriented clockwise.
ST_IsPolygonCW — Tests if Polygons have exterior rings oriented clockwise and interior rings oriented counter-clockwise.
ST_IsRing — Tests if a LineString is closed and simple.
ST_IsSimple — Tests if a geometry has no points of self-intersection or self-tangency.
ST_M — Returns the M coordinate of a Point.
ST_MemSize — Restituisce il tipo di geometria per il valore ST_Geometry.
ST_NDims

Restituisce la dimensione delle coordinate di ST_Geometry value.

ST_NPoints — Returns the number of points (vertices) in a geometry.
ST_NRings — Returns the number of rings in a polygonal geometry.
ST_NumGeometries — Restituisce TRUE se la geometria è una geometrycollection, un poligono o un punto vuoto, ecc.
ST_NumInteriorRings — Returns the number of interior rings (holes) of a Polygon.
ST_NumInteriorRing — Returns the number of interior rings (holes) of a Polygon. Aias for ST_NumInteriorRings
ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
ST_NumPoints — Returns the number of points in a LineString or CircularString.
ST_PatchN — Restituisce il tipo di geometria per il valore ST_Geometry.
ST_PointN — Returns the Nth point in the first LineString or circular LineString in a geometry.
ST_Points

Restituisce la dimensione delle coordinate di ST_Geometry value.

ST_StartPoint — Returns the first point of a LineString.
ST_Summary — Returns a text summary of the contents of a geometry.
ST_X — Returns the X coordinate of a Point.
ST_Y — Returns the Y coordinate of a Point.
ST_Z — Returns the Z coordinate of a Point.
ST_Zmflag — Restituisce la dimensione delle coordinate di ST_Geometry value.

Name

GeometryType — Restituisce il tipo di geometria per il valore ST_Geometry.

Synopsis

text GeometryType(geometry geomA);

Descrizione

Restituisce il tipo di geometria come stringa. Per esempio: 'LINESTRING', 'POLYGON', 'MULTIPOINT', ecc.

OGC SPEC s2.1.1.1 - Returns the name of the instantiable subtype of Geometry of which this Geometry instance is a member. The name of the instantiable subtype of Geometry is returned as a string.

[Note]

Questa funzione indica anche se la geometria viene misurata, restituendo una stringa nella forma 'POINTM'.

Migliorato: Nella 2.0.0 è stato introdotto il supporto per le superfici poliedriche, i triangoli e i TIN.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

SELECT GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
 geometrytype
--------------
 LINESTRING
SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
                        --result
                        POLYHEDRALSURFACE
                        
SELECT GeometryType(geom) as result
  FROM
    (SELECT
       ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )')  AS geom
    ) AS g;
 result
--------
 TIN    

Si veda anche

ST_GeometryType


Name

ST_Boundary — Restituisce il tipo di geometria per il valore ST_Geometry.

Synopsis

geometry ST_Boundary(geometry geomA);

Descrizione

Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described in section 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resulting boundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.

Eseguito dal modulo GEOS

[Note]

Prma della 2.0.0, questa funzione dava un'eccezione se usata con GEOMETRYCOLLECTION. A partire dalla 2.0.0 in poi, restituirà invece NULL (input non supportato).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. OGC SPEC s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.14

This function supports 3d and will not drop the z-index.

Enhanced: 2.1.0 support for Triangle was introduced

Changed: 3.2.0 support for TIN, does not use geos, does not linearize curves

Esempi

Linestring with boundary points overlaid

SELECT ST_Boundary(geom)
FROM (SELECT 'LINESTRING(100 150,50 60, 70 80, 160 170)'::geometry As geom) As f;
                                

-- ST_AsText output
MULTIPOINT(100 150,160 170)

polygon holes with boundary multilinestring

SELECT ST_Boundary(geom)
FROM (SELECT
'POLYGON (( 10 130, 50 190, 110 190, 140 150, 150 80, 100 10, 20 40, 10 130 ),
        ( 70 40, 100 50, 120 80, 80 110, 50 90, 70 40 ))'::geometry As geom) As f;
                                

-- ST_AsText output
MULTILINESTRING((10 130,50 190,110 190,140 150,150 80,100 10,20 40,10 130),
        (70 40,100 50,120 80,80 110,50 90,70 40))

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(1 1,0 0, -1 1)')));
st_astext
-----------
MULTIPOINT(1 1,-1 1)

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))')));
st_astext
----------
LINESTRING(1 1,0 0,-1 1,1 1)

--Usando un poligono 3d
SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))')));

st_asewkt
-----------------------------------
LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)

--Usando una multilinestring 3d
SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )')));

st_asewkt
----------
MULTIPOINT(-1 1 1,1 1 0.75)

Name

ST_BoundingDiagonal — Returns the diagonal of a geometry's bounding box.

Synopsis

geometry ST_BoundingDiagonal(geometry geom, boolean fits=false);

Descrizione

Returns the diagonal of the supplied geometry's bounding box as a LineString. The diagonal is a 2-point LineString with the minimum values of each dimension in its start point and the maximum values in its end point. If the input geometry is empty, the diagonal line is a LINESTRING EMPTY.

The optional fits parameter specifies if the best fit is needed. If false, the diagonal of a somewhat larger bounding box can be accepted (which is faster to compute for geometries with many vertices). In either case, the bounding box of the returned diagonal line always covers the input geometry.

The returned geometry retains the SRID and dimensionality (Z and M presence) of the input geometry.

[Note]

In degenerate cases (i.e. a single vertex in input) the returned linestring will be formally invalid (no interior). The result is still topologically valid.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

Esempi

-- Get the minimum X in a buffer around a point
SELECT ST_X(ST_StartPoint(ST_BoundingDiagonal(
  ST_Buffer(ST_Point(0,0),10)
)));
 st_x
------
  -10
                

Name

ST_CoordDim —

Restituisce la dimensione delle coordinate di ST_Geometry value.

Synopsis

integer ST_CoordDim(geometry geomA);

Descrizione

Restituisce la dimensione delle coordinate di ST_Geometry value.

This is the MM compliant alias name for ST_NDims

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.3

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

SELECT ST_CoordDim('CIRCULARSTRING(1 2 3, 1 3 4, 5 6 7, 8 9 10, 11 12 13)');
                        ---result--
                                3

                                SELECT ST_CoordDim(ST_Point(1,2));
                        --result--
                                2

                

Si veda anche

ST_NDims


Name

ST_Dimension —

Restituisce la dimensione delle coordinate di ST_Geometry value.

Synopsis

integer ST_Dimension(geometry g);

Descrizione

La dimensione inerente a questo oggetto Geometry, che deve essere minore o uguale alla dimensione delle coordinate. La specifica OGC s2.1.1.1 restituisce 0 per POINT, 1 per LINESTRING, 2 per POLYGON, e la maggiore fra le dimensioni dei componenti di una GEOMETRYCOLLECTION. Se la geometria è sconosciuta (vuota), viene restituito il valore NULL.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.2

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le supefici poliedriche e i TIN. Non viene più generata un'eccezione se viene data una geometria vuota.

[Note]

Prima della 2.0.0, questa funzione dava un'eccezione se usata con una geometria vuota.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

SELECT ST_Dimension('GEOMETRYCOLLECTION(LINESTRING(1 1,0 0),POINT(0 0))');
ST_Dimension
-----------
1

Si veda anche

ST_NDims


Name

ST_Dump — Returns a set of geometry_dump rows for the components of a geometry.

Synopsis

geometry ST_Envelope(geometry g1);

Descrizione

A set-returning function (SRF) that extracts the components of a geometry. It returns a set of geometry_dump rows, each containing a geometry (geom field) and an array of integers (path field).

For an atomic geometry type (POINT,LINESTRING,POLYGON) a single record is returned with an empty path array and the input geometry as geom. For a collection or multi-geometry a record is returned for each of the collection components, and the path denotes the position of the component inside the collection.

ST_Dump is useful for expanding geometries. It is the inverse of a ST_GeomCollFromText / GROUP BY, in that it creates new rows. For example it can be use to expand MULTIPOLYGONS into POLYGONS.

Migliorato: Nella 2.0.0 è stato introdotto il supporto per le superfici poliedriche, i triangoli e i TIN.

Availability: PostGIS 1.0.0RC1. Requires PostgreSQL 7.3 or higher.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Esempi standard

SELECT sometable.field1, sometable.field1,
      (ST_Dump(sometable.the_geom)).geom AS the_geom
FROM sometable;

-- Break a compound curve into its constituent linestrings and circularstrings
SELECT ST_AsEWKT(a.geom), ST_HasArc(a.geom)
  FROM ( SELECT (ST_Dump(p_geom)).geom AS geom
         FROM (SELECT ST_GeomFromEWKT('COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))') AS p_geom) AS b
        ) AS a;
          st_asewkt          | st_hasarc
-----------------------------+----------
 CIRCULARSTRING(0 0,1 1,1 0) | t
 LINESTRING(1 0,0 1)         | f
(2 rows)

Esempi con superfici poliedriche, TIN e triangoli

-- Polyhedral surface example
-- Break a Polyhedral surface into its faces
SELECT (a.p_geom).path[1] As path, ST_AsEWKT((a.p_geom).geom) As geom_ewkt
  FROM (SELECT ST_Dump(ST_GeomFromEWKT('POLYHEDRALSURFACE(
((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),  ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),  ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
)') ) AS p_geom )  AS a;

 path |                geom_ewkt
------+------------------------------------------
    1 | POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0))
    2 | POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))
    3 | POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))
    4 | POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0))
    5 | POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0))
    6 | POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))
-- TIN --
SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
  FROM
    (SELECT
       ST_Dump( ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )') ) AS gdump
    ) AS g;
-- result --
 path |                 wkt
------+-------------------------------------
 {1}  | TRIANGLE((0 0 0,0 0 1,0 1 0,0 0 0))
 {2}  | TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

Name

ST_NumPoints — Returns a set of geometry_dump rows for the coordinates in a geometry.

Synopsis

geometry ST_StartPoint(geometry geomA);

Descrizione

A set-returning function (SRF) that extracts the coordinates (vertices) of a geometry. It returns a set of geometry_dump rows, each containing a geometry (geom field) and an array of integers (path field).

  • the geom field POINTs represent the coordinates of the supplied geometry.

  • the path field (an integer[]) is an index enumerating the coordinate positions in the elements of the supplied geometry. The indices are 1-based. For example, for a LINESTRING the paths are {i} where i is the nth coordinate in the LINESTRING. For a POLYGON the paths are {i,j} where i is the ring number (1 is outer; inner rings follow) and j is the coordinate position in the ring.

To obtain a single geometry containing the coordinates use ST_Points.

Enhanced: 2.1.0 Faster speed. Reimplemented as native-C.

Migliorato: Nella 2.0.0 è stato introdotto il supporto per le superfici poliedriche, i triangoli e i TIN.

Disponibilità: 2.0

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Classic Explode a Table of LineStrings into nodes

SELECT edge_id, (dp).path[1] As index, ST_AsText((dp).geom) As wktnode
FROM (SELECT 1 As edge_id
        , ST_DumpPoints(ST_GeomFromText('LINESTRING(1 2, 3 4, 10 10)')) AS dp
     UNION ALL
     SELECT 2 As edge_id
        , ST_DumpPoints(ST_GeomFromText('LINESTRING(3 5, 5 6, 9 10)')) AS dp
   ) As foo;
 edge_id | index |    wktnode
---------+-------+--------------
       1 |     1 | POINT(1 2)
       1 |     2 | POINT(3 4)
       1 |     3 | POINT(10 10)
       2 |     1 | POINT(3 5)
       2 |     2 | POINT(5 6)
       2 |     3 | POINT(9 10)

Esempi standard

SELECT path, ST_AsText(geom)
FROM (
  SELECT (ST_DumpPoints(g.geom)).*
  FROM
    (SELECT
       'GEOMETRYCOLLECTION(
          POINT ( 0 1 ),
          LINESTRING ( 0 3, 3 4 ),
          POLYGON (( 2 0, 2 3, 0 2, 2 0 )),
          POLYGON (( 3 0, 3 3, 6 3, 6 0, 3 0 ),
                   ( 5 1, 4 2, 5 2, 5 1 )),
          MULTIPOLYGON (
                  (( 0 5, 0 8, 4 8, 4 5, 0 5 ),
                   ( 1 6, 3 6, 2 7, 1 6 )),
                  (( 5 4, 5 8, 6 7, 5 4 ))
          )
        )'::geometry AS geom
    ) AS g
  ) j;

   path    | st_astext
-----------+------------
 {1,1}     | POINT(0 1)
 {2,1}     | POINT(0 3)
 {2,2}     | POINT(3 4)
 {3,1,1}   | POINT(2 0)
 {3,1,2}   | POINT(2 3)
 {3,1,3}   | POINT(0 2)
 {3,1,4}   | POINT(2 0)
 {4,1,1}   | POINT(3 0)
 {4,1,2}   | POINT(3 3)
 {4,1,3}   | POINT(6 3)
 {4,1,4}   | POINT(6 0)
 {4,1,5}   | POINT(3 0)
 {4,2,1}   | POINT(5 1)
 {4,2,2}   | POINT(4 2)
 {4,2,3}   | POINT(5 2)
 {4,2,4}   | POINT(5 1)
 {5,1,1,1} | POINT(0 5)
 {5,1,1,2} | POINT(0 8)
 {5,1,1,3} | POINT(4 8)
 {5,1,1,4} | POINT(4 5)
 {5,1,1,5} | POINT(0 5)
 {5,1,2,1} | POINT(1 6)
 {5,1,2,2} | POINT(3 6)
 {5,1,2,3} | POINT(2 7)
 {5,1,2,4} | POINT(1 6)
 {5,2,1,1} | POINT(5 4)
 {5,2,1,2} | POINT(5 8)
 {5,2,1,3} | POINT(6 7)
 {5,2,1,4} | POINT(5 4)
(29 rows)

Esempi con superfici poliedriche, TIN e triangoli

-- Polyhedral surface cube --
SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
  FROM
    (SELECT
       ST_DumpPoints(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )') ) AS gdump
    ) AS g;
-- result --
  path   |     wkt
---------+--------------
 {1,1,1} | POINT(0 0 0)
 {1,1,2} | POINT(0 0 1)
 {1,1,3} | POINT(0 1 1)
 {1,1,4} | POINT(0 1 0)
 {1,1,5} | POINT(0 0 0)
 {2,1,1} | POINT(0 0 0)
 {2,1,2} | POINT(0 1 0)
 {2,1,3} | POINT(1 1 0)
 {2,1,4} | POINT(1 0 0)
 {2,1,5} | POINT(0 0 0)
 {3,1,1} | POINT(0 0 0)
 {3,1,2} | POINT(1 0 0)
 {3,1,3} | POINT(1 0 1)
 {3,1,4} | POINT(0 0 1)
 {3,1,5} | POINT(0 0 0)
 {4,1,1} | POINT(1 1 0)
 {4,1,2} | POINT(1 1 1)
 {4,1,3} | POINT(1 0 1)
 {4,1,4} | POINT(1 0 0)
 {4,1,5} | POINT(1 1 0)
 {5,1,1} | POINT(0 1 0)
 {5,1,2} | POINT(0 1 1)
 {5,1,3} | POINT(1 1 1)
 {5,1,4} | POINT(1 1 0)
 {5,1,5} | POINT(0 1 0)
 {6,1,1} | POINT(0 0 1)
 {6,1,2} | POINT(1 0 1)
 {6,1,3} | POINT(1 1 1)
 {6,1,4} | POINT(0 1 1)
 {6,1,5} | POINT(0 0 1)
(30 rows)
-- Triangle --
SELECT (g.gdump).path, ST_AsText((g.gdump).geom) as wkt
  FROM
    (SELECT
       ST_DumpPoints( ST_GeomFromEWKT('TRIANGLE ((
                0 0,
                0 9,
                9 0,
                0 0
            ))') ) AS gdump
    ) AS g;
-- result --
 path |    wkt
------+------------
 {1}  | POINT(0 0)
 {2}  | POINT(0 9)
 {3}  | POINT(9 0)
 {4}  | POINT(0 0)
-- TIN --
SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
  FROM
    (SELECT
       ST_DumpPoints( ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )') ) AS gdump
    ) AS g;
-- result --
  path   |     wkt
---------+--------------
 {1,1,1} | POINT(0 0 0)
 {1,1,2} | POINT(0 0 1)
 {1,1,3} | POINT(0 1 0)
 {1,1,4} | POINT(0 0 0)
 {2,1,1} | POINT(0 0 0)
 {2,1,2} | POINT(0 1 0)
 {2,1,3} | POINT(1 1 0)
 {2,1,4} | POINT(0 0 0)
(8 rows)

Name

ST_NumPoints — Returns a set of geometry_dump rows for the segments in a geometry.

Synopsis

geometry ST_StartPoint(geometry geomA);

Descrizione

A set-returning function (SRF) that extracts the segments of a geometry. It returns a set of geometry_dump rows, each containing a geometry (geom field) and an array of integers (path field).

  • the geom field LINESTRINGs represent the segments of the supplied geometry.

  • the path field (an integer[]) is an index enumerating the segment start point positions in the elements of the supplied geometry. The indices are 1-based. For example, for a LINESTRING the paths are {i} where i is the nth segment start point in the LINESTRING. For a POLYGON the paths are {i,j} where i is the ring number (1 is outer; inner rings follow) and j is the segment start point position in the ring.

Disponibilità: 2.0

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Esempi standard

SELECT path, ST_AsText(geom)
FROM (
    SELECT (ST_DumpSegments(g.geom)).*
    FROM (SELECT 'GEOMETRYCOLLECTION(
    LINESTRING(1 1, 3 3, 4 4),
    POLYGON((5 5, 6 6, 7 7, 5 5))
)'::geometry AS geom
        ) AS g
) j;

  path   │      st_astext
---------------------------------
 {1,1}   │ LINESTRING(1 1,3 3)
 {1,2}   │ LINESTRING(3 3,4 4)
 {2,1,1} │ LINESTRING(5 5,6 6)
 {2,1,2} │ LINESTRING(6 6,7 7)
 {2,1,3} │ LINESTRING(7 7,5 5)
(5 rows)

Esempi con superfici poliedriche, TIN e triangoli

-- Triangle --
SELECT path, ST_AsText(geom)
FROM (
    SELECT (ST_DumpSegments(g.geom)).*
    FROM (SELECT 'TRIANGLE((
        0 0,
        0 9,
        9 0,
        0 0
    ))'::geometry AS geom
        ) AS g
) j;

 path  │      st_astext
 ---------------------------------
 {1,1} │ LINESTRING(0 0,0 9)
 {1,2} │ LINESTRING(0 9,9 0)
 {1,3} │ LINESTRING(9 0,0 0)
(3 rows)
-- TIN --
SELECT path, ST_AsEWKT(geom)
FROM (
    SELECT (ST_DumpSegments(g.geom)).*
    FROM (SELECT 'TIN(((
        0 0 0,
        0 0 1,
        0 1 0,
        0 0 0
    )), ((
        0 0 0,
        0 1 0,
        1 1 0,
        0 0 0
    ))
    )'::geometry AS geom
        ) AS g
) j;

  path   │        st_asewkt
  ---------------------------------
 {1,1,1} │ LINESTRING(0 0 0,0 0 1)
 {1,1,2} │ LINESTRING(0 0 1,0 1 0)
 {1,1,3} │ LINESTRING(0 1 0,0 0 0)
 {2,1,1} │ LINESTRING(0 0 0,0 1 0)
 {2,1,2} │ LINESTRING(0 1 0,1 1 0)
 {2,1,3} │ LINESTRING(1 1 0,0 0 0)
(6 rows)

Name

ST_NRings — Returns a set of geometry_dump rows for the exterior and interior rings of a Polygon.

Synopsis

geometry ST_ExteriorRing(geometry a_polygon);

Descrizione

A set-returning function (SRF) that extracts the rings of a polygon. It returns a set of geometry_dump rows, each containing a geometry (geom field) and an array of integers (path field).

The geom field contains each ring as a POLYGON. The path field is an integer array of length 1 containing the polygon ring index. The exterior ring (shell) has index 0. The interior rings (holes) have indices of 1 and higher.

[Note]

Non funzionerà per i MULTIPOLYGON. Da utilizzare assieme a ST_Dump per i MULTIPOLYGON

Availability: PostGIS 1.1.3. Requires PostgreSQL 7.3 or higher.

This function supports 3d and will not drop the z-index.

Esempi

General form of query.

SELECT polyTable.field1, polyTable.field1,
          (ST_DumpRings(polyTable.the_geom)).geom As the_geom
FROM polyTable;

A polygon with a single hole.

SELECT path, ST_AsEWKT(geom) As the_geom
        FROM ST_DumpRings(
                ST_GeomFromEWKT('POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 1,-8148958 5132508 1,-8148941 5132466 1,-8148924 5132394 1,
                -8148903 5132210 1,-8148930 5131967 1,-8148992 5131978 1,-8149237 5132093 1,-8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,
                -8150305 5132788 1,-8149064 5133092 1),
                (-8149362 5132394 1,-8149446 5132501 1,-8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))')
                )  as foo;
 path |                                            the_geom
----------------------------------------------------------------------------------------------------------------
  {0} | POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 1,-8148958 5132508 1,
          |          -8148941 5132466 1,-8148924 5132394 1,
          |          -8148903 5132210 1,-8148930 5131967 1,
          |          -8148992 5131978 1,-8149237 5132093 1,
          |          -8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,-8150305 5132788 1,-8149064 5133092 1))
  {1} | POLYGON((-8149362 5132394 1,-8149446 5132501 1,
          |          -8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))

Name

ST_EndPoint — Returns the last point of a LineString or CircularLineString.

Synopsis

geometry ST_Envelope(geometry g1);

Descrizione

Restituisce l'ultimo punto di una geometria LINESTRING come POINT o NULL se il parametro di input non è una LINESTRING.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.4

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Modifica: La versione 2.0.0 non funziona più con geometrie singole di stringhe multilinea. Nelle versioni precedenti di PostGIS una stringa multilinea con una sola linea avrebbe funzionato tranquillamente con questa funzione, restituendo il punto di inizio. Nella versione 2.0.0 la funzione restituisce NULL come per qualsiasi altra stringa multilinea. Il comportamento precedente non era documentato, ma le persone che presumevano di avere i dati memorizzati come LINESTRING potrebbero trovare che questi ora restituiscono il valore NULL.

Esempi

End point of a LineString

postgis=# SELECT ST_AsText(ST_EndPoint('LINESTRING(1 1, 2 2, 3 3)'::geometry));
 st_astext
------------
 POINT(3 3)

End point of a non-LineString is NULL

SELECT ST_EndPoint('POINT(1 1)'::geometry) IS NULL AS is_null;
  is_null
----------
 t

End point of a 3D LineString

--3d endpoint
SELECT ST_AsEWKT(ST_EndPoint('LINESTRING(1 1 2, 1 2 3, 0 0 5)'));
  st_asewkt
--------------
 POINT(0 0 5)

End point of a CircularString

SELECT ST_AsText(ST_EndPoint('CIRCULARSTRING(5 2,-3 1.999999, -2 1, -4 2, 6 3)'::geometry));
 st_astext
------------
 POINT(6 3)

Si veda anche

ST_PointN, ST_StartPoint


Name

ST_Envelope — Returns a geometry representing the bounding box of a geometry.

Synopsis

geometry ST_Envelope(geometry g1);

Descrizione

Returns the double-precision (float8) minimum bounding box for the supplied geometry, as a geometry. The polygon is defined by the corner points of the bounding box ((MINX, MINY), (MINX, MAXY), (MAXX, MAXY), (MAXX, MINY), (MINX, MINY)). (PostGIS will add a ZMIN/ZMAX coordinate as well).

I casi degeneri (linee verticali, punti) restituiranno una geometria di dimensione inferiore al POLYGON, cioè POINT o LINESTRING.

Disponibilità: il comportamento nella 1.5.0 è stato cambiato per dare in uscita numeri in precisione doppia anziche float4

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.15

Esempi

SELECT ST_AsText(ST_Envelope('POINT(1 3)'::geometry));
 st_astext
------------
 POINT(1 3)
(1 row)


SELECT ST_AsText(ST_Envelope('LINESTRING(0 0, 1 3)'::geometry));
                   st_astext
--------------------------------
 POLYGON((0 0,0 3,1 3,1 0,0 0))
(1 row)


SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))'::geometry));
                                                  st_astext
--------------------------------------------------------------
 POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
(1 row)
SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))'::geometry));
                                                  st_astext
--------------------------------------------------------------
 POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
(1 row)

SELECT Box3D(geom), Box2D(geom), ST_AsText(ST_Envelope(geom)) As envelopewkt
        FROM (SELECT 'POLYGON((0 0, 0 1000012333334.34545678, 1.0000001 1, 1.0000001 0, 0 0))'::geometry As geom) As foo;


        

Envelope of a point and linestring.

SELECT ST_AsText(ST_Envelope(
                ST_Collect(
                        ST_GeomFromText('LINESTRING(55 75,125 150)'),
                                ST_Point(20, 80))
                                )) As wktenv;
wktenv
-----------
POLYGON((20 75,20 150,125 150,125 75,20 75))

Name

ST_ExteriorRing — Returns a LineString representing the exterior ring of a Polygon.

Synopsis

geometry ST_ExteriorRing(geometry a_polygon);

Descrizione

Restituisce una LINESTRING che rappresenta l'anello esterno per una geometria POLYGON. Restituisce NULL se la geometria non è un poligono. Non funziona con MULTIPOLYGON

[Note]

Non funzionerà per i MULTIPOLYGON. Da utilizzare assieme a ST_Dump per i MULTIPOLYGON

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 8.2.3, 8.3.3

This function supports 3d and will not drop the z-index.

Esempi

--Se avete una tabella di poligoni:
SELECT gid, ST_ExteriorRing(the_geom) AS ering
FROM sometable;

--Se avete una tabella MULTIPOLYGON
--e volete riottenere un MULTILINESTRING composto dagli anelli esteriori mposed of the exterior rings of each polygon
SELECT gid, ST_Collect(ST_ExteriorRing(the_geom)) AS erings
        FROM (SELECT gid, (ST_Dump(the_geom)).geom As the_geom
                        FROM sometable) As foo
GROUP BY gid;

--Esempio 3d
SELECT ST_AsEWKT(
        ST_ExteriorRing(
        ST_GeomFromEWKT('POLYGON((0 0 1, 1 1 1, 1 2 1, 1 1 1, 0 0 1))')
        )
);

st_asewkt
---------
LINESTRING(0 0 1,1 1 1,1 2 1,1 1 1,0 0 1)

Name

ST_GeometryN — Restituisce il tipo di geometria per il valore ST_Geometry.

Synopsis

geometry ST_GeometryN(geometry geomA, integer n);

Descrizione

Restituisce la geometria numero N (a partire da 1) se la geometria è una GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE o (MULTI)POLYGON, POLYHEDRALSURFACE. Altrimenti restituisce il valore NULL.

[Note]

L'indice parte da 1, come per le specifiche OGC a partire dalla versione 0.8.0. Le precedenti versioni invece implementavano un indice a partire da zero.

[Note]

Se volete estrarre tutte le geometria, ST_Dump è più efficiente e funziona anche nel caso di geometrie singole.

Migliorato: Nella 2.0.0 è stato introdotto il supporto per le superfici poliedriche, i triangoli e i TIN.

Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi standard

--Extracting a subset of points from a 3d multipoint
SELECT n, ST_AsEWKT(ST_GeometryN(the_geom, n)) As geomewkt
FROM (
VALUES (ST_GeomFromEWKT('MULTIPOINT(1 2 7, 3 4 7, 5 6 7, 8 9 10)') ),
( ST_GeomFromEWKT('MULTICURVE(CIRCULARSTRING(2.5 2.5,4.5 2.5, 3.5 3.5), (10 11, 12 11))') )
        )As foo(the_geom)
        CROSS JOIN generate_series(1,100) n
WHERE n <= ST_NumGeometries(the_geom);

 n |               geomewkt
---+-----------------------------------------
 1 | POINT(1 2 7)
 2 | POINT(3 4 7)
 3 | POINT(5 6 7)
 4 | POINT(8 9 10)
 1 | CIRCULARSTRING(2.5 2.5,4.5 2.5,3.5 3.5)
 2 | LINESTRING(10 11,12 11)


--Extracting all geometries (useful when you want to assign an id)
SELECT gid, n, ST_GeometryN(the_geom, n)
FROM sometable CROSS JOIN generate_series(1,100) n
WHERE n <= ST_NumGeometries(the_geom);

Esempi con superfici poliedriche, TIN e triangoli

-- Polyhedral surface example
-- Break a Polyhedral surface into its faces
SELECT ST_AsEWKT(ST_GeometryN(p_geom,3)) As geom_ewkt
  FROM (SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
)')  AS p_geom )  AS a;

                geom_ewkt
------------------------------------------
 POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))
-- TIN --
SELECT ST_AsEWKT(ST_GeometryN(geom,2)) as wkt
  FROM
    (SELECT
       ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )')  AS geom
    ) AS g;
-- result --
                 wkt
-------------------------------------
 TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

Name

ST_GeometryType — Restituisce il tipo di geometria per il valore ST_Geometry.

Synopsis

text ST_GeometryType(geometry g1);

Descrizione

Restituisce il tipo di geometria come stringa. P. es.: 'ST_LineString', 'ST_Polygon','ST_MultiPolygon' ecc. Questa funzione differisce da GeometryType(geometry) per il prefisso ST che viene restituito, così come per il fatto che non indica se la geometria è misurata.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Esempi

SELECT ST_GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
                        --risultato
                        ST_LineString
SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
                        --result
                        ST_PolyhedralSurface
SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
                        --result
                        ST_PolyhedralSurface
SELECT ST_GeometryType(geom) as result
  FROM
    (SELECT
       ST_GeomFromEWKT('TIN (((
                0 0 0,
                0 0 1,
                0 1 0,
                0 0 0
            )), ((
                0 0 0,
                0 1 0,
                1 1 0,
                0 0 0
            ))
            )')  AS geom
    ) AS g;
 result
--------
 ST_Tin    

Si veda anche

GeometryType


Name

ST_HasArc — Tests if a geometry contains a circular arc

Synopsis

boolean ST_IsEmpty(geometry geomA);

Descrizione

Restituisce TRUE se la geometria è una geometrycollection, un poligono o un punto vuoto, ecc.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT ST_HasArc(ST_Collect('LINESTRING(1 2, 3 4, 5 6)', 'CIRCULARSTRING(1 1, 2 3, 4 5, 6 7, 5 6)'));
                st_hasarc
                --------
                t
                

Name

ST_InteriorRingN — Returns the Nth interior ring (hole) of a Polygon.

Synopsis

geometry ST_InteriorRingN(geometry a_polygon, integer n);

Descrizione

Restituisce una LINESTRING che rappresenta l'anello esterno per una geometria POLYGON. Restituisce NULL se la geometria non è un poligono. Non funziona con MULTIPOLYGON

[Note]

Non funzionerà per i MULTIPOLYGON. Da utilizzare assieme a ST_Dump per i MULTIPOLYGON

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_AsText(ST_InteriorRingN(the_geom, 1)) As the_geom
FROM (SELECT ST_BuildArea(
                ST_Collect(ST_Buffer(ST_Point(1,2), 20,3),
                        ST_Buffer(ST_Point(1, 2), 10,3))) As the_geom
                )  as foo
                

Name

ST_IsClosed — Restituisce TRUE se il punto iniziale e quello finale di LINESTRING coincidono. Per le superfici poliedriche indica una superficie chiusa (volumetrica).

Synopsis

boolean ST_IsClosed(geometry g);

Descrizione

Restituisce TRUE se il punto iniziale e quello finale di LINESTRING coincidono. Per le superfici poliedriche indicase la superficie è un'area (aperta) o un volume (chiusa).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.5, 9.3.3

[Note]

SQL-MM definisce il risultato di ST_IsClosed(NULL) come 0, mentre PostGIS restituisce NULL.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

This function supports Polyhedral surfaces.

Esempi con Stringhe di linee e punti

postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 1 1)'::geometry);
 st_isclosed
-------------
 f
(1 row)

postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 0 1, 1 1, 0 0)'::geometry);
 st_isclosed
-------------
 t
(1 row)

postgis=# SELECT ST_IsClosed('MULTILINESTRING((0 0, 0 1, 1 1, 0 0),(0 0, 1 1))'::geometry);
 st_isclosed
-------------
 f
(1 row)

postgis=# SELECT ST_IsClosed('POINT(0 0)'::geometry);
 st_isclosed
-------------
 t
(1 row)

postgis=# SELECT ST_IsClosed('MULTIPOINT((0 0), (1 1))'::geometry);
 st_isclosed
-------------
 t
(1 row)

Esempi con superfici poliedriche

-- A cube --
                SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));

 st_isclosed
-------------
 t


 -- Same as cube but missing a side --
 SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)) )'));

 st_isclosed
-------------
 f

Si veda anche

ST_IsRing


Name

ST_IsCollection — Restituisce TRUE se la geometria è una geometrycollection, un poligono o un punto vuoto, ecc.

Synopsis

boolean ST_IsCollection(geometry g);

Descrizione

Restituisce TRUE se il tipo di geometria è uno tra:

  • GEOMETRYCOLLECTION

  • MULTI{POINT,POLYGON,LINESTRING,CURVE,SURFACE}

  • COMPOUNDCURVE

[Note]

Questa funzione analizza il tipo di geometria. Significa che restituirà TRUE sulle collezioni che sono vuote o contengono un singolo elemento.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

postgis=# SELECT ST_IsCollection('LINESTRING(0 0, 1 1)'::geometry);
 st_iscollection
-------------
 f
(1 row)

postgis=# SELECT ST_IsCollection('MULTIPOINT EMPTY'::geometry);
 st_iscollection
-------------
 t
(1 row)

postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0))'::geometry);
 st_iscollection
-------------
 t
(1 row)

postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'::geometry);
 st_iscollection
-------------
 t
(1 row)

postgis=# SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'::geometry);
 st_iscollection
-------------
 t
(1 row)

Si veda anche

ST_NumGeometries


Name

ST_IsEmpty — Tests if a geometry is empty.

Synopsis

boolean ST_IsEmpty(geometry geomA);

Descrizione

Restituisce TRUE se la Geometry è una geometria vuota. Se è TRUE, allora questa Geometry rappresenta una geometria vuota (una collezione, un poligono, un punto, ecc.)

[Note]

SQL-MM definisce il risultato di ST_IsEmpty(NULL) come 0, mentre PostGIS restituisce NULL.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.7

This method supports Circular Strings and Curves

[Warning]

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards

Esempi

SELECT ST_IsEmpty(ST_GeomFromText('GEOMETRYCOLLECTION EMPTY'));
 st_isempty
------------
 t
(1 row)

 SELECT ST_IsEmpty(ST_GeomFromText('POLYGON EMPTY'));
 st_isempty
------------
 t
(1 row)

SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));

 st_isempty
------------
 f
(1 row)

 SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')) = false;
 ?column?
----------
 t
(1 row)

 SELECT ST_IsEmpty(ST_GeomFromText('CIRCULARSTRING EMPTY'));
  st_isempty
------------
 t
(1 row)


                

Name

ST_IsPolygonCCW — Tests if Polygons have exterior rings oriented counter-clockwise and interior rings oriented clockwise.

Synopsis

boolean ST_IsPolygonCCW ( geometry geom );

Descrizione

Returns true if all polygonal components of the input geometry use a counter-clockwise orientation for their exterior ring, and a clockwise direction for all interior rings.

Returns true if the geometry has no polygonal components.

[Note]

Closed linestrings are not considered polygonal components, so you would still get a true return by passing a single closed linestring no matter its orientation.

[Note]

If a polygonal geometry does not use reversed orientation for interior rings (i.e., if one or more interior rings are oriented in the same direction as an exterior ring) then both ST_IsPolygonCW and ST_IsPolygonCCW will return false.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_IsPolygonCW — Tests if Polygons have exterior rings oriented clockwise and interior rings oriented counter-clockwise.

Synopsis

boolean ST_IsPolygonCW ( geometry geom );

Descrizione

Returns true if all polygonal components of the input geometry use a clockwise orientation for their exterior ring, and a counter-clockwise direction for all interior rings.

Returns true if the geometry has no polygonal components.

[Note]

Closed linestrings are not considered polygonal components, so you would still get a true return by passing a single closed linestring no matter its orientation.

[Note]

If a polygonal geometry does not use reversed orientation for interior rings (i.e., if one or more interior rings are oriented in the same direction as an exterior ring) then both ST_IsPolygonCW and ST_IsPolygonCCW will return false.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_IsRing — Tests if a LineString is closed and simple.

Synopsis

boolean ST_IsRing(geometry g);

Descrizione

Restituisce TRUE se questa LINESTRING è sia ST_IsClosed (ST_StartPoint(g) ~= ST_Endpoint(g)) che ST_IsSimple (non interseca se stessa).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.6

[Note]

SQL-MM defines the result of ST_IsRing(NULL) to be 0, while PostGIS returns NULL.

Esempi

SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)
FROM (SELECT 'LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'::geometry AS the_geom) AS foo;
 st_isring | st_isclosed | st_issimple
-----------+-------------+-------------
 t         | t           | t
(1 row)

SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)
FROM (SELECT 'LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)'::geometry AS the_geom) AS foo;
 st_isring | st_isclosed | st_issimple
-----------+-------------+-------------
 f         | t           | f
(1 row)

Name

ST_IsSimple — Tests if a geometry has no points of self-intersection or self-tangency.

Synopsis

boolean ST_IsSimple(geometry geomA);

Descrizione

Returns true if this Geometry has no anomalous geometric points, such as self intersection or self tangency. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"

[Note]

SQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.8

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_IsSimple(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));
 st_issimple
-------------
 t
(1 row)

 SELECT ST_IsSimple(ST_GeomFromText('LINESTRING(1 1,2 2,2 3.5,1 3,1 2,2 1)'));
 st_issimple
-------------
 f
(1 row)

Si veda anche

ST_IsValid


Name

ST_M — Returns the M coordinate of a Point.

Synopsis

float ST_M(geometry a_point);

Descrizione

Restituisce la coordinata X del punto, o NULL se non disponibile. L'input deve essere un punto.

[Note]

This is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_M(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_m
------
        4
(1 row)

                

Si veda anche

ST_GeomFromEWKT, ST_X, ST_Y, ST_Z


Name

ST_MemSize — Restituisce il tipo di geometria per il valore ST_Geometry.

Synopsis

integer ST_NRings(geometry geomA);

Descrizione

Restituisce il tipo di geometria per il valore ST_Geometry.

This complements the PostgreSQL built-in database object functions pg_column_size, pg_size_pretty, pg_relation_size, pg_total_relation_size.

[Note]

pg_relation_size which gives the byte size of a table may return byte size lower than ST_MemSize. This is because pg_relation_size does not add toasted table contribution and large geometries are stored in TOAST tables.

pg_total_relation_size - includes, the table, the toasted tables, and the indexes.

pg_column_size returns how much space a geometry would take in a column considering compression, so may be lower than ST_MemSize

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Changed: 2.2.0 name changed to ST_MemSize to follow naming convention.

Esempi

--Return how much byte space Boston takes up  in our Mass data set
SELECT pg_size_pretty(SUM(ST_MemSize(the_geom))) as totgeomsum,
pg_size_pretty(SUM(CASE WHEN town = 'BOSTON' THEN ST_MemSize(the_geom) ELSE 0 END)) As bossum,
CAST(SUM(CASE WHEN town = 'BOSTON' THEN ST_MemSize(the_geom) ELSE 0 END)*1.00 /
                SUM(ST_MemSize(the_geom))*100 As numeric(10,2)) As perbos
FROM towns;

totgeomsum        bossum        perbos
----------        ------        ------
1522 kB                30 kB        1.99


SELECT ST_MemSize(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'));

---
73

--What percentage of our table is taken up by just the geometry
SELECT pg_total_relation_size('public.neighborhoods') As fulltable_size, sum(ST_MemSize(the_geom)) As geomsize,
sum(ST_MemSize(the_geom))*1.00/pg_total_relation_size('public.neighborhoods')*100 As pergeom
FROM neighborhoods;
fulltable_size geomsize  pergeom
------------------------------------------------
262144         96238         36.71188354492187500000
        

Name

ST_NDims —

Restituisce la dimensione delle coordinate di ST_Geometry value.

Synopsis

integer ST_NDims(geometry g1);

Descrizione

Returns the coordinate dimension of the geometry. PostGIS supports 2 - (x,y) , 3 - (x,y,z) or 2D with measure - x,y,m, and 4 - 3D with measure space x,y,z,m

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_NDims(ST_GeomFromText('POINT(1 1)')) As d2point,
        ST_NDims(ST_GeomFromEWKT('POINT(1 1 2)')) As d3point,
        ST_NDims(ST_GeomFromEWKT('POINTM(1 1 0.5)')) As d2pointm;

         d2point | d3point | d2pointm
---------+---------+----------
           2 |       3 |        3
                        

Name

ST_NPoints — Returns the number of points (vertices) in a geometry.

Synopsis

integer ST_NPoints(geometry g1);

Descrizione

Return the number of points in a geometry. Works for all geometries.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_NPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
--result
4

--Poligono nello spazio 3D
SELECT ST_NPoints(ST_GeomFromEWKT('LINESTRING(77.29 29.07 1,77.42 29.26 0,77.27 29.31 -1,77.29 29.07 3)'))
--result
4

Si veda anche

ST_NumPoints


Name

ST_NRings — Returns the number of rings in a polygonal geometry.

Synopsis

integer ST_NRings(geometry geomA);

Descrizione

If the geometry is a polygon or multi-polygon returns the number of rings. Unlike NumInteriorRings, it counts the outer rings as well.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT ST_NRings(the_geom) As Nrings, ST_NumInteriorRings(the_geom) As ninterrings
                                        FROM (SELECT ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))') As the_geom) As foo;
         nrings | ninterrings
--------+-------------
          1 |           0
(1 row)

Si veda anche

ST_NumInteriorRings


Name

ST_NumGeometries — Restituisce TRUE se la geometria è una geometrycollection, un poligono o un punto vuoto, ecc.

Synopsis

integer ST_NumGeometries(geometry geom);

Descrizione

Returns the number of Geometries. If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL.

Migliorato: Nella 2.0.0 è stato introdotto il supporto per le superfici poliedriche, i triangoli e i TIN.

Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

--Prior versions would have returned NULL for this -- in 2.0.0 this returns 1
SELECT ST_NumGeometries(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
--result
1

--Geometry Collection Example - multis count as one geom in a collection
SELECT ST_NumGeometries(ST_GeomFromEWKT('GEOMETRYCOLLECTION(MULTIPOINT(-2 3 , -2 2),
LINESTRING(5 5 ,10 10),
POLYGON((-7 4.2,-7.1 5,-7.1 4.3,-7 4.2)))'));
--result
3

Si veda anche

ST_GeometryN, ST_Multi


Name

ST_NumInteriorRings — Returns the number of interior rings (holes) of a Polygon.

Synopsis

integer ST_NumInteriorRings(geometry a_polygon);

Descrizione

Return the number of interior rings of a polygon geometry. Return NULL if the geometry is not a polygon.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.5

Changed: 2.0.0 - in prior versions it would allow passing a MULTIPOLYGON, returning the number of interior rings of first POLYGON.

Esempi

--If you have a regular polygon
SELECT gid, field1, field2, ST_NumInteriorRings(the_geom) AS numholes
FROM sometable;

--If you have multipolygons
--And you want to know the total number of interior rings in the MULTIPOLYGON
SELECT gid, field1, field2, SUM(ST_NumInteriorRings(the_geom)) AS numholes
FROM (SELECT gid, field1, field2, (ST_Dump(the_geom)).geom As the_geom
        FROM sometable) As foo
GROUP BY gid, field1,field2;
                        

Name

ST_NumInteriorRing — Returns the number of interior rings (holes) of a Polygon. Aias for ST_NumInteriorRings

Synopsis

integer ST_NumInteriorRing(geometry a_polygon);


Name

ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.

Synopsis

integer ST_NumPatches(geometry g1);

Descrizione

Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This is an alias for ST_NumGeometries to support MM naming. Faster to use ST_NumGeometries if you don't care about MM convention.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: ?

This function supports Polyhedral surfaces.

Esempi

SELECT ST_NumPatches(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
                --result
                6
                

Name

ST_NumPoints — Returns the number of points in a LineString or CircularString.

Synopsis

integer ST_NumPoints(geometry g1);

Descrizione

Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with Linestrings as the specs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertexes for not just line strings. Consider using ST_NPoints instead which is multi-purpose and works with many geometry types.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.4

Esempi

SELECT ST_NumPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
                --result
                4
                

Si veda anche

ST_NPoints


Name

ST_PatchN — Restituisce il tipo di geometria per il valore ST_Geometry.

Synopsis

geometry ST_PatchN(geometry geomA, integer n);

Descrizione

Returns the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE or POLYHEDRALSURFACEM. Otherwise, returns NULL. This returns the same answer as ST_GeometryN for PolyhedralSurfaces. Using ST_GeometryN is faster.

[Note]

L'indice parte da 1.

[Note]

Se volete estrarre tutte le geometria, ST_Dump è più efficiente e funziona anche nel caso di geometrie singole.

Disponibilità: 2.0

This method implements the SQL/MM specification. SQL-MM 3: ?

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Esempi

--Extract the 2nd face of the polyhedral surface
SELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewkt
FROM (
VALUES (ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
        ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
        ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
        ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ) As foo(geom);

              geomewkt
---+-----------------------------------------
 POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

Name

ST_PointN — Returns the Nth point in the first LineString or circular LineString in a geometry.

Synopsis

geometry ST_PointN(geometry a_linestring, integer n);

Descrizione

Return the Nth point in a single linestring or circular linestring in the geometry. Negative values are counted backwards from the end of the LineString, so that -1 is the last point. Returns NULL if there is no linestring in the geometry.

[Note]

Index is 1-based as for OGC specs since version 0.8.0. Backward indexing (negative index) is not in OGC Previous versions implemented this as 0-based instead.

[Note]

If you want to get the Nth point of each LineString in a MultiLineString, use in conjunction with ST_Dump

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.5, 7.3.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring.

Changed: 2.3.0 : negative indexing available (-1 is last point)

Esempi

-- Extract all POINTs from a LINESTRING
SELECT ST_AsText(
   ST_PointN(
          column1,
          generate_series(1, ST_NPoints(column1))
   ))
FROM ( VALUES ('LINESTRING(0 0, 1 1, 2 2)'::geometry) ) AS foo;

 st_astext
------------
 POINT(0 0)
 POINT(1 1)
 POINT(2 2)
(3 rows)

--Example circular string
SELECT ST_AsText(ST_PointN(ST_GeomFromText('CIRCULARSTRING(1 2, 3 2, 1 2)'), 2));

 st_astext
------------
 POINT(3 2)
(1 row)

SELECT ST_AsText(f)
FROM ST_GeomFromText('LINESTRING(0 0 0, 1 1 1, 2 2 2)') AS g
  ,ST_PointN(g, -2) AS f; -- 1 based index

    st_astext
-----------------
 POINT Z (1 1 1)
(1 row)

Si veda anche

ST_NPoints


Name

ST_Points —

Restituisce la dimensione delle coordinate di ST_Geometry value.

Synopsis

geometry ST_Points( geometry geom );

Descrizione

Returns a MultiPoint containing all the coordinates of a geometry. Does not remove points that are repeated in the geometry, including the start and end points of ring geometries. (If this behavior is undesired, duplicates may be removed using ST_RemovePoint).

To obtain information about the position of each coordinate in the parent geometry use ST_NumPoints.

M and Z coordinates will be preserved if present.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

Availability: 2.3.0

Esempi

SELECT ST_AsText(ST_Points('POLYGON Z ((30 10 4,10 30 5,40 40 6, 30 10))'));

--result
MULTIPOINT Z (30 10 4,10 30 5,40 40 6, 30 10 4)
                        

Name

ST_StartPoint — Returns the first point of a LineString.

Synopsis

geometry ST_StartPoint(geometry geomA);

Descrizione

Returns the first point of a LINESTRING or CIRCULARLINESTRING geometry as a POINT. Returns NULL if the input is not a LINESTRING or CIRCULARLINESTRING.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.3

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

[Note]

Modifica: La versione 2.0.0 non funziona più con geometrie singole di stringhe multilinea. Nelle versioni precedenti di PostGIS una stringa multilinea con una sola linea avrebbe funzionato tranquillamente con questa funzione, restituendo il punto di inizio. Nella versione 2.0.0 la funzione restituisce NULL come per qualsiasi altra stringa multilinea. Il comportamento precedente non era documentato, ma le persone che presumevano di avere i dati memorizzati come LINESTRING potrebbero trovare che questi ora restituiscono il valore NULL.

Esempi

Start point of a LineString

SELECT ST_AsText(ST_StartPoint('LINESTRING(0 1, 0 2)'::geometry));
 st_astext
------------
 POINT(0 1)

Start point of a non-LineString is NULL

SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null;
  is_null
----------
 t

Start point of a 3D LineString

SELECT ST_AsEWKT(ST_StartPoint('LINESTRING(0 1 1, 0 2 2)'::geometry));
 st_asewkt
------------
 POINT(0 1 1)

Start point of a CircularString

SELECT ST_AsText(ST_StartPoint('CIRCULARSTRING(5 2,-3 1.999999, -2 1, -4 2, 6 3)'::geometry));
 st_astext
------------
 POINT(5 2)

Si veda anche

ST_EndPoint, ST_PointN


Name

ST_Summary — Returns a text summary of the contents of a geometry.

Synopsis

text ST_Summary(geometry g);

text ST_Summary(geography g);

Descrizione

Restituisce il tipo di geometria per il valore ST_Geometry.

Flags shown square brackets after the geometry type have the following meaning:

  • M: has M coordinate

  • Z: has Z coordinate

  • B: has a cached bounding box

  • G: is geodetic (geography)

  • S: has spatial reference system

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Availability: 1.2.2

Enhanced: 2.0.0 added support for geography

Enhanced: 2.1.0 S flag to denote if has a known spatial reference system

Enhanced: 2.2.0 Added support for TIN and Curves

Esempi

=# SELECT ST_Summary(ST_GeomFromText('LINESTRING(0 0, 1 1)')) as geom,
        ST_Summary(ST_GeogFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) geog;
            geom             |          geog
-----------------------------+--------------------------
 LineString[B] with 2 points | Polygon[BGS] with 1 rings
                             | ring 0 has 5 points
                             :
(1 row)


=# SELECT ST_Summary(ST_GeogFromText('LINESTRING(0 0 1, 1 1 1)')) As geog_line,
        ST_Summary(ST_GeomFromText('SRID=4326;POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))')) As geom_poly;
;
           geog_line             |        geom_poly
-------------------------------- +--------------------------
 LineString[ZBGS] with 2 points | Polygon[ZBS] with 1 rings
                                :    ring 0 has 5 points
                                :
(1 row)


Name

ST_X — Returns the X coordinate of a Point.

Synopsis

float ST_X(geometry a_point);

Descrizione

Restituisce la coordinata X del punto, o NULL se non disponibile. L'input deve essere un punto.

[Note]

To get the minimum and maximum X value of geometry coordinates use the functions ST_XMin and ST_XMax.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.3

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_X(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_x
------
        1
(1 row)

SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
 st_y
------
  1.5
(1 row)

                

Name

ST_Y — Returns the Y coordinate of a Point.

Synopsis

float ST_Y(geometry a_point);

Descrizione

Restituisce la coordinata X del punto, o NULL se non disponibile. L'input deve essere un punto.

[Note]

To get the minimum and maximum Y value of geometry coordinates use the functions ST_YMin and ST_YMax.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.4

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_Y(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_y
------
        2
(1 row)

SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
 st_y
------
  1.5
(1 row)


                

Name

ST_Z — Returns the Z coordinate of a Point.

Synopsis

float ST_Z(geometry a_point);

Descrizione

Restituisce la coordinata X del punto, o NULL se non disponibile. L'input deve essere un punto.

[Note]

To get the minimum and maximum Z value of geometry coordinates use the functions ST_ZMin and ST_ZMax.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_Z(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_z
------
        3
(1 row)

                

Name

ST_Zmflag — Restituisce la dimensione delle coordinate di ST_Geometry value.

Synopsis

smallint ST_Zmflag(geometry geomA);

Descrizione

Restituisce la dimensione delle coordinate di ST_Geometry value.

Values are: 0 = 2D, 1 = 3D-M, 2 = 3D-Z, 3 = 4D.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRING(1 2, 3 4)'));
 st_zmflag
-----------
                 0

SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRINGM(1 2 3, 3 4 3)'));
 st_zmflag
-----------
                 1

SELECT ST_Zmflag(ST_GeomFromEWKT('CIRCULARSTRING(1 2 3, 3 4 3, 5 6 3)'));
 st_zmflag
-----------
                 2
SELECT ST_Zmflag(ST_GeomFromEWKT('POINT(1 2 3 4)'));
 st_zmflag
-----------
                 3

8.5. Geometry Editors

Abstract

These functions create modified geometries by changing type, structure or vertices.

ST_AddPoint — Add a point to a LineString.
ST_CollectionExtract — Given a geometry collection, returns a multi-geometry containing only elements of a specified type.
ST_CollectionHomogenize — Returns the simplest representation of a geometry collection.
ST_CurveToLine — Converts a geometry containing curves to a linear geometry.
ST_FlipCoordinates — Returns a version of a geometry with X and Y axis flipped.
ST_Force2D — Force the geometries into a "2-dimensional mode".
ST_Force3D — Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
ST_Force3DZ — Force the geometries into XYZ mode.
ST_Force3DM — Force the geometries into XYM mode.
ST_Force4D — Force the geometries into XYZM mode.
ST_ForcePolygonCCW — Orients all exterior rings counter-clockwise and all interior rings clockwise.
ST_ForceCollection — Convert the geometry into a GEOMETRYCOLLECTION.
ST_ForcePolygonCW — Orients all exterior rings clockwise and all interior rings counter-clockwise.
ST_ForceSFS — Force the geometries to use SFS 1.1 geometry types only.
ST_ForceRHR — Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
ST_ForceCurve — Upcast a geometry into its curved type, if applicable.
ST_LineMerge — Converts a linear geometry to a curved geometry.
ST_Multi — Return the geometry as a MULTI* geometry.
ST_Normalize — Return the geometry in its canonical form.
ST_QuantizeCoordinates — Sets least significant bits of coordinates to zero
ST_RemovePoint — Remove a point from a linestring.
ST_RemovePoint — Returns a version of the given geometry with duplicated points removed.
ST_Reverse — Return the geometry with vertex order reversed.
ST_Segmentize — Return a modified geometry/geography having no segment longer than the given distance.
ST_SetPoint — Replace point of a linestring with a given point.
ST_ShiftLongitude — Shifts a geometry with geographic coordinates between -180..180 and 0..360.
ST_WrapX — Wrap a geometry around an X value.
ST_SnapToGrid — Snap all points of the input geometry to a regular grid.
ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.
ST_SwapOrdinates — Returns a version of the given geometry with given ordinate values swapped.

Name

ST_AddPoint — Add a point to a LineString.

Synopsis

geometry ST_AddPoint(geometry linestring, geometry point);

geometry ST_AddPoint(geometry linestring, geometry point, integer position);

Descrizione

Adds a point to a LineString before the index position (using a 0-based index). If the position parameter is omitted or is -1 the point is appended to the end of the LineString.

Disponibilità: 1.1.0

This function supports 3d and will not drop the z-index.

Esempi

Add a point to the end of a 3D line

SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
        st_asewkt
        ---------
        POINT(5 12 3)

Guarantee all lines in a table are closed by adding the start point of each line to the end of the line only for those that are not closed.

UPDATE sometable
SET the_geom = ST_AddPoint(the_geom, ST_StartPoint(the_geom))
FROM sometable
WHERE ST_IsClosed(the_geom) = false;

Name

ST_CollectionExtract — Given a geometry collection, returns a multi-geometry containing only elements of a specified type.

Synopsis

geometry ST_CollectionHomogenize(geometry collection);

geometry ST_CollectionExtract(geometry collection, integer type);

Descrizione

Given a geometry collection, returns a homogeneous multi-geometry.

If the type is not specified, returns a multi-geometry containing only geometries of the highest dimension. So polygons are preferred over lines, which are preferred over points.

If the type is specified, returns a multi-geometry containing only that type. If there are no sub-geometries of the right type, an EMPTY geometry is returned. Only points, lines and polygons are supported. The type numbers are:

  • 1 == POINT

  • 2 == LINESTRING

  • 3 == POLYGON

For atomic geometry inputs, the geometry is retured unchanged if the input type matches the requested type. Otherwise, the result is an EMPTY geometry of the specified type. If required, these can be converted to multi-geometries using ST_Multi.

[Warning]

MultiPolygon results are not checked for validity. If the polygon components are adjacent or overlapping the result will be invalid. (For example, this can occur when applying this function to an ST_Split result.) This situation can be checked with ST_IsValid and repaired with ST_MakeValid.

Disponibilità: 1.5.0

[Note]

Prior to 1.5.3 this function returned atomic inputs unchaanged, no matter type. In 1.5.3 non-matching single geometries returned a NULL result. In 2.0.0 non-matching single geometries return an EMPTY result of the requested type.

Esempi

Extract highest-dimension type:

SELECT ST_AsText(ST_CollectionExtract(
        'GEOMETRYCOLLECTION( POINT(0 0), LINESTRING(1 1, 2 2) )'));
    st_astext
    ---------------
    MULTILINESTRING((1 1, 2 2))

Extract points (type 1 == POINT):

SELECT ST_AsText(ST_CollectionExtract(
        'GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(POINT(0 0)))',
        1 ));
    st_astext
    ---------------
    MULTIPOINT(0 0)

Extract lines (type 2 == LINESTRING):

SELECT ST_AsText(ST_CollectionExtract(
        'GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(LINESTRING(0 0, 1 1)),LINESTRING(2 2, 3 3))',
        2 ));
    st_astext
    ---------------
    MULTILINESTRING((0 0, 1 1), (2 2, 3 3))

Name

ST_CollectionHomogenize — Returns the simplest representation of a geometry collection.

Synopsis

geometry ST_CollectionHomogenize(geometry collection);

Descrizione

Given a geometry collection, returns the "simplest" representation of the contents.

  • Homogeneous (uniform) collections are returned as the appropriate multi-geometry.

  • Heterogeneous (mixed) collections are flattened into a single GeometryCollection.

  • Collections containing a single atomic element are returned as that element.

  • Atomic geometries are returned unchanged. If required, these can be converted to a multi-geometry using ST_Multi.

[Warning]

This function does not ensure that the result is valid. In particular, a collection containing adjacent or overlapping Polygons will create an invalid MultiPolygon. This situation can be checked with ST_IsValid and repaired with ST_MakeValid.

Disponibilità: 2.0

Esempi

Single-element collection converted to an atomic geometry

SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
        st_asewkt
        ---------
        POINT(5 12 3)

Nested single-element collection converted to an atomic geometry:

SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
        st_asewkt
        ---------
        POINT(5 12 3)

Collection converted to a multi-geometry:

SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
        st_asewkt
        ---------
        POINT(5 12 3)

Nested heterogeneous collection flattened to a GeometryCollection:

SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0), GEOMETRYCOLLECTION( LINESTRING(1 1, 2 2)))'));

        st_astext
        ---------------------
        GEOMETRYCOLLECTION(POINT(0 0),LINESTRING(1 1,2 2))

Collection of Polygons converted to an (invalid) MultiPolygon:

SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION (POLYGON ((10 50, 50 50, 50 10, 10 10, 10 50)), POLYGON ((90 50, 90 10, 50 10, 50 50, 90 50)))'));

        st_astext
        ---------------------
        MULTIPOLYGON(((10 50,50 50,50 10,10 10,10 50)),((90 50,90 10,50 10,50 50,90 50)))

Name

ST_CurveToLine — Converts a geometry containing curves to a linear geometry.

Synopsis

geometry ST_TransScale(geometry geomA, float deltaX, float deltaY, float XFactor, float YFactor);

Descrizione

Converts a CIRCULAR STRING to regular LINESTRING or CURVEPOLYGON to POLYGON or MULTISURFACE to MULTIPOLYGON. Useful for outputting to devices that can't support CIRCULARSTRING geometry types

Converts a given geometry to a linear geometry. Each curved geometry or segment is converted into a linear approximation using the given `tolerance` and options (32 segments per quadrant and no options by default).

The 'tolerance_type' argument determines interpretation of the `tolerance` argument. It can take the following values:

  • 0 (default): Tolerance is max segments per quadrant.

  • 1: Tolerance is max-deviation of line from curve, in source units.

  • 2: Tolerance is max-angle, in radians, between generating radii.

The 'flags' argument is a bitfield. 0 by default. Supported bits are:

  • 1: Symmetric (orientation idependent) output.

  • 2: Retain angle, avoids reducing angles (segment lengths) when producing symmetric output. Has no effect when Symmetric flag is off.

Disponibilità: 1.1.0

Enhanced: 2.4.0 added support for max-deviation and max-angle tolerance, and for symmetric output.

Enhanced: 3.0.0 implemented a minimum number of segments per linearized arc to prevent topological collapse.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.6

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)')));

--Result --
 LINESTRING(220268 150415,220269.95064912 150416.539364228,220271.823415575 150418.17258804,220273.613787707 150419.895736857,
 220275.317452352 150421.704659462,220276.930305234 150423.594998003,220278.448460847 150425.562198489,
 220279.868261823 150427.60152176,220281.186287736 150429.708054909,220282.399363347 150431.876723113,
 220283.50456625 150434.10230186,220284.499233914 150436.379429536,220285.380970099 150438.702620341,220286.147650624 150441.066277505,
 220286.797428488 150443.464706771,220287.328738321 150445.892130112,220287.740300149 150448.342699654,
 220288.031122486 150450.810511759,220288.200504713 150453.289621251,220288.248038775 150455.77405574,
 220288.173610157 150458.257830005,220287.977398166 150460.734960415,220287.659875492 150463.199479347,
 220287.221807076 150465.64544956,220286.664248262 150468.066978495,220285.988542259 150470.458232479,220285.196316903 150472.81345077,
 220284.289480732 150475.126959442,220283.270218395 150477.39318505,220282.140985384 150479.606668057,
 220280.90450212 150481.762075989,220279.5637474 150483.85421628,220278.12195122 150485.87804878,
 220276.582586992 150487.828697901,220274.949363179 150489.701464356,220273.226214362 150491.491836488,
 220271.417291757 150493.195501133,220269.526953216 150494.808354014,220267.559752731 150496.326509628,
 220265.520429459 150497.746310603,220263.41389631 150499.064336517,220261.245228106 150500.277412127,
 220259.019649359 150501.38261503,220256.742521683 150502.377282695,220254.419330878 150503.259018879,
 220252.055673714 150504.025699404,220249.657244448 150504.675477269,220247.229821107 150505.206787101,
 220244.779251566 150505.61834893,220242.311439461 150505.909171266,220239.832329968 150506.078553494,
 220237.347895479 150506.126087555,220234.864121215 150506.051658938,220232.386990804 150505.855446946,
 220229.922471872 150505.537924272,220227.47650166 150505.099855856,220225.054972724 150504.542297043,
 220222.663718741 150503.86659104,220220.308500449 150503.074365683,
 220217.994991777 150502.167529512,220215.72876617 150501.148267175,
 220213.515283163 150500.019034164,220211.35987523 150498.7825509,
 220209.267734939 150497.441796181,220207.243902439 150496,
 220205.293253319 150494.460635772,220203.420486864 150492.82741196,220201.630114732 150491.104263143,
 220199.926450087 150489.295340538,220198.313597205 150487.405001997,220196.795441592 150485.437801511,
 220195.375640616 150483.39847824,220194.057614703 150481.291945091,220192.844539092 150479.123276887,220191.739336189 150476.89769814,
 220190.744668525 150474.620570464,220189.86293234 150472.297379659,220189.096251815 150469.933722495,
 220188.446473951 150467.535293229,220187.915164118 150465.107869888,220187.50360229 150462.657300346,
 220187.212779953 150460.189488241,220187.043397726 150457.710378749,220186.995863664 150455.22594426,
 220187.070292282 150452.742169995,220187.266504273 150450.265039585,220187.584026947 150447.800520653,
 220188.022095363 150445.35455044,220188.579654177 150442.933021505,220189.25536018 150440.541767521,
 220190.047585536 150438.18654923,220190.954421707 150435.873040558,220191.973684044 150433.60681495,
 220193.102917055 150431.393331943,220194.339400319 150429.237924011,220195.680155039 150427.14578372,220197.12195122 150425.12195122,
 220198.661315447 150423.171302099,220200.29453926 150421.298535644,220202.017688077 150419.508163512,220203.826610682 150417.804498867,
 220205.716949223 150416.191645986,220207.684149708 150414.673490372,220209.72347298 150413.253689397,220211.830006129 150411.935663483,
 220213.998674333 150410.722587873,220216.22425308 150409.61738497,220218.501380756 150408.622717305,220220.824571561 150407.740981121,
 220223.188228725 150406.974300596,220225.586657991 150406.324522731,220227 150406)

--3d example
SELECT ST_AsEWKT(ST_CurveToLine(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')));
Output
------
 LINESTRING(220268 150415 1,220269.95064912 150416.539364228 1.0181172856673,
 220271.823415575 150418.17258804 1.03623457133459,220273.613787707 150419.895736857 1.05435185700189,....AD INFINITUM ....
    220225.586657991 150406.324522731 1.32611114201132,220227 150406 3)

--use only 2 segments to approximate quarter circle
SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'),2));
st_astext
------------------------------
 LINESTRING(220268 150415,220287.740300149 150448.342699654,220278.12195122 150485.87804878,
 220244.779251566 150505.61834893,220207.243902439 150496,220187.50360229 150462.657300346,
 220197.12195122 150425.12195122,220227 150406)

-- Ensure approximated line is no further than 20 units away from
-- original curve, and make the result direction-neutral
SELECT ST_AsText(ST_CurveToLine(
 'CIRCULARSTRING(0 0,100 -100,200 0)'::geometry,
    20, -- Tolerance
    1, -- Above is max distance between curve and line
    1  -- Symmetric flag
));
st_astext
-------------------------------------------------------------------------------------------
 LINESTRING(0 0,50 -86.6025403784438,150 -86.6025403784439,200 -1.1331077795296e-13,200 0)


        

Si veda anche

ST_LineMerge


Name

ST_FlipCoordinates — Returns a version of a geometry with X and Y axis flipped.

Synopsis

geometry ST_Multi(geometry g1);

Descrizione

Returns a version of the given geometry with X and Y axis flipped. Useful for fixing geometries which contain coordinates expressed as latitude/longitude (Y,X).

Disponibilità: 2.0

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

SELECT ST_AsEWKT(ST_FlipCoordinates(GeomFromEWKT('POINT(1 2)')));
 st_asewkt
------------
POINT(2 1)
         

Si veda anche

ST_SwapOrdinates


Name

ST_Force2D — Force the geometries into a "2-dimensional mode".

Synopsis

geometry ST_Force2D(geometry geomA);

Descrizione

Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates. This is useful for force OGC-compliant output (since OGC only specifies 2-D geometries).

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_2D.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_AsEWKT(ST_Force2D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
                st_asewkt
-------------------------------------
CIRCULARSTRING(1 1,2 3,4 5,6 7,5 6)

SELECT  ST_AsEWKT(ST_Force2D('POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))'));

                                  st_asewkt
----------------------------------------------
 POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))

                

Si veda anche

ST_Force3D


Name

ST_Force3D — Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.

Synopsis

geometry ST_RotateX(geometry geomA, float rotRadians);

Descrizione

Forces the geometries into XYZ mode. This is an alias for ST_Force3DZ. If a geometry has no Z component, then a Zvalue Z coordinate is tacked on.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3D.

Changed: 3.1.0. Added support for supplying a non-zero Z value.

This function supports Polyhedral surfaces.

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

Esempi

--Nothing happens to an already 3D geometry
                SELECT ST_AsEWKT(ST_Force3D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
                                   st_asewkt
-----------------------------------------------
 CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)


SELECT  ST_AsEWKT(ST_Force3D('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

                                                 st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))
                

Name

ST_Force3DZ — Force the geometries into XYZ mode.

Synopsis

geometry ST_RotateZ(geometry geomA, float rotRadians);

Descrizione

Forces the geometries into XYZ mode. If a geometry has no Z component, then a Zvalue Z coordinate is tacked on.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DZ.

Changed: 3.1.0. Added support for supplying a non-zero Z value.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

--Nothing happens to an already 3D geometry
SELECT ST_AsEWKT(ST_Force3DZ(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
                                   st_asewkt
-----------------------------------------------
 CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)


SELECT  ST_AsEWKT(ST_Force3DZ('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

                                                 st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))
                

Name

ST_Force3DM — Force the geometries into XYM mode.

Synopsis

geometry ST_RotateX(geometry geomA, float rotRadians);

Descrizione

Forces the geometries into XYM mode. If a geometry has no M component, then a Mvalue M coordinate is tacked on. If it has a Z component, then Z is removed

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DM.

Changed: 3.1.0. Added support for supplying a non-zero M value.

This method supports Circular Strings and Curves

Esempi

--Nothing happens to an already 3D geometry
SELECT ST_AsEWKT(ST_Force3DM(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
                                   st_asewkt
------------------------------------------------
 CIRCULARSTRINGM(1 1 0,2 3 0,4 5 0,6 7 0,5 6 0)


SELECT  ST_AsEWKT(ST_Force3DM('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

                                                  st_asewkt
---------------------------------------------------------------
 POLYGONM((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

                

Name

ST_Force4D — Force the geometries into XYZM mode.

Synopsis

geometry ST_Snap(geometry input, geometry reference, float tolerance);

Descrizione

Forces the geometries into XYZM mode. Zvalue and Mvalue is tacked on for missing Z and M dimensions, respectively.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_4D.

Changed: 3.1.0. Added support for supplying non-zero Z and M values.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

--Nothing happens to an already 3D geometry
SELECT ST_AsEWKT(ST_Force4D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
                                                st_asewkt
---------------------------------------------------------
 CIRCULARSTRING(1 1 2 0,2 3 2 0,4 5 2 0,6 7 2 0,5 6 2 0)



SELECT  ST_AsEWKT(ST_Force4D('MULTILINESTRINGM((0 0 1,0 5 2,5 0 3,0 0 4),(1 1 1,3 1 1,1 3 1,1 1 1))'));

                                                                          st_asewkt
--------------------------------------------------------------------------------------
 MULTILINESTRING((0 0 0 1,0 5 0 2,5 0 0 3,0 0 0 4),(1 1 0 1,3 1 0 1,1 3 0 1,1 1 0 1))

                

Name

ST_ForcePolygonCCW — Orients all exterior rings counter-clockwise and all interior rings clockwise.

Synopsis

geometry ST_ForcePolygonCCW ( geometry geom );

Descrizione

Forces (Multi)Polygons to use a counter-clockwise orientation for their exterior ring, and a clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_ForceCollection — Convert the geometry into a GEOMETRYCOLLECTION.

Synopsis

geometry ST_ForceCollection(geometry geomA);

Descrizione

Converts the geometry into a GEOMETRYCOLLECTION. This is useful for simplifying the WKB representation.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

Availability: 1.2.2, prior to 1.3.4 this function will crash with Curves. This is fixed in 1.3.4+

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_Collection.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT  ST_AsEWKT(ST_ForceCollection('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

                                                                   st_asewkt
----------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1)))


  SELECT ST_AsText(ST_ForceCollection('CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));
                                                                   st_astext
--------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))
(1 row)

                
-- POLYHEDRAL example --
SELECT ST_AsEWKT(ST_ForceCollection('POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
 ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
 ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
 ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
 ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
 ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))'))

                                                                   st_asewkt
----------------------------------------------------------------------------------
GEOMETRYCOLLECTION(
  POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
  POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
  POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
  POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
  POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
  POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))
)
                

Name

ST_ForcePolygonCW — Orients all exterior rings clockwise and all interior rings counter-clockwise.

Synopsis

geometry ST_ForcePolygonCW ( geometry geom );

Descrizione

Forces (Multi)Polygons to use a clockwise orientation for their exterior ring, and a counter-clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.


Name

ST_ForceSFS — Force the geometries to use SFS 1.1 geometry types only.

Synopsis

geometry ST_ForceSFS(geometry geomA);

geometry ST_ForceSFS(geometry geomA, text version);

Descrizione

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.


Name

ST_ForceRHR — Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.

Synopsis

geometry ST_ForceRHR(geometry g);

Descrizione

Forces the orientation of the vertices in a polygon to follow a Right-Hand-Rule, in which the area that is bounded by the polygon is to the right of the boundary. In particular, the exterior ring is orientated in a clockwise direction and the interior rings in a counter-clockwise direction. This function is a synonym for ST_ForcePolygonCW

[Note]

The above definition of the Right-Hand-Rule conflicts with definitions used in other contexts. To avoid confusion, it is recommended to use ST_ForcePolygonCW.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Esempi

SELECT ST_AsEWKT(
  ST_ForceRHR(
        'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'
  )
);
                                                  st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))
(1 row)

Name

ST_ForceCurve — Upcast a geometry into its curved type, if applicable.

Synopsis

geometry ST_ForceCurve(geometry g);

Descrizione

Turns a geometry into its curved representation, if applicable: lines become compoundcurves, multilines become multicurves polygons become curvepolygons multipolygons become multisurfaces. If the geometry input is already a curved representation returns back same as input.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT ST_AsText(
  ST_ForceCurve(
        'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'::geometry
  )
);
                              st_astext
----------------------------------------------------------------------
 CURVEPOLYGON Z ((0 0 2,5 0 2,0 5 2,0 0 2),(1 1 2,1 3 2,3 1 2,1 1 2))
(1 row)

Si veda anche

ST_LineMerge


Name

ST_LineMerge — Converts a linear geometry to a curved geometry.

Synopsis

geometry ST_Reverse(geometry g1);

Descrizione

Converts plain LINESTRING/POLYGON to CIRCULAR STRINGs and Curved Polygons. Note much fewer points are needed to describe the curved equivalent.

[Note]

If the input LINESTRING/POLYGON is not curved enough to clearly represent a curve, the function will return the same input geometry.

Disponibilità: 1.1.0

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

-- 2D Example
SELECT ST_AsText(ST_LineToCurve(foo.the_geom)) As curvedastext,ST_AsText(foo.the_geom) As non_curvedastext
    FROM (SELECT ST_Buffer('POINT(1 3)'::geometry, 3) As the_geom) As foo;

curvedatext                                                            non_curvedastext
--------------------------------------------------------------------|-----------------------------------------------------------------
CURVEPOLYGON(CIRCULARSTRING(4 3,3.12132034355964 0.878679656440359, | POLYGON((4 3,3.94235584120969 2.41472903395162,3.77163859753386 1.85194970290473,
1 0,-1.12132034355965 5.12132034355963,4 3))                        |  3.49440883690764 1.33328930094119,3.12132034355964 0.878679656440359,
                                                                    |  2.66671069905881 0.505591163092366,2.14805029709527 0.228361402466141,
                                                                    |  1.58527096604839 0.0576441587903094,1 0,
                                                                    |  0.414729033951621 0.0576441587903077,-0.148050297095264 0.228361402466137,
                                                                    |  -0.666710699058802 0.505591163092361,-1.12132034355964 0.878679656440353,
                                                                    |  -1.49440883690763 1.33328930094119,-1.77163859753386 1.85194970290472
                                                                    |  --ETC-- ,3.94235584120969 3.58527096604839,4 3))

--3D example
SELECT ST_AsText(ST_LineToCurve(geom)) As curved, ST_AsText(geom) AS not_curved
FROM (SELECT ST_Translate(ST_Force3D(ST_Boundary(ST_Buffer(ST_Point(1,3), 2,2))),0,0,3) AS geom) AS foo;

                        curved                        |               not_curved
------------------------------------------------------+---------------------------------------------------------------------
 CIRCULARSTRING Z (3 3 3,-1 2.99999999999999 3,3 3 3) | LINESTRING Z (3 3 3,2.4142135623731 1.58578643762691 3,1 1 3,
                                                      | -0.414213562373092 1.5857864376269 3,-1 2.99999999999999 3,
                                                      | -0.414213562373101 4.41421356237309 3,
                                                      | 0.999999999999991 5 3,2.41421356237309 4.4142135623731 3,3 3 3)
(1 row)

Si veda anche

ST_CurveToLine


Name

ST_Multi — Return the geometry as a MULTI* geometry.

Synopsis

geometry ST_Multi(geometry g1);

Descrizione

Returns the geometry as a MULTI* geometry collection. If the geometry is already a collection, it is returned unchanged.

Esempi

SELECT ST_AsEWKT(
  ST_ForceRHR(
        'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'
  )
);
                                                  st_asewkt
--------------------------------------------------------------
 POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))
(1 row)

Si veda anche

ST_AsText


Name

ST_Normalize — Return the geometry in its canonical form.

Synopsis

geometry ST_Normalize(geometry geom);

Descrizione

Returns the geometry in its normalized/canonical form. May reorder vertices in polygon rings, rings in a polygon, elements in a multi-geometry complex.

Mostly only useful for testing purposes (comparing expected and obtained results).

Availability: 2.3.0

Esempi

SELECT ST_AsText(ST_Normalize(ST_GeomFromText(
  'GEOMETRYCOLLECTION(
    POINT(2 3),
    MULTILINESTRING((0 0, 1 1),(2 2, 3 3)),
    POLYGON(
      (0 10,0 0,10 0,10 10,0 10),
      (4 2,2 2,2 4,4 4,4 2),
      (6 8,8 8,8 6,6 6,6 8)
    )
  )'
)));
                                                                     st_astext
----------------------------------------------------------------------------------------------------------------------------------------------------
 GEOMETRYCOLLECTION(POLYGON((0 0,0 10,10 10,10 0,0 0),(6 6,8 6,8 8,6 8,6 6),(2 2,4 2,4 4,2 4,2 2)),MULTILINESTRING((2 2,3 3),(0 0,1 1)),POINT(2 3))
(1 row)
                        

Si veda anche

ST_Equals,


Name

ST_QuantizeCoordinates — Sets least significant bits of coordinates to zero

Synopsis

geometry ST_TransScale(geometry geomA, float deltaX, float deltaY, float XFactor, float YFactor);

Descrizione

ST_QuantizeCoordinates determines the number of bits (N) required to represent a coordinate value with a specified number of digits after the decimal point, and then sets all but the N most significant bits to zero. The resulting coordinate value will still round to the original value, but will have improved compressiblity. This can result in a significant disk usage reduction provided that the geometry column is using a compressible storage type. The function allows specification of a different number of digits after the decimal point in each dimension; unspecified dimensions are assumed to have the precsion of the x dimension. Negative digits are interpreted to refer digits to the left of the decimal point, (i.e., prec_x=-2 will preserve coordinate values to the nearest 100.

The coordinates produced by ST_QuantizeCoordinates are independent of the geometry that contains those coordinates and the relative position of those coordinates within the geometry. As a result, existing topological relationships between geometries are unaffected by use of this function. The function may produce invalid geometry when it is called with a number of digits lower than the intrinsic precision of the geometry.

Disponibilità: 2.0

Technical Background

PostGIS stores all coordinate values as double-precision floating point integers, which can reliably represent 15 significant digits. However, PostGIS may be used to manage data that intrinsically has fewer than 15 significant digits. An example is TIGER data, which is provided as geographic coordinates with six digits of precision after the decimal point (thus requiring only nine significant digits of longitude and eight significant digits of latitude.)

When 15 significant digits are available, there are many possible representations of a number with 9 significant digits. A double precision floating point number uses 52 explicit bits to represent the significand (mantissa) of the coordinate. Only 30 bits are needed to represent a mantissa with 9 significant digits, leaving 22 insignificant bits; we can set their value to anything we like and still end up with a number that rounds to our input value. For example, the value 100.123456 can be represented by the floating point numbers closest to 100.123456000000, 100.123456000001, and 100.123456432199. All are equally valid, in that ST_AsText(geom, 6) will return the same result with any of these inputs. As we can set these bits to any value, ST_QuantizeCoordinates sets the 22 insignificant bits to zero. For a long coordinate sequence this creates a pattern of blocks of consecutive zeros that is compressed by PostgreSQL more effeciently.

[Note]

Only the on-disk size of the geometry is potentially affected by ST_QuantizeCoordinates. ST_MemSize, which reports the in-memory usage of the geometry, will return the the same value regardless of the disk space used by a geometry.

Esempi

SELECT ST_AsText(ST_QuantizeCoordinates('POINT (100.123456 0)'::geometry, 4));
st_astext
-------------------------
POINT(100.123455047607 0)
                        
WITH test AS (SELECT 'POINT (123.456789123456 123.456789123456)'::geometry AS geom)
SELECT
  digits,
  encode(ST_QuantizeCoordinates(geom, digits), 'hex'),
  ST_AsText(ST_QuantizeCoordinates(geom, digits))
FROM test, generate_series(15, -15, -1) AS digits;

digits  |                   encode                   |                st_astext
--------+--------------------------------------------+------------------------------------------
15      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
14      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
13      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
12      | 01010000005c9a72083cdd5e405c9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
11      | 0101000000409a72083cdd5e40409a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
10      | 0101000000009a72083cdd5e40009a72083cdd5e40 | POINT(123.456789123455 123.456789123455)
9       | 0101000000009072083cdd5e40009072083cdd5e40 | POINT(123.456789123418 123.456789123418)
8       | 0101000000008072083cdd5e40008072083cdd5e40 | POINT(123.45678912336 123.45678912336)
7       | 0101000000000070083cdd5e40000070083cdd5e40 | POINT(123.456789121032 123.456789121032)
6       | 0101000000000040083cdd5e40000040083cdd5e40 | POINT(123.456789076328 123.456789076328)
5       | 0101000000000000083cdd5e40000000083cdd5e40 | POINT(123.456789016724 123.456789016724)
4       | 0101000000000000003cdd5e40000000003cdd5e40 | POINT(123.456787109375 123.456787109375)
3       | 0101000000000000003cdd5e40000000003cdd5e40 | POINT(123.456787109375 123.456787109375)
2       | 01010000000000000038dd5e400000000038dd5e40 | POINT(123.45654296875 123.45654296875)
1       | 01010000000000000000dd5e400000000000dd5e40 | POINT(123.453125 123.453125)
0       | 01010000000000000000dc5e400000000000dc5e40 | POINT(123.4375 123.4375)
-1      | 01010000000000000000c05e400000000000c05e40 | POINT(123 123)
-2      | 01010000000000000000005e400000000000005e40 | POINT(120 120)
-3      | 010100000000000000000058400000000000005840 | POINT(96 96)
-4      | 010100000000000000000058400000000000005840 | POINT(96 96)
-5      | 010100000000000000000058400000000000005840 | POINT(96 96)
-6      | 010100000000000000000058400000000000005840 | POINT(96 96)
-7      | 010100000000000000000058400000000000005840 | POINT(96 96)
-8      | 010100000000000000000058400000000000005840 | POINT(96 96)
-9      | 010100000000000000000058400000000000005840 | POINT(96 96)
-10     | 010100000000000000000058400000000000005840 | POINT(96 96)
-11     | 010100000000000000000058400000000000005840 | POINT(96 96)
-12     | 010100000000000000000058400000000000005840 | POINT(96 96)
-13     | 010100000000000000000058400000000000005840 | POINT(96 96)
-14     | 010100000000000000000058400000000000005840 | POINT(96 96)
-15     | 010100000000000000000058400000000000005840 | POINT(96 96)

Si veda anche

ST_SnapToGrid


Name

ST_RemovePoint — Remove a point from a linestring.

Synopsis

geometry ST_RemovePoint(geometry linestring, integer offset);

Descrizione

Removes a point from a LineString, given its index (0-based). Useful for turning a closed line (ring) into an open linestring.

Disponibilità: 1.1.0

This function supports 3d and will not drop the z-index.

Esempi

Guarantees no lines are closed by removing the end point of closed lines (rings). Assumes geom is of type LINESTRING

UPDATE sometable
        SET geom = ST_RemovePoint(geom, ST_NPoints(geom) - 1)
        FROM sometable
        WHERE ST_IsClosed(geom);

Name

ST_RemovePoint — Returns a version of the given geometry with duplicated points removed.

Synopsis

geometry ST_RotateY(geometry geomA, float rotRadians);

Descrizione

Returns a version of the given geometry with duplicated points removed. Will actually do something only with (multi)lines, (multi)polygons and multipoints but you can safely call it with any kind of geometry. Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.

If the tolerance parameter is provided, vertices within the tolerance of one another will be considered the "same" for the purposes of removal.

Availability: 2.2.0

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

Si veda anche

ST_Simplify


Name

ST_Reverse — Return the geometry with vertex order reversed.

Synopsis

geometry ST_Reverse(geometry g1);

Descrizione

Can be used on any geometry and reverses the order of the vertexes.

Enhanced: 2.4.0 support for curves was introduced.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Esempi

SELECT ST_AsText(the_geom) as line, ST_AsText(ST_Reverse(the_geom)) As reverseline
FROM
(SELECT ST_MakeLine(ST_MakePoint(1,2),
                ST_MakePoint(1,10)) As the_geom) as foo;
--result
                line         |     reverseline
---------------------+----------------------
LINESTRING(1 2,1 10) | LINESTRING(1 10,1 2)

Name

ST_Segmentize — Return a modified geometry/geography having no segment longer than the given distance.

Synopsis

geometry ST_Segmentize(geometry geom, float max_segment_length);

geography ST_Segmentize(geography geog, float max_segment_length);

Descrizione

Returns a modified geometry having no segment longer than the given max_segment_length. Distance computation is performed in 2d only. For geometry, length units are in units of spatial reference. For geography, units are in meters.

Availability: 1.2.2

Enhanced: 3.0.0 Segmentize geometry now uses equal length segments

Enhanced: 2.3.0 Segmentize geography now uses equal length segments

Enhanced: 2.1.0 support for geography was introduced.

Changed: 2.1.0 As a result of the introduction of geography support: The construct SELECT ST_Segmentize('LINESTRING(1 2, 3 4)',0.5); will result in ambiguous function error. You need to have properly typed object e.g. a geometry/geography column, use ST_GeomFromText, ST_GeogFromText or SELECT ST_Segmentize('LINESTRING(1 2, 3 4)'::geometry,0.5);

[Note]

This will only increase segments. It will not lengthen segments shorter than max length

Esempi

SELECT ST_AsText(ST_Segmentize(
ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
                ,5)
);
st_astext
--------------------------------------------------------------------------------------------------
MULTILINESTRING((-29 -27,-30 -29.7,-34.886615700134 -30.758766735029,-36 -31,
-40.8809353009198 -32.0846522890933,-45 -33),
(-45 -33,-46 -32))
(1 row)

SELECT ST_AsText(ST_Segmentize(ST_GeomFromText('POLYGON((-29 28, -30 40, -29 28))'),10));
st_astext
-----------------------
POLYGON((-29 28,-29.8304547985374 37.9654575824488,-30 40,-29.1695452014626 30.0345424175512,-29 28))
(1 row)

                        

Si veda anche

ST_LineSubstring


Name

ST_SetPoint — Replace point of a linestring with a given point.

Synopsis

geometry ST_SetPoint(geometry linestring, integer zerobasedposition, geometry point);

Descrizione

Replace point N of linestring with given point. Index is 0-based.Negative index are counted backwards, so that -1 is last point. This is especially useful in triggers when trying to maintain relationship of joints when one vertex moves.

Disponibilità: 1.1.0

Updated 2.3.0 : negative indexing

This function supports 3d and will not drop the z-index.

Esempi

--Change first point in line string from -1 3 to -1 1
SELECT ST_AsText(ST_SetPoint('LINESTRING(-1 2,-1 3)', 0, 'POINT(-1 1)'));
           st_astext
-----------------------
 LINESTRING(-1 1,-1 3)

---Change last point in a line string (lets play with 3d linestring this time)
SELECT ST_AsEWKT(ST_SetPoint(foo.the_geom, ST_NumPoints(foo.the_geom) - 1, ST_GeomFromEWKT('POINT(-1 1 3)')))
FROM (SELECT ST_GeomFromEWKT('LINESTRING(-1 2 3,-1 3 4, 5 6 7)') As the_geom) As foo;
           st_asewkt
-----------------------
LINESTRING(-1 2 3,-1 3 4,-1 1 3)

SELECT ST_AsText(ST_SetPoint(g, -3, p))
FROM ST_GEomFromText('LINESTRING(0 0, 1 1, 2 2, 3 3, 4 4)') AS g
        , ST_PointN(g,1) as p;
           st_astext
-----------------------
LINESTRING(0 0,1 1,0 0,3 3,4 4)

                        

Name

ST_ShiftLongitude — Shifts a geometry with geographic coordinates between -180..180 and 0..360.

Synopsis

geometry ST_Multi(geometry g1);

Descrizione

Reads every point/vertex in a geometry, and if the longitude coordinate is <0, adds 360 to it. The result is a 0-360 version of the data to be plotted in a 180 centric map

[Note]

This is only useful for data with coordinates in longitude/latitude; e.g. SRID 4326 (WGS 84 geographic)

[Warning]

Pre-1.3.4 bug prevented this from working for MULTIPOINT. 1.3.4+ works with MULTIPOINT as well.

This function supports 3d and will not drop the z-index.

Miglioramento: nella versione 2.0.0 è stato introdotto il supporto per le superfici poliedriche.

NOTE: this function was renamed from "ST_Shift_Longitude" in 2.2.0

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

--3d points
SELECT ST_AsEWKT(ST_ShiftLongitude(ST_GeomFromEWKT('SRID=4326;POINT(-118.58 38.38 10)'))) As geomA,
    ST_AsEWKT(ST_ShiftLongitude(ST_GeomFromEWKT('SRID=4326;POINT(241.42 38.38 10)'))) As geomb
geomA                             geomB
----------                        -----------
SRID=4326;POINT(241.42 38.38 10) SRID=4326;POINT(-118.58 38.38 10)

--regular line string
SELECT ST_AsText(ST_ShiftLongitude(ST_GeomFromText('LINESTRING(-118.58 38.38, -118.20 38.45)')))

st_astext
----------
LINESTRING(241.42 38.38,241.8 38.45)
        

Si veda anche

ST_WrapX


Name

ST_WrapX — Wrap a geometry around an X value.

Synopsis

geometry ST_Snap(geometry input, geometry reference, float tolerance);

Descrizione

This function splits the input geometries and then moves every resulting component falling on the right (for negative 'move') or on the left (for positive 'move') of given 'wrap' line in the direction specified by the 'move' parameter, finally re-unioning the pieces togheter.

[Note]

This is useful to "recenter" long-lat input to have features of interest not spawned from one side to the other.

Disponibilità: 2.0

This function supports 3d and will not drop the z-index.

Esempi

-- Move all components of the given geometries whose bounding box
-- falls completely on the left of x=0 to +360
select ST_WrapX(the_geom, 0, 360);

-- Move all components of the given geometries whose bounding box
-- falls completely on the left of x=-30 to +360
select ST_WrapX(the_geom, -30, 360);
        

Si veda anche

ST_ShiftLongitude


Name

ST_SnapToGrid — Snap all points of the input geometry to a regular grid.

Synopsis

geometry ST_SnapToGrid(geometry geomA, float originX, float originY, float sizeX, float sizeY);

geometry ST_SnapToGrid(geometry geomA, float sizeX, float sizeY);

geometry ST_SnapToGrid(geometry geomA, float size);

geometry ST_SnapToGrid(geometry geomA, geometry pointOrigin, float sizeX, float sizeY, float sizeZ, float sizeM);

Descrizione

Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive points falling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type. Collapsed geometries in a collection are stripped from it. Useful for reducing precision.

Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, must be a point) and cell sizes. Specify 0 as size for any dimension you don't want to snap to a grid.

[Note]

The returned geometry might lose its simplicity (see ST_IsSimple).

[Note]

Before release 1.1.0 this function always returned a 2d geometry. Starting at 1.1.0 the returned geometry will have same dimensionality as the input one with higher dimension values untouched. Use the version taking a second geometry argument to define all grid dimensions.

Disponibilità: dalla versione 1.0.0RC1

Availability: 1.1.0 - Z and M support

This function supports 3d and will not drop the z-index.

Esempi

--Snap your geometries to a precision grid of 10^-3
UPDATE mytable
   SET the_geom = ST_SnapToGrid(the_geom, 0.001);

SELECT ST_AsText(ST_SnapToGrid(
                        ST_GeomFromText('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'),
                        0.001)
                );
                          st_astext
-------------------------------------
 LINESTRING(1.112 2.123,4.111 3.237)
 --Snap a 4d geometry
SELECT ST_AsEWKT(ST_SnapToGrid(
        ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 2.3456 1.11111,
                4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)'),
 ST_GeomFromEWKT('POINT(1.12 2.22 3.2 4.4444)'),
 0.1, 0.1, 0.1, 0.01) );
                                                                  st_asewkt
------------------------------------------------------------------------------
 LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)


--With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m and z the same
SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 3 2.3456,
                4.111111 3.2374897 3.1234 1.1111)'),
           0.01)      );
                                                st_asewkt
---------------------------------------------------------
 LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)

                

Name

ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.

Synopsis

geometry ST_Snap(geometry input, geometry reference, float tolerance);

Descrizione

Snaps the vertices and segments of a geometry to another Geometry's vertices. A snap distance tolerance is used to control where snapping is performed. The result geometry is the input geometry with the vertices snapped. If no snapping occurs then the input geometry is returned unchanged.

Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (which cause problems during noding and intersection calculation).

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided using heuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.

[Note]

The returned geometry might lose its simplicity (see ST_IsSimple) and validity (see ST_IsValid).

Performed by the GEOS module.

Disponibilità: 2.0

Esempi

A multipolygon shown with a linestring (before any snapping)

A multipolygon snapped to linestring to tolerance: 1.01 of distance. The new multipolygon is shown with reference linestring

SELECT ST_AsText(ST_Snap(poly,line, ST_Distance(poly,line)*1.01)) AS polysnapped
FROM (SELECT
   ST_GeomFromText('MULTIPOLYGON(
     ((26 125, 26 200, 126 200, 126 125, 26 125 ),
      ( 51 150, 101 150, 76 175, 51 150 )),
      (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
        ) As foo;

                             polysnapped
---------------------------------------------------------------------
 MULTIPOLYGON(((26 125,26 200,126 200,126 125,101 100,26 125),
 (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
                                

A multipolygon snapped to linestring to tolerance: 1.25 of distance. The new multipolygon is shown with reference linestring

SELECT ST_AsText(
    ST_Snap(poly,line, ST_Distance(poly,line)*1.25)
  ) AS polysnapped
FROM (SELECT
  ST_GeomFromText('MULTIPOLYGON(
    (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
      ( 51 150, 101 150, 76 175, 51 150 )),
      (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
        ) As foo;

                             polysnapped
---------------------------------------------------------------------
MULTIPOLYGON(((5 107,26 200,126 200,126 125,101 100,54 84,5 107),
(51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
                                

The linestring snapped to the original multipolygon at tolerance 1.01 of distance. The new linestring is shown with reference multipolygon

SELECT ST_AsText(
   ST_Snap(line, poly, ST_Distance(poly,line)*1.01)
  ) AS linesnapped
FROM (SELECT
  ST_GeomFromText('MULTIPOLYGON(
     ((26 125, 26 200, 126 200, 126 125, 26 125),
      (51 150, 101 150, 76 175, 51 150 )),
      ((151 100, 151 200, 176 175, 151 100)))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
        ) As foo;

              linesnapped
----------------------------------------
 LINESTRING(5 107,26 125,54 84,101 100)
                                

The linestring snapped to the original multipolygon at tolerance 1.25 of distance. The new linestring is shown with reference multipolygon

SELECT ST_AsText(
 ST_Snap(line, poly, ST_Distance(poly,line)*1.25)
  ) AS linesnapped
FROM (SELECT
  ST_GeomFromText('MULTIPOLYGON(
     (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
      (51 150, 101 150, 76 175, 51 150 )),
      ((151 100, 151 200, 176 175, 151 100 )))') As poly,
       ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
        ) As foo;
              linesnapped
---------------------------------------
LINESTRING(26 125,54 84,101 100)
                                

Si veda anche

ST_SnapToGrid


Name

ST_SwapOrdinates — Returns a version of the given geometry with given ordinate values swapped.

Synopsis

geometry ST_SetSRID(geometry geom, integer srid);

Descrizione

Returns a version of the given geometry with given ordinates swapped.

The ords parameter is a 2-characters string naming the ordinates to swap. Valid names are: x,y,z and m.

Availability: 2.2.0

This method supports Circular Strings and Curves

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

-- Scale M value by 2
SELECT ST_AsText(
  ST_SwapOrdinates(
    ST_Scale(
      ST_SwapOrdinates(g,'xm'),
      2, 1
    ),
  'xm')
) FROM ( SELECT 'POINT ZM (0 0 0 2)'::geometry g ) foo;
     st_astext
--------------------
 POINT ZM (0 0 0 4)
                 

Si veda anche

ST_FlipCoordinates

8.6. Geometry Validation

Abstract

These functions test whether geometries are valid according to the OGC SFS standard. They also provide information about the nature and location of invalidity. There is also a function to create a valid geometry out of an invalid one.

ST_IsValid — Tests if a geometry is well-formed in 2D.
ST_IsValidDetail — Returns a valid_detail row stating if a geometry is valid or if not a reason and a location.
ST_IsValidReason — Returns text stating if a geometry is valid, or a reason for invalidity.
ST_MakeValid — Attempts to make an invalid geometry valid without losing vertices.

Name

ST_IsValid — Tests if a geometry is well-formed in 2D.

Synopsis

boolean ST_IsValid(geometry g);

boolean ST_IsValid(geometry g, integer flags);

Description

Tests if an ST_Geometry value is well-formed and valid in 2D according to the OGC rules. For geometries with 3 and 4 dimensions, the validity is still only tested in 2 dimensions. For geometries that are invalid, a PostgreSQL NOTICE is emitted providing details of why it is not valid.

For the version with the flags parameter, supported values are documented in ST_IsValidDetail This version does not print a NOTICE explaining invalidity.

For more information on the definition of geometry validity, refer to Section 4.6, “Geometry Validation”

[Note]

SQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL.

Performed by the GEOS module.

The version accepting flags is available starting with 2.0.0.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.9

[Note]

Neither OGC-SFS nor SQL-MM specifications include a flag argument for ST_IsValid. The flag is a PostGIS extension.

Examples

SELECT ST_IsValid(ST_GeomFromText('LINESTRING(0 0, 1 1)')) As good_line,
        ST_IsValid(ST_GeomFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) As bad_poly
--results
NOTICE:  Self-intersection at or near point 0 0
 good_line | bad_poly
-----------+----------
 t         | f

Name

ST_IsValidDetail — Returns a valid_detail row stating if a geometry is valid or if not a reason and a location.

Synopsis

valid_detail ST_IsValidDetail(geometry geom, integer flags);

Description

Returns a valid_detail row, containing a boolean (valid) stating if a geometry is valid, a varchar (reason) stating a reason why it is invalid and a geometry (location) pointing out where it is invalid.

Useful to improve on the combination of ST_IsValid and ST_IsValidReason to generate a detailed report of invalid geometries.

The optional flags parameter is a bitfield. It can have the following values:

  • 0: Use usual OGC SFS validity semantics.

  • 1: Consider certain kinds of self-touching rings (inverted shells and exverted holes) as valid. This is also known as "the ESRI flag", since this is the validity model used by those tools. Note that this is invalid under the OGC model.

Performed by the GEOS module.

Availability: 2.0.0

Examples

--First 3 Rejects from a successful quintuplet experiment
SELECT gid, reason(ST_IsValidDetail(the_geom)), ST_AsText(location(ST_IsValidDetail(the_geom))) as location
FROM
(SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), array_agg(f.line)) As the_geom, gid
FROM (SELECT ST_Buffer(ST_Point(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
        FROM generate_series(-4,6) x1
        CROSS JOIN generate_series(2,5) y1
        CROSS JOIN generate_series(1,8) z1
        WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
        INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_Point(x1*10,y1), z1)),y1*1, z1*2) As line
        FROM generate_series(-3,6) x1
        CROSS JOIN generate_series(2,5) y1
        CROSS JOIN generate_series(1,10) z1
        WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
GROUP BY gid, e.buff) As quintuplet_experiment
WHERE ST_IsValid(the_geom) = false
ORDER BY gid
LIMIT 3;

 gid  |      reason       |  location
------+-------------------+-------------
 5330 | Self-intersection | POINT(32 5)
 5340 | Self-intersection | POINT(42 5)
 5350 | Self-intersection | POINT(52 5)

 --simple example
SELECT * FROM ST_IsValidDetail('LINESTRING(220227 150406,2220227 150407,222020 150410)');

 valid | reason | location
-------+--------+----------
 t     |        |

                

Name

ST_IsValidReason — Returns text stating if a geometry is valid, or a reason for invalidity.

Synopsis

text ST_IsValidReason(geometry geomA);

text ST_IsValidReason(geometry geomA, integer flags);

Description

Returns text stating if a geometry is valid, or if invalid a reason why.

Useful in combination with ST_IsValid to generate a detailed report of invalid geometries and reasons.

Allowed flags are documented in ST_IsValidDetail.

Performed by the GEOS module.

Availability: 1.4

Availability: 2.0 version taking flags.

Examples

-- invalid bow-tie polygon
SELECT ST_IsValidReason(
    'POLYGON ((100 200, 100 100, 200 200,
     200 100, 100 200))'::geometry) as validity_info;
validity_info
--------------------------
Self-intersection[150 150]
        
--First 3 Rejects from a successful quintuplet experiment
SELECT gid, ST_IsValidReason(the_geom) as validity_info
FROM
(SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), array_agg(f.line)) As the_geom, gid
FROM (SELECT ST_Buffer(ST_Point(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
        FROM generate_series(-4,6) x1
        CROSS JOIN generate_series(2,5) y1
        CROSS JOIN generate_series(1,8) z1
        WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
        INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_Point(x1*10,y1), z1)),y1*1, z1*2) As line
        FROM generate_series(-3,6) x1
        CROSS JOIN generate_series(2,5) y1
        CROSS JOIN generate_series(1,10) z1
        WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
GROUP BY gid, e.buff) As quintuplet_experiment
WHERE ST_IsValid(the_geom) = false
ORDER BY gid
LIMIT 3;

 gid  |      validity_info
------+--------------------------
 5330 | Self-intersection [32 5]
 5340 | Self-intersection [42 5]
 5350 | Self-intersection [52 5]

 --simple example
SELECT ST_IsValidReason('LINESTRING(220227 150406,2220227 150407,222020 150410)');

 st_isvalidreason
------------------
 Valid Geometry

                

Name

ST_MakeValid — Attempts to make an invalid geometry valid without losing vertices.

Synopsis

geometry ST_MakeValid(geometry input);

geometry ST_MakeValid(geometry input, text params);

Description

The function attempts to create a valid representation of a given invalid geometry without losing any of the input vertices. Valid geometries are returned unchanged.

Supported inputs are: POINTS, MULTIPOINTS, LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS and GEOMETRYCOLLECTIONS containing any mix of them.

In case of full or partial dimensional collapses, the output geometry may be a collection of lower-to-equal dimension geometries, or a geometry of lower dimension.

Single polygons may become multi-geometries in case of self-intersections.

The params argument can be used to supply an options string to select the method to use for building valid geometry. The options string is in the format "method=linework|structure keepcollapsed=true|false".

The "method" key has two values.

  • "linework" is the original algorithm, and builds valid geometries by first extracting all lines, noding that linework together, then building a value output from the linework.

  • "structure" is an algorithm that distinguishes between interior and exterior rings, building new geometry by unioning exterior rings, and then differencing all interior rings.

The "keepcollapsed" key is only valid for the "structure" algorithm, and takes a value of "true" or "false". When set to "false", geometry components that collapse to a lower dimensionality, for example a one-point linestring would be dropped.

Performed by the GEOS module.

Availability: 2.0.0

Enhanced: 2.0.1, speed improvements

Enhanced: 2.1.0, added support for GEOMETRYCOLLECTION and MULTIPOINT.

Enhanced: 3.1.0, added removal of Coordinates with NaN values.

Enhanced: 3.2.0, added algorithm options, 'linework' and 'structure'.

This function supports 3d and will not drop the z-index.

Examples

before_geom: MULTIPOLYGON of 2 overlapping polygons

after_geom: MULTIPOLYGON of 4 non-overlapping polygons

after_geom_structure: MULTIPOLYGON of 1 non-overlapping polygon

SELECT f.geom AS before_geom, ST_MakeValid(f.geom) AS after_geom, ST_MakeValid(f.geom, 'method=structure') AS after_geom_structure
FROM (SELECT 'MULTIPOLYGON(((186 194,187 194,188 195,189 195,190 195,
191 195,192 195,193 194,194 194,194 193,195 192,195 191,
195 190,195 189,195 188,194 187,194 186,14 6,13 6,12 5,11 5,
10 5,9 5,8 5,7 6,6 6,6 7,5 8,5 9,5 10,5 11,5 12,6 13,6 14,186 194)),
((150 90,149 80,146 71,142 62,135 55,128 48,119 44,110 41,100 40,
90 41,81 44,72 48,65 55,58 62,54 71,51 80,50 90,51 100,
54 109,58 118,65 125,72 132,81 136,90 139,100 140,110 139,
119 136,128 132,135 125,142 118,146 109,149 100,150 90)))'::geometry AS geom) AS f;

before_geom: MULTIPOLYGON of 6 overlapping polygons

after_geom: MULTIPOLYGON of 14 Non-overlapping polygons

after_geom_structure: MULTIPOLYGON of 1 Non-overlapping polygon

SELECT c.geom AS before_geom,
                    ST_MakeValid(c.geom) AS after_geom,
                    ST_MakeValid(c.geom, 'method=structure') AS after_geom_structure
        FROM (SELECT 'MULTIPOLYGON(((91 50,79 22,51 10,23 22,11 50,23 78,51 90,79 78,91 50)),
                  ((91 100,79 72,51 60,23 72,11 100,23 128,51 140,79 128,91 100)),
                  ((91 150,79 122,51 110,23 122,11 150,23 178,51 190,79 178,91 150)),
                  ((141 50,129 22,101 10,73 22,61 50,73 78,101 90,129 78,141 50)),
                  ((141 100,129 72,101 60,73 72,61 100,73 128,101 140,129 128,141 100)),
                  ((141 150,129 122,101 110,73 122,61 150,73 178,101 190,129 178,141 150)))'::geometry AS geom) AS c;

Examples

SELECT ST_AsText(ST_MakeValid(
    'LINESTRING(0 0, 0 0)',
    'method=structure keepcollapsed=true'
    ));

 st_astext
------------
 POINT(0 0)


SELECT ST_AsText(ST_MakeValid(
    'LINESTRING(0 0, 0 0)',
    'method=structure keepcollapsed=false'
    ));

    st_astext
------------------
 LINESTRING EMPTY

8.7. Spatial Reference System Functions

Abstract

These functions work with the Spatial Reference System of geometries as defined in the spatial_ref_sys table.

ST_SetSRID — Set the SRID on a geometry.
ST_SRID — Returns the spatial reference identifier for a geometry.
ST_Transform — Return a new geometry with coordinates transformed to a different spatial reference system.

Name

ST_SetSRID — Set the SRID on a geometry.

Synopsis

geometry ST_SetSRID(geometry geom, integer srid);

Description

Sets the SRID on a geometry to a particular integer value. Useful in constructing bounding boxes for queries.

[Note]

This function does not transform the geometry coordinates in any way - it simply sets the meta data defining the spatial reference system the geometry is assumed to be in. Use ST_Transform if you want to transform the geometry into a new projection.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves

Examples

-- Mark a point as WGS 84 long lat --

SELECT ST_SetSRID(ST_Point(-123.365556, 48.428611),4326) As wgs84long_lat;
-- the ewkt representation (wrap with ST_AsEWKT) -
SRID=4326;POINT(-123.365556 48.428611)
                        

-- Mark a point as WGS 84 long lat and then transform to web mercator (Spherical Mercator) --

SELECT ST_Transform(ST_SetSRID(ST_Point(-123.365556, 48.428611),4326),3785) As spere_merc;
-- the ewkt representation (wrap with ST_AsEWKT) -
SRID=3785;POINT(-13732990.8753491 6178458.96425423)
                        

Name

ST_SRID — Returns the spatial reference identifier for a geometry.

Synopsis

integer ST_SRID(geometry g1);

Description

Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. Section 4.5, “Spatial Reference Systems”

[Note]

spatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformations from one spatial reference system to another. So verifying you have the right spatial reference system identifier is important if you plan to ever transform your geometries.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.5

This method supports Circular Strings and Curves

Examples

SELECT ST_SRID(ST_GeomFromText('POINT(-71.1043 42.315)',4326));
                --result
                4326
                

Name

ST_Transform — Return a new geometry with coordinates transformed to a different spatial reference system.

Synopsis

geometry ST_Transform(geometry g1, integer srid);

geometry ST_Transform(geometry geom, text to_proj);

geometry ST_Transform(geometry geom, text from_proj, text to_proj);

geometry ST_Transform(geometry geom, text from_proj, integer to_srid);

Description

Returns a new geometry with its coordinates transformed to a different spatial reference system. The destination spatial reference to_srid may be identified by a valid SRID integer parameter (i.e. it must exist in the spatial_ref_sys table). Alternatively, a spatial reference defined as a PROJ.4 string can be used for to_proj and/or from_proj, however these methods are not optimized. If the destination spatial reference system is expressed with a PROJ.4 string instead of an SRID, the SRID of the output geometry will be set to zero. With the exception of functions with from_proj, input geometries must have a defined SRID.

ST_Transform is often confused with ST_SetSRID. ST_Transform actually changes the coordinates of a geometry from one spatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the geometry.

[Note]

Requires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiled in.

[Note]

If using more than one transformation, it is useful to have a functional index on the commonly used transformations to take advantage of index usage.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Enhanced: 2.3.0 support for direct PROJ.4 text was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.6

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Examples

Change Massachusetts state plane US feet geometry to WGS 84 long lat

SELECT ST_AsText(ST_Transform(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
        743265 2967450,743265.625 2967416,743238 2967416))',2249),4326)) As wgs_geom;

 wgs_geom
---------------------------
 POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
-71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.177684
8522251 42.3902896512902));
(1 row)

--3D Circular String example
SELECT ST_AsEWKT(ST_Transform(ST_GeomFromEWKT('SRID=2249;CIRCULARSTRING(743238 2967416 1,743238 2967450 2,743265 2967450 3,743265.625 2967416 3,743238 2967416 4)'),4326));

                                 st_asewkt
--------------------------------------------------------------------------------------
 SRID=4326;CIRCULARSTRING(-71.1776848522251 42.3902896512902 1,-71.1776843766326 42.3903829478009 2,
 -71.1775844305465 42.3903826677917 3,
 -71.1775825927231 42.3902893647987 3,-71.1776848522251 42.3902896512902 4)

                

Example of creating a partial functional index. For tables where you are not sure all the geometries will be filled in, its best to use a partial index that leaves out null geometries which will both conserve space and make your index smaller and more efficient.

CREATE INDEX idx_the_geom_26986_parcels
  ON parcels
  USING gist
  (ST_Transform(the_geom, 26986))
  WHERE the_geom IS NOT NULL;
                

Examples of using PROJ.4 text to transform with custom spatial references.

-- Find intersection of two polygons near the North pole, using a custom Gnomic projection
-- See http://boundlessgeo.com/2012/02/flattening-the-peel/
 WITH data AS (
   SELECT
     ST_GeomFromText('POLYGON((170 50,170 72,-130 72,-130 50,170 50))', 4326) AS p1,
     ST_GeomFromText('POLYGON((-170 68,-170 90,-141 90,-141 68,-170 68))', 4326) AS p2,
     '+proj=gnom +ellps=WGS84 +lat_0=70 +lon_0=-160 +no_defs'::text AS gnom
 )
 SELECT ST_AsText(
   ST_Transform(
     ST_Intersection(ST_Transform(p1, gnom), ST_Transform(p2, gnom)),
   gnom, 4326))
 FROM data;
                                          st_astext
 --------------------------------------------------------------------------------
  POLYGON((-170 74.053793645338,-141 73.4268621378904,-141 68,-170 68,-170 74.053793645338))
                

Configuring transformation behaviour

Sometimes coordinate transformation involving a grid-shift can fail, for example if PROJ.4 has not been built with grid-shift files or the coordinate does not lie within the range for which the grid shift is defined. By default, PostGIS will throw an error if a grid shift file is not present, but this behaviour can be configured on a per-SRID basis either by testing different to_proj values of PROJ.4 text, or altering the proj4text value within the spatial_ref_sys table.

For example, the proj4text parameter +datum=NAD87 is a shorthand form for the following +nadgrids parameter:

+nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat

The @ prefix means no error is reported if the files are not present, but if the end of the list is reached with no file having been appropriate (ie. found and overlapping) then an error is issued.

If, conversely, you wanted to ensure that at least the standard files were present, but that if all files were scanned without a hit a null transformation is applied you could use:

+nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null

The null grid shift file is a valid grid shift file covering the whole world and applying no shift. So for a complete example, if you wanted to alter PostGIS so that transformations to SRID 4267 that didn't lie within the correct range did not throw an ERROR, you would use the following:

UPDATE spatial_ref_sys SET proj4text = '+proj=longlat +ellps=clrk66 +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null +no_defs' WHERE srid = 4267;

8.8. Geometry Input

Abstract

These functions create geometry objects from various textual or binary formats.

8.8.1. Well-Known Text (WKT)

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.
ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString text representation Well-Known text representation.
ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).
ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).
ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText
ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).
ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to 0.
ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.
ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.
ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

Name

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

Synopsis

geometry ST_BdPolyFromText(text WKT, integer srid);

Description

Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

[Note]

Throws an error if WKT is not a MULTILINESTRING. Throws an error if output is a MULTIPOLYGON; use ST_BdMPolyFromText in that case, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Performed by the GEOS module.

Availability: 1.1.0


Name

ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString text representation Well-Known text representation.

Synopsis

geometry ST_BdMPolyFromText(text WKT, integer srid);

Description

Construct a Polygon given an arbitrary collection of closed linestrings, polygons, MultiLineStrings as Well-Known text representation.

[Note]

Throws an error if WKT is not a MULTILINESTRING. Forces MULTIPOLYGON output even when result is really only composed by a single POLYGON; use ST_BdPolyFromText if you're sure a single POLYGON will result from operation, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Performed by the GEOS module.

Availability: 1.1.0


Name

ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

Synopsis

geography ST_GeogFromText(text EWKT);

Description

Returns a geography object from the well-known text or extended well-known representation. SRID 4326 is assumed if unspecified. This is an alias for ST_GeographyFromText. Points are always expressed in long lat form.

Examples

--- converting lon lat coords to geography
ALTER TABLE sometable ADD COLUMN geog geography(POINT,4326);
UPDATE sometable SET geog = ST_GeogFromText('SRID=4326;POINT(' || lon || ' ' || lat || ')');

--- specify a geography point using EPSG:4267, NAD27
SELECT ST_AsEWKT(ST_GeogFromText('SRID=4267;POINT(-77.0092 38.889588)'));
                        

Name

ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

Synopsis

geography ST_GeographyFromText(text EWKT);

Description

Returns a geography object from the well-known text representation. SRID 4326 is assumed if unspecified.


Name

ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_GeomCollFromText(text WKT, integer srid);

geometry ST_GeomCollFromText(text WKT);

Description

Makes a collection Geometry from the Well-Known-Text (WKT) representation with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a GEOMETRYCOLLECTION

[Note]

If you are absolutely sure all your WKT geometries are collections, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.

Examples

SELECT ST_GeomCollFromText('GEOMETRYCOLLECTION(POINT(1 2),LINESTRING(1 2, 3 4))');

Name

ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).

Synopsis

geometry ST_GeomFromEWKT(text EWKT);

Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known text (EWKT) representation.

[Note]

The EWKT format is not an OGC standard, but an PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

SELECT ST_GeomFromEWKT('SRID=4269;LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
SELECT ST_GeomFromEWKT('SRID=4269;MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

SELECT ST_GeomFromEWKT('SRID=4269;POINT(-71.064544 42.28787)');

SELECT ST_GeomFromEWKT('SRID=4269;POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

SELECT ST_GeomFromEWKT('SRID=4269;MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
-71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
-71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
-71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
-71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
-71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
-71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
-71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
-71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
-71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
-71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
-71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
-71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
-71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
-71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
-71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
-71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
-71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
-71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
-71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
-71.1031880899493 42.3152774590236)),
((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
-71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))');
--3d circular string
SELECT ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)');
--Polyhedral Surface example
SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
        ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
        ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
        ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
        ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
        ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
        ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
)');

Name

ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

Synopsis

geometry ST_GeometryFromText(text WKT);

geometry ST_GeometryFromText(text WKT, integer srid);

Description

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40


Name

ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).

Synopsis

geometry ST_GeomFromText(text WKT);

geometry ST_GeomFromText(text WKT, integer srid);

Description

Constructs a PostGIS ST_Geometry object from the OGC Well-Known text representation.

[Note]

There are two variants of ST_GeomFromText function. The first takes no SRID and returns a geometry with no defined spatial reference system (SRID=0). The second takes a SRID as the second argument and returns a geometry that includes this SRID as part of its metadata.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

This method supports Circular Strings and Curves

[Note]

While not OGC-compliant, ST_MakePoint is faster than ST_GeomFromText and ST_PointFromText. It is also easier to use for numeric coordinate values. ST_Point is another option similar in speed to ST_MakePoint and is OGC-compliant, but doesn't support anything but 2D points.

[Warning]

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written as ST_GeomFromText('GEOMETRYCOLLECTION EMPTY')

Examples

SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)',4269);

SELECT ST_GeomFromText('MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

SELECT ST_GeomFromText('POINT(-71.064544 42.28787)');

SELECT ST_GeomFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

SELECT ST_GeomFromText('MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
-71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
-71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
-71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
-71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
-71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
-71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
-71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
-71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
-71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
-71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
-71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
-71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
-71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
-71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
-71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
-71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
-71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
-71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
-71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
-71.1031880899493 42.3152774590236)),
((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
-71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))',4326);

SELECT ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)');
        

Name

ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_LineFromText(text WKT);

geometry ST_LineFromText(text WKT, integer srid);

Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0. If WKT passed in is not a LINESTRING, then null is returned.

[Note]

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

[Note]

If you know all your geometries are LINESTRINGS, its more efficient to just use ST_GeomFromText. This just calls ST_GeomFromText and adds additional validation that it returns a linestring.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.8

Examples

SELECT ST_LineFromText('LINESTRING(1 2, 3 4)') AS aline, ST_LineFromText('POINT(1 2)') AS null_return;
aline                            | null_return
------------------------------------------------
010200000002000000000000000000F ... | t
                

Name

ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.

Synopsis

geometry ST_MLineFromText(text WKT, integer srid);

geometry ST_MLineFromText(text WKT);

Description

Makes a Geometry from Well-Known-Text (WKT) with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTILINESTRING

[Note]

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.SQL-MM 3: 9.4.4

Examples

SELECT ST_MLineFromText('MULTILINESTRING((1 2, 3 4), (4 5, 6 7))');

Name

ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_MPointFromText(text WKT, integer srid);

geometry ST_MPointFromText(text WKT);

Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTIPOINT

[Note]

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. 3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.2.4

Examples

SELECT ST_MPointFromText('MULTIPOINT(1 2, 3 4)');
SELECT ST_MPointFromText('MULTIPOINT(-70.9590 42.1180, -70.9611 42.1223)', 4326);

Name

ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_MPolyFromText(text WKT, integer srid);

geometry ST_MPolyFromText(text WKT);

Description

Makes a MultiPolygon from WKT with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Throws an error if the WKT is not a MULTIPOLYGON

[Note]

If you are absolutely sure all your WKT geometries are multipolygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.6.4

Examples

SELECT ST_MPolyFromText('MULTIPOLYGON(((0 0 1,20 0 1,20 20 1,0 20 1,0 0 1),(5 5 3,5 7 3,7 7 3,7 5 3,5 5 3)))');
SELECt ST_MPolyFromText('MULTIPOLYGON(((-70.916 42.1002,-70.9468 42.0946,-70.9765 42.0872,-70.9754 42.0875,-70.9749 42.0879,-70.9752 42.0881,-70.9754 42.0891,-70.9758 42.0894,-70.9759 42.0897,-70.9759 42.0899,-70.9754 42.0902,-70.9756 42.0906,-70.9753 42.0907,-70.9753 42.0917,-70.9757 42.0924,-70.9755 42.0928,-70.9755 42.0942,-70.9751 42.0948,-70.9755 42.0953,-70.9751 42.0958,-70.9751 42.0962,-70.9759 42.0983,-70.9767 42.0987,-70.9768 42.0991,-70.9771 42.0997,-70.9771 42.1003,-70.9768 42.1005,-70.977 42.1011,-70.9766 42.1019,-70.9768 42.1026,-70.9769 42.1033,-70.9775 42.1042,-70.9773 42.1043,-70.9776 42.1043,-70.9778 42.1048,-70.9773 42.1058,-70.9774 42.1061,-70.9779 42.1065,-70.9782 42.1078,-70.9788 42.1085,-70.9798 42.1087,-70.9806 42.109,-70.9807 42.1093,-70.9806 42.1099,-70.9809 42.1109,-70.9808 42.1112,-70.9798 42.1116,-70.9792 42.1127,-70.979 42.1129,-70.9787 42.1134,-70.979 42.1139,-70.9791 42.1141,-70.9987 42.1116,-71.0022 42.1273,
        -70.9408 42.1513,-70.9315 42.1165,-70.916 42.1002)))',4326);

Name

ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.

Synopsis

geometry ST_PointFromText(text WKT);

geometry ST_PointFromText(text WKT, integer srid);

Description

Constructs a PostGIS ST_Geometry point object from the OGC Well-Known text representation. If SRID is not given, it defaults to unknown (currently 0). If geometry is not a WKT point representation, returns null. If completely invalid WKT, then throws an error.

[Note]

There are 2 variants of ST_PointFromText function, the first takes no SRID and returns a geometry with no defined spatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometry that includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

[Note]

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step. If you are building points from long lat coordinates and care more about performance and accuracy than OGC compliance, use ST_MakePoint or OGC compliant alias ST_Point.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.8

Examples

SELECT ST_PointFromText('POINT(-71.064544 42.28787)');
SELECT ST_PointFromText('POINT(-71.064544 42.28787)', 4326);
        

Name

ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

Synopsis

geometry ST_PolygonFromText(text WKT);

geometry ST_PolygonFromText(text WKT, integer srid);

Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0. Returns null if WKT is not a polygon.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

[Note]

If you are absolutely sure all your WKT geometries are polygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 8.3.6

Examples

SELECT ST_PolygonFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');
st_polygonfromtext
------------------
010300000001000000050000006...


SELECT ST_PolygonFromText('POINT(1 2)') IS NULL as point_is_notpoly;

point_is_not_poly
----------
t

Name

ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

Synopsis

geometry ST_WKTToSQL(text WKT);

Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.34

8.8.2. Well-Known Binary (WKB)

ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).
ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.
ST_LineFromWKB — Makes a LINESTRING from WKB with the given SRID
ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.
ST_PointFromWKB — Makes a geometry from WKB with the given SRID
ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid

Name

ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).

Synopsis

geography ST_GeogFromWKB(bytea wkb);

Description

The ST_GeogFromWKB function, takes a well-known binary representation (WKB) of a geometry or PostGIS Extended WKB and creates an instance of the appropriate geography type. This function plays the role of the Geometry Factory in SQL.

If SRID is not specified, it defaults to 4326 (WGS 84 long lat).

This method supports Circular Strings and Curves

Examples

--Although bytea rep contains single \, these need to be escaped when inserting into a table
SELECT ST_AsText(
ST_GeogFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@')
);
                                          st_astext
------------------------------------------------------
 LINESTRING(-113.98 39.198,-113.981 39.195)
(1 row)


Name

ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).

Synopsis

geometry ST_GeomFromEWKB(bytea EWKB);

Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known binary (EWKT) representation.

[Note]

The EWKB format is not an OGC standard, but a PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

line string binary rep 0f LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932) in NAD 83 long lat (4269).

[Note]

NOTE: Even though byte arrays are delimited with \ and may have ', we need to escape both out with \ and '' if standard_conforming_strings is off. So it does not look exactly like its AsEWKB representation.

SELECT ST_GeomFromEWKB(E'\\001\\002\\000\\000 \\255\\020\\000\\000\\003\\000\\000\\000\\344J=
\\013B\\312Q\\300n\\303(\\010\\036!E@''\\277E''K
\\312Q\\300\\366{b\\235*!E@\\225|\\354.P\\312Q
\\300p\\231\\323e1!E@');
[Note]

In PostgreSQL 9.1+ - standard_conforming_strings is set to on by default, where as in past versions it was set to off. You can change defaults as needed for a single query or at the database or server level. Below is how you would do it with standard_conforming_strings = on. In this case we escape the ' with standard ansi ', but slashes are not escaped

set standard_conforming_strings = on;
SELECT ST_GeomFromEWKB('\001\002\000\000 \255\020\000\000\003\000\000\000\344J=\012\013B
    \312Q\300n\303(\010\036!E@''\277E''K\012\312Q\300\366{b\235*!E@\225|\354.P\312Q\012\300p\231\323e1')

Name

ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.

Synopsis

geometry ST_GeomFromWKB(bytea geom);

geometry ST_GeomFromWKB(bytea geom, integer srid);

Description

The ST_GeomFromWKB function, takes a well-known binary representation of a geometry and a Spatial Reference System ID (SRID) and creates an instance of the appropriate geometry type. This function plays the role of the Geometry Factory in SQL. This is an alternate name for ST_WKBToSQL.

If SRID is not specified, it defaults to 0 (Unknown).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.7.2 - the optional SRID is from the conformance suite

This method implements the SQL/MM specification. SQL-MM 3: 5.1.41

This method supports Circular Strings and Curves

Examples

--Although bytea rep contains single \, these need to be escaped when inserting into a table
                -- unless standard_conforming_strings is set to on.
SELECT ST_AsEWKT(
ST_GeomFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@',4326)
);
                                          st_asewkt
------------------------------------------------------
 SRID=4326;LINESTRING(-113.98 39.198,-113.981 39.195)
(1 row)

SELECT
  ST_AsText(
        ST_GeomFromWKB(
          ST_AsEWKB('POINT(2 5)'::geometry)
        )
  );
 st_astext
------------
 POINT(2 5)
(1 row)

Name

ST_LineFromWKB — Makes a LINESTRING from WKB with the given SRID

Synopsis

geometry ST_LineFromWKB(bytea WKB);

geometry ST_LineFromWKB(bytea WKB, integer srid);

Description

The ST_LineFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID (SRID) and creates an instance of the appropriate geometry type - in this case, a LINESTRING geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. NULL is returned if the input bytea does not represent a LINESTRING.

[Note]

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

[Note]

If you know all your geometries are LINESTRINGs, its more efficient to just use ST_GeomFromWKB. This function just calls ST_GeomFromWKB and adds additional validation that it returns a linestring.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

Examples

SELECT ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))) AS aline,
                ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('POINT(1 2)'))) IS NULL AS null_return;
aline                            | null_return
------------------------------------------------
010200000002000000000000000000F ... | t
                

Name

ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.

Synopsis

geometry ST_LinestringFromWKB(bytea WKB);

geometry ST_LinestringFromWKB(bytea WKB, integer srid);

Description

The ST_LinestringFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID (SRID) and creates an instance of the appropriate geometry type - in this case, a LINESTRING geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. NULL is returned if the input bytea does not represent a LINESTRING geometry. This an alias for ST_LineFromWKB.

[Note]

OGC SPEC 3.2.6.2 - optional SRID is from the conformance suite.

[Note]

If you know all your geometries are LINESTRINGs, it's more efficient to just use ST_GeomFromWKB. This function just calls ST_GeomFromWKB and adds additional validation that it returns a LINESTRING.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

Examples

SELECT
  ST_LineStringFromWKB(
        ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))
  ) AS aline,
  ST_LinestringFromWKB(
        ST_AsBinary(ST_GeomFromText('POINT(1 2)'))
  ) IS NULL AS null_return;
   aline                            | null_return
------------------------------------------------
010200000002000000000000000000F ... | t

Name

ST_PointFromWKB — Makes a geometry from WKB with the given SRID

Synopsis

geometry ST_GeomFromWKB(bytea geom);

geometry ST_GeomFromWKB(bytea geom, integer srid);

Description

The ST_PointFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID (SRID) and creates an instance of the appropriate geometry type - in this case, a POINT geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. NULL is returned if the input bytea does not represent a POINT geometry.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.7.2

This method implements the SQL/MM specification. SQL-MM 3: 6.1.9

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT
  ST_AsText(
        ST_PointFromWKB(
          ST_AsEWKB('POINT(2 5)'::geometry)
        )
  );
 st_astext
------------
 POINT(2 5)
(1 row)

SELECT
  ST_AsText(
        ST_PointFromWKB(
          ST_AsEWKB('LINESTRING(2 5, 2 6)'::geometry)
        )
  );
 st_astext
-----------

(1 row)

Name

ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid

Synopsis

geometry ST_WKBToSQL(bytea WKB);

Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.36

8.8.3. Other Formats

ST_Box2dFromGeoHash — Return a BOX2D from a GeoHash string.
ST_GeomFromGeoHash — Return a geometry from a GeoHash string.
ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object
ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object
ST_GeomFromTWKB — Creates a geometry instance from a TWKB ("Tiny Well-Known Binary") geometry representation.
ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
ST_LineFromEncodedPolyline — Creates a LineString from an Encoded Polyline.
ST_PointFromGeoHash — Return a point from a GeoHash string.

Name

ST_Box2dFromGeoHash — Return a BOX2D from a GeoHash string.

Synopsis

box2d ST_Box2dFromGeoHash(text geohash, integer precision=full_precision_of_geohash);

Description

Return a BOX2D from a GeoHash string.

If no precision is specficified ST_Box2dFromGeoHash returns a BOX2D based on full precision of the input GeoHash string.

If precision is specified ST_Box2dFromGeoHash will use that many characters from the GeoHash to create the BOX2D. Lower precision values results in larger BOX2Ds and larger values increase the precision.

Availability: 2.1.0

Examples

SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0');

                st_geomfromgeohash
--------------------------------------------------
 BOX(-115.172816 36.114646,-115.172816 36.114646)

SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 0);

 st_box2dfromgeohash
----------------------
 BOX(-180 -90,180 90)

 SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10);
                            st_box2dfromgeohash
---------------------------------------------------------------------------
 BOX(-115.17282128334 36.1146408319473,-115.172810554504 36.1146461963654)
                
                

Name

ST_GeomFromGeoHash — Return a geometry from a GeoHash string.

Synopsis

geometry ST_GeomFromGeoHash(text geohash, integer precision=full_precision_of_geohash);

Description

Return a geometry from a GeoHash string. The geometry will be a polygon representing the GeoHash bounds.

If no precision is specified ST_GeomFromGeoHash returns a polygon based on full precision of the input GeoHash string.

If precision is specified ST_GeomFromGeoHash will use that many characters from the GeoHash to create the polygon.

Availability: 2.1.0

Examples

SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0'));
                                                        st_astext
--------------------------------------------------------------------------------------------------------------------------
 POLYGON((-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646))

SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 4));
                                                          st_astext
------------------------------------------------------------------------------------------------------------------------------
 POLYGON((-115.3125 36.03515625,-115.3125 36.2109375,-114.9609375 36.2109375,-114.9609375 36.03515625,-115.3125 36.03515625))

SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10));
                                                                                       st_astext
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 POLYGON((-115.17282128334 36.1146408319473,-115.17282128334 36.1146461963654,-115.172810554504 36.1146461963654,-115.172810554504 36.1146408319473,-115.17282128334 36.1146408319473))
                
                

Name

ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromGML(text geomgml);

geometry ST_GeomFromGML(text geomgml, integer srid);

Description

Constructs a PostGIS ST_Geometry object from the OGC GML representation.

ST_GeomFromGML works only for GML Geometry fragments. It throws an error if you try to use it on a whole GML document.

OGC GML versions supported:

  • GML 3.2.1 Namespace

  • GML 3.1.1 Simple Features profile SF-2 (with GML 3.1.0 and 3.0.0 backward compatibility)

  • GML 2.1.2

OGC GML standards, cf: http://www.opengeospatial.org/standards/gml:

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

GML allow mixed dimensions (2D and 3D inside the same MultiGeometry for instance). As PostGIS geometries don't, ST_GeomFromGML convert the whole geometry to 2D if a missing Z dimension is found once.

GML support mixed SRS inside the same MultiGeometry. As PostGIS geometries don't, ST_GeomFromGML, in this case, reproject all subgeometries to the SRS root node. If no srsName attribute available for the GML root node, the function throw an error.

ST_GeomFromGML function is not pedantic about an explicit GML namespace. You could avoid to mention it explicitly for common usages. But you need it if you want to use XLink feature inside GML.

[Note]

ST_GeomFromGML function not support SQL/MM curves geometries.

Examples - A single geometry with srsName

SELECT ST_GeomFromGML('
                <gml:LineString srsName="EPSG:4269">
                        <gml:coordinates>
                                -71.16028,42.258729 -71.160837,42.259112 -71.161143,42.25932
                        </gml:coordinates>
                </gml:LineString>');
                

Examples - XLink usage

SELECT ST_GeomFromGML('
                <gml:LineString xmlns:gml="http://www.opengis.net/gml"
                                xmlns:xlink="http://www.w3.org/1999/xlink"
                                srsName="urn:ogc:def:crs:EPSG::4269">
                        <gml:pointProperty>
                                <gml:Point gml:id="p1"><gml:pos>42.258729 -71.16028</gml:pos></gml:Point>
                        </gml:pointProperty>
                        <gml:pos>42.259112 -71.160837</gml:pos>
                        <gml:pointProperty>
                                <gml:Point xlink:type="simple" xlink:href="#p1"/>
                        </gml:pointProperty>
                </gml:LineString>'););
                

Examples - Polyhedral Surface

SELECT ST_AsEWKT(ST_GeomFromGML('
<gml:PolyhedralSurface>
<gml:polygonPatches>
  <gml:PolygonPatch>
    <gml:exterior>
      <gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
        <gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
        <gml:LinearRing><gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
        <gml:LinearRing><gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
        <gml:LinearRing><gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
  <gml:PolygonPatch>
    <gml:exterior>
        <gml:LinearRing><gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList></gml:LinearRing>
    </gml:exterior>
  </gml:PolygonPatch>
</gml:polygonPatches>
</gml:PolyhedralSurface>'));

-- result --
 POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
 ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
 ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
 ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
 ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
 ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))
                

Name

ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromGeoJSON(text geomjson);

geometry ST_GeomFromGeoJSON(json geomjson);

geometry ST_GeomFromGeoJSON(jsonb geomjson);

Description

Constructs a PostGIS geometry object from the GeoJSON representation.

ST_GeomFromGeoJSON works only for JSON Geometry fragments. It throws an error if you try to use it on a whole JSON document.

Enhanced: 3.0.0 parsed geometry defaults to SRID=4326 if not specified otherwise.

Enhanced: 2.5.0 can now accept json and jsonb as inputs.

Availability: 2.0.0 requires - JSON-C >= 0.9

[Note]

If you do not have JSON-C enabled, support you will get an error notice instead of seeing an output. To enable JSON-C, run configure --with-jsondir=/path/to/json-c. See Section 2.2.3, “Configurazione” for details.

This function supports 3d and will not drop the z-index.

Examples

SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"Point","coordinates":[-48.23456,20.12345]}')) As wkt;
wkt
------
POINT(-48.23456 20.12345)
-- a 3D linestring
SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"LineString","coordinates":[[1,2,3],[4,5,6],[7,8,9]]}')) As wkt;

wkt
-------------------
LINESTRING(1 2,4 5,7 8)

Name

ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromKML(text geomkml);

Description

Constructs a PostGIS ST_Geometry object from the OGC KML representation.

ST_GeomFromKML works only for KML Geometry fragments. It throws an error if you try to use it on a whole KML document.

OGC KML versions supported:

  • KML 2.2.0 Namespace

OGC KML standards, cf: http://www.opengeospatial.org/standards/kml:

Availability: 1.5, requires libxml2 2.6+

This function supports 3d and will not drop the z-index.

[Note]

ST_GeomFromKML function not support SQL/MM curves geometries.

Examples - A single geometry with srsName

SELECT ST_GeomFromKML('
                <LineString>
                        <coordinates>-71.1663,42.2614
                                -71.1667,42.2616</coordinates>
                </LineString>');
                

Name

ST_GeomFromTWKB — Creates a geometry instance from a TWKB ("Tiny Well-Known Binary") geometry representation.

Synopsis

geometry ST_GeomFromTWKB(bytea twkb);

Description

The ST_GeomFromTWKB function, takes a a TWKB ("Tiny Well-Known Binary") geometry representation (WKB) and creates an instance of the appropriate geometry type.

Examples

SELECT ST_AsText(ST_GeomFromTWKB(ST_AsTWKB('LINESTRING(126 34, 127 35)'::geometry)));

         st_astext
-----------------------------
 LINESTRING(126 34, 127 35)
(1 row)


SELECT ST_AsEWKT(
  ST_GeomFromTWKB(E'\\x620002f7f40dbce4040105')
);
                                          st_asewkt
------------------------------------------------------
LINESTRING(-113.98 39.198,-113.981 39.195)
(1 row)

See Also

ST_AsTWKB


Name

ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML

Synopsis

geometry ST_GMLToSQL(text geomgml);

geometry ST_GMLToSQL(text geomgml, integer srid);

Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.50 (except for curves support).

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.


Name

ST_LineFromEncodedPolyline — Creates a LineString from an Encoded Polyline.

Synopsis

geometry ST_LineFromEncodedPolyline(text polyline, integer precision=5);

Description

Creates a LineString from an Encoded Polyline string.

Optional precision specifies how many decimal places will be preserved in Encoded Polyline. Value should be the same on encoding and decoding, or coordinates will be incorrect.

See http://developers.google.com/maps/documentation/utilities/polylinealgorithm

Availability: 2.2.0

Examples

-- Create a line string from a polyline
SELECT ST_AsEWKT(ST_LineFromEncodedPolyline('_p~iF~ps|U_ulLnnqC_mqNvxq`@'));
-- result --
SRID=4326;LINESTRING(-120.2 38.5,-120.95 40.7,-126.453 43.252)

-- Select different precision that was used for polyline encoding
SELECT ST_AsEWKT(ST_LineFromEncodedPolyline('_p~iF~ps|U_ulLnnqC_mqNvxq`@',6));
-- result --
SRID=4326;LINESTRING(-12.02 3.85,-12.095 4.07,-12.6453 4.3252)

    

Name

ST_PointFromGeoHash — Return a point from a GeoHash string.

Synopsis

point ST_PointFromGeoHash(text geohash, integer precision=full_precision_of_geohash);

Description

Return a point from a GeoHash string. The point represents the center point of the GeoHash.

If no precision is specified ST_PointFromGeoHash returns a point based on full precision of the input GeoHash string.

If precision is specified ST_PointFromGeoHash will use that many characters from the GeoHash to create the point.

Availability: 2.1.0

Examples

SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0'));
          st_astext
------------------------------
 POINT(-115.172816 36.114646)

SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 4));
             st_astext
-----------------------------------
 POINT(-115.13671875 36.123046875)

SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10));
                 st_astext
-------------------------------------------
 POINT(-115.172815918922 36.1146435141563)
                
                

8.9. Geometry Output

Abstract

These functions convert geometry objects into various textual or binary formats.

8.9.1. Well-Known Text (WKT)

ST_AsEWKT — Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

Name

ST_AsEWKT — Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.

Synopsis

bytea ST_AsBinary(geometry g1);

bytea ST_AsBinary(geometry g1, text NDR_or_XDR);

bytea ST_AsBinary(geography g1);

bytea ST_AsBinary(geography g1, text NDR_or_XDR);

Descrizione

Returns the Well-Known Text representation of the geometry prefixed with the SRID. Optional argument may be used to reduce the maximum number of decimal digits after floating point used in output (defaults to 15).

[Note]

The WKT spec does not include the SRID. To get the OGC WKT format use ST_AsText.

[Warning]

WKT format does not maintain precision so to prevent floating truncation, use ST_AsBinary or ST_AsEWKB format for transport.

[Note]

ST_AsEWKT is the reverse of ST_GeomFromEWKT. Use ST_GeomFromEWKT to convert to a postgis geometry from ST_AsEWKT representation.

Enhanced: 3.1.0 support for optional precision parameter.

Enhanced: 2.0.0 support for Geography, Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

SELECT ST_AsEWKT('0103000020E61000000100000005000000000000
                        000000000000000000000000000000000000000000000000000000
                        F03F000000000000F03F000000000000F03F000000000000F03
                        F000000000000000000000000000000000000000000000000'::geometry);

                   st_asewkt
--------------------------------
SRID=4326;POLYGON((0 0,0 1,1 1,1 0,0 0))
(1 row)

SELECT ST_AsEWKT('0108000080030000000000000060E30A4100000000785C0241000000000000F03F0000000018
E20A4100000000485F024100000000000000400000000018
E20A4100000000305C02410000000000000840')

--st_asewkt---
CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)

Name

ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

Synopsis

bytea ST_AsBinary(geometry g1);

bytea ST_AsBinary(geometry g1, text NDR_or_XDR);

bytea ST_AsBinary(geography g1);

bytea ST_AsBinary(geography g1, text NDR_or_XDR);

Descrizione

Returns the OGC Well-Known Text (WKT) representation of the geometry/geography. The optional maxdecimaldigits argument may be used to limit the number of digits after the decimal point in output ordinates (defaults to 15).

To perform the inverse conversion of WKT representation to PostGIS geometry use ST_GeomFromText.

[Note]

The standard OGC WKT representation does not include the SRID. To include the SRID as part of the output representation, use the non-standard PostGIS function ST_AsEWKT

[Warning]

The textual representation of numbers in WKT may not maintain full floating-point precision. To ensure full accuracy for data storage or transport it is best to use Well-Known Binary (WKB) format (see ST_AsBinary and ST_AsEWKB).

Availability: 1.5 - support for geography was introduced.

Enhanced: 2.5 - optional parameter precision introduced.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

This method supports Circular Strings and Curves

Esempi

SELECT ST_AsText('01030000000100000005000000000000000000
000000000000000000000000000000000000000000000000
F03F000000000000F03F000000000000F03F000000000000F03
F000000000000000000000000000000000000000000000000');

                   st_astext
--------------------------------
 POLYGON((0 0,0 1,1 1,1 0,0 0))
(1 row)

Full precision output is the default.

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)'));
      st_aslatlontext       
----------------------------
 2°19'29.928"S 3°14'3.243"W

The maxdecimaldigits argument can be used to limit output precision.

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)'));
      st_aslatlontext       
----------------------------
 2°19'29.928"S 3°14'3.243"W

8.9.2. Well-Known Binary (WKB)

ST_AsBinary — Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
ST_AsEWKB — Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.
ST_AsHEXEWKB — Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.

Name

ST_AsBinary — Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.

Synopsis

bytea ST_AsBinary(geometry g1);

bytea ST_AsBinary(geometry g1, text NDR_or_XDR);

bytea ST_AsBinary(geography g1);

bytea ST_AsBinary(geography g1, text NDR_or_XDR);

Descrizione

Returns the OGC/ISO Well-Known Binary (WKB) representation of the geometry. The first function variant defaults to encoding using server machine endian. The second function variant takes a text argument specifying the endian encoding, either little-endian ('NDR') or big-endian ('XDR').

WKB format is useful to read geometry data from the database and maintaining full numeric precision. This avoids the precision rounding that can happen with text formats such as WKT.

To perform the inverse conversion of WKB to PostGIS geometry use ST_GeomFromWKB.

[Note]

The OGC/ISO WKB format does not include the SRID. To get the EWKB format which does include the SRID use ST_AsEWKB

[Note]

The default behavior in PostgreSQL 9.0 has been changed to output bytea in hex encoding. If your GUI tools require the old behavior, then SET bytea_output='escape' in your database.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 support for higher coordinate dimensions was introduced.

Enhanced: 2.0.0 support for specifying endian with geography was introduced.

Availability: 1.5.0 geography support was introduced.

Changed: 2.0.0 Inputs to this function can not be unknown -- must be geometry. Constructs such as ST_AsBinary('POINT(1 2)') are no longer valid and you will get an n st_asbinary(unknown) is not unique error. Code like that needs to be changed to ST_AsBinary('POINT(1 2)'::geometry);. If that is not possible, then install legacy.sql.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.37

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

                   st_asbinary
--------------------------------
\001\003\000\000\000\001\000\000\000\005
\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000
\000\000\000\360?\000\000\000\000\000\000
\360?\000\000\000\000\000\000\360?\000\000
\000\000\000\000\360?\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000
(1 row)
SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
                   st_asbinary
--------------------------------
\000\000\000\000\003\000\000\000\001\000\000\000\005\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000
\000\000\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
(1 row)

Name

ST_AsEWKB — Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.

Synopsis

bytea ST_AsEWKB(geometry g1);

bytea ST_AsEWKB(geometry g1, text NDR_or_XDR);

Descrizione

Returns the Extended Well-Known Binary (EWKB) representation of the geometry with SRID metadata. The first function variant defaults to encoding using server machine endian. The second function variant takes a text argument specifying the endian encoding, either little-endian ('NDR') or big-endian ('XDR').

WKB format is useful to read geometry data from the database and maintaining full numeric precision. This avoids the precision rounding that can happen with text formats such as WKT.

To perform the inverse conversion of EWKB to PostGIS geometry use ST_GeomFromEWKB.

[Note]

To get the OGC/ISO WKB format use ST_AsBinary. Note that OGC/ISO WKB format does not include the SRID.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Esempi

SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
                   st_asewkb
--------------------------------
\000 \000\000\003\000\000\020\346\000\000\000\001\000\000\000\005\000\000\000\000\
000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000?
\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000
\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000\000\000
SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
                   st_asewkb
--------------------------------
\000 \000\000\003\000\000\020\346\000\000\000\001\000\000\000\005\000\000\000\000\
000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000?
\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000
\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
\000\000\000\000\000\000\000\000\000\000\000\000\000
                

Name

ST_AsHEXEWKB — Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.

Synopsis

text ST_AsHEXEWKB(geometry g1, text NDRorXDR);

text ST_AsHEXEWKB(geometry g1);

Descrizione

Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding. If no encoding is specified, then NDR is used.

[Note]

Availability: 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Esempi

SELECT ST_AsHEXEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));
                dà la stessa risposta di

                SELECT ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326)::text;

                st_ashexewkb
                --------
                0103000020E6100000010000000500
                00000000000000000000000000000000
                00000000000000000000000000000000F03F
                000000000000F03F000000000000F03F000000000000F03
                F000000000000000000000000000000000000000000000000

8.9.3. Other Formats

ST_AsEncodedPolyline — Returns an Encoded Polyline from a LineString geometry.
ST_AsGeoJSON — Return a Geobuf representation of a set of rows.
ST_AsGeoJSON — Restisuisce la geometria come elemento GeoJSON.
ST_AsGML — Return the geometry as a GML version 2 or 3 element.
ST_AsKML — Return the geometry as a KML element. Several variants. Default version=2, default maxdecimaldigits=15
ST_AsLatLonText — Return the Degrees, Minutes, Seconds representation of the given point.
ST_AsSVG — Transform a geometry into the coordinate space of a Mapbox Vector Tile.
ST_AsGML — Aggregate function returning a Mapbox Vector Tile representation of a set of rows.
ST_AsSVG — Returns SVG path data for a geometry.
ST_AsTWKB — Returns the geometry as TWKB, aka "Tiny Well-Known Binary"
ST_AsX3D — Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
ST_GeoHash — Return a GeoHash representation of the geometry.

Name

ST_AsEncodedPolyline — Returns an Encoded Polyline from a LineString geometry.

Synopsis

text ST_AsEncodedPolyline(geometry geom, integer precision=5);

Descrizione

Returns the geometry as an Encoded Polyline. This format is used by Google Maps with precision=5 and by Open Source Routing Machine with precision=5 and 6.

Optional precision specifies how many decimal places will be preserved in Encoded Polyline. Value should be the same on encoding and decoding, or coordinates will be incorrect.

Availability: 2.2.0

Esempi

Basic

SELECT ST_AsEncodedPolyline(GeomFromEWKT('SRID=4326;LINESTRING(-120.2 38.5,-120.95 40.7,-126.453 43.252)'));
        --result--
        |_p~iF~ps|U_ulLnnqC_mqNvxq`@
        

Use in conjunction with geography linestring and geography segmentize, and put on google maps

-- the SQL for Boston to San Francisco, segments every 100 KM
        SELECT ST_AsEncodedPolyline(
                ST_Segmentize(
                        ST_GeogFromText('LINESTRING(-71.0519 42.4935,-122.4483 37.64)'),
                                100000)::geometry) As encodedFlightPath;

javascript will look something like this where $ variable you replace with query result

<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?libraries=geometry"></script>
<script type="text/javascript">
         flightPath = new google.maps.Polyline({
                        path:  google.maps.geometry.encoding.decodePath("$encodedFlightPath"),
                        map: map,
                        strokeColor: '#0000CC',
                        strokeOpacity: 1.0,
                        strokeWeight: 4
                });
</script>
        

Name

ST_AsGeoJSON — Return a Geobuf representation of a set of rows.

Synopsis

bytea ST_AsEWKB(geometry g1);

bytea ST_AsEWKB(geometry g1, text NDR_or_XDR);

Descrizione

Return a Geobuf representation (https://github.com/mapbox/geobuf) of a set of rows corresponding to a FeatureCollection. Every input geometry is analyzed to determine maximum precision for optimal storage. Note that Geobuf in its current form cannot be streamed so the full output will be assembled in memory.

row row data with at least a geometry column.

geom_name is the name of the geometry column in the row data. If NULL it will default to the first found geometry column.

Disponibilità: 1.4.0

Esempi

SELECT encode(ST_AsGeobuf(q, 'geom'), 'base64')
    FROM (SELECT ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))') AS geom) AS q;
 st_asgeobuf
----------------------------------
 GAAiEAoOCgwIBBoIAAAAAgIAAAE=

                
                

Name

ST_AsGeoJSON — Restisuisce la geometria come elemento GeoJSON.

Synopsis

text ST_AsGeoJSON(geometry geom, integer maxdecimaldigits=15, integer options=0);

text ST_AsGeoJSON(geography geog, integer maxdecimaldigits=15, integer options=0);

text ST_AsGeoJSON(integer gj_version, geometry geom, integer maxdecimaldigits=15, integer options=0);

text ST_AsGeoJSON(integer gj_version, geography geog, integer maxdecimaldigits=15, integer options=0);

Descrizione

Returns a geometry as a GeoJSON "geometry", or a row as a GeoJSON "feature". (See the GeoJSON specifications RFC 7946). 2D and 3D Geometries are both supported. GeoJSON only support SFS 1.1 geometry types (no curve support for example).

The maxdecimaldigits argument may be used to reduce the maximum number of decimal places used in output (defaults to 9). If you are using EPSG:4326 and are outputting the geometry only for display, maxdecimaldigits=6 can be a good choice for many maps.

The options argument can be used to add BBOX or CRS in GeoJSON output:

  • 0: means no option

  • 1: GeoJSON BBOX

  • 2: GeoJSON Short CRS (e.g EPSG:4326)

  • 4: GeoJSON Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

  • 8: GeoJSON Short CRS if not EPSG:4326 (default)

The GeoJSON specification states that polygons are oriented using the Right-Hand Rule, and some clients require this orientation. This can be ensured by using ST_ForcePolygonCCW . The specification also requires that geometry be in the WGS84 coordinate system (SRID = 4326). If necessary geometry can be projected into WGS84 using ST_Transform: ST_Transform( geom, 4326 ).

GeoJSON can be tested and viewed online at geojson.io and geojsonlint.com. It is widely supported by web mapping frameworks:

Disponibilità: 1.3.4

Availability: 1.5.0 geography support was introduced.

Changed: 2.0.0 support default args and named args.

Changed: 3.0.0 support records as input

Changed: 3.0.0 output SRID if not EPSG:4326.

This function supports 3d and will not drop the z-index.

Esempi

Generate a FeatureCollection:

SELECT json_build_object(
    'type', 'FeatureCollection',
    'features', json_agg(ST_AsGeoJSON(t.*)::json)
    )
FROM ( VALUES (1, 'one', 'POINT(1 1)'::geometry),
              (2, 'two', 'POINT(2 2)'),
              (3, 'three', 'POINT(3 3)')
     ) as t(id, name, geom);
{"type" : "FeatureCollection", "features" : [{"type": "Feature", "geometry": {"type":"Point","coordinates":[1,1]}, "properties": {"id": 1, "name": "one"}}, {"type": "Feature", "geometry": {"type":"Point","coordinates":[2,2]}, "properties": {"id": 2, "name": "two"}}, {"type": "Feature", "geometry": {"type":"Point","coordinates":[3,3]}, "properties": {"id": 3, "name": "three"}}]}

Generate a Feature:

SELECT ST_AsGeoJSON(t.*)
FROM (VALUES (1, 'one', 'POINT(1 1)'::geometry)) AS t(id, name, geom);
SELECT ST_AsGeoJSON(the_geom) from fe_edges limit 1;
                                           st_asgeojson
-----------------------------------------------------------------------------------------------------------

{"type":"MultiLineString","coordinates":[[[-89.734634999999997,31.492072000000000],
[-89.734955999999997,31.492237999999997]]]}
(1 row)
--3d point
SELECT ST_AsGeoJSON('LINESTRING(1 2 3, 4 5 6)');

st_asgeojson
-----------------------------------------------------------------------------------------
 {"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

An alternate way to generate Features with an id property is to use JSONB functions and operators:

SELECT jsonb_build_object(
    'type',       'Feature',
    'id',         id,
    'geometry',   ST_AsGeoJSON(geom)::jsonb,
    'properties', to_jsonb( t.* ) - 'id' - 'geom'
    ) AS json
FROM (VALUES (1, 'one', 'POINT(1 1)'::geometry)) AS t(id, name, geom);
SELECT ST_AsGeoJSON(the_geom) from fe_edges limit 1;
                                           st_asgeojson
-----------------------------------------------------------------------------------------------------------

{"type":"MultiLineString","coordinates":[[[-89.734634999999997,31.492072000000000],
[-89.734955999999997,31.492237999999997]]]}
(1 row)
--3d point
SELECT ST_AsGeoJSON('LINESTRING(1 2 3, 4 5 6)');

st_asgeojson
-----------------------------------------------------------------------------------------
 {"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

Don't forget to transform your data to WGS84 longitude, latitude to conform with the GeoJSON specification:

SELECT ST_AsGeoJSON(ST_Transform(geom,4326)) from fe_edges limit 1;
SELECT ST_AsGeoJSON(the_geom) from fe_edges limit 1;
                                           st_asgeojson
-----------------------------------------------------------------------------------------------------------

{"type":"MultiLineString","coordinates":[[[-89.734634999999997,31.492072000000000],
[-89.734955999999997,31.492237999999997]]]}
(1 row)
--3d point
SELECT ST_AsGeoJSON('LINESTRING(1 2 3, 4 5 6)');

st_asgeojson
-----------------------------------------------------------------------------------------
 {"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

3D geometries are supported:

SELECT ST_AsGeoJSON('LINESTRING(1 2 3, 4 5 6)');
{"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

Name

ST_AsGML — Return the geometry as a GML version 2 or 3 element.

Synopsis

text ST_AsGeoJSON(geometry geom, integer maxdecimaldigits=15, integer options=0);

text ST_AsGeoJSON(geography geog, integer maxdecimaldigits=15, integer options=0);

text ST_AsGeoJSON(integer gj_version, geometry geom, integer maxdecimaldigits=15, integer options=0);

text ST_AsGeoJSON(integer gj_version, geography geog, integer maxdecimaldigits=15, integer options=0);

Descrizione

Return the geometry as a Geography Markup Language (GML) element. The version parameter, if specified, may be either 2 or 3. If no version parameter is specified then the default is assumed to be 2. The maxdecimaldigits argument may be used to reduce the maximum number of decimal places used in output (defaults to 15).

GML 2 refer to 2.1.2 version, GML 3 to 3.1.1 version

The 'options' argument is a bitfield. It could be used to define CRS output type in GML output, and to declare data as lat/lon:

  • 0: GML Short CRS (e.g EPSG:4326), default value

  • 1: GML Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

  • 2: For GML 3 only, remove srsDimension attribute from output.

  • 4: For GML 3 only, use <LineString> rather than <Curve> tag for lines.

  • 16: Declare that datas are lat/lon (e.g srid=4326). Default is to assume that data are planars. This option is useful for GML 3.1.1 output only, related to axis order. So if you set it, it will swap the coordinates so order is lat lon instead of database lon lat.

  • 32: Output the box of the geometry (envelope).

The 'namespace prefix' argument may be used to specify a custom namespace prefix or no prefix (if empty). If null or omitted 'gml' prefix is used

Disponibilità: 1.3.2

Availability: 1.5.0 geography support was introduced.

Enhanced: 2.0.0 prefix support was introduced. Option 4 for GML3 was introduced to allow using LineString instead of Curve tag for lines. GML3 Support for Polyhedral surfaces and TINS was introduced. Option 32 was introduced to output the box.

Changed: 2.0.0 use default named args

Enhanced: 2.1.0 id support was introduced, for GML 3.

[Note]

Only version 3+ of ST_AsGML supports Polyhedral Surfaces and TINS.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples: Version 2

SELECT ST_AsGML(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));
                st_asgml
                --------
                <gml:Polygon srsName="EPSG:4326"
><gml:outerBoundaryIs
><gml:LinearRing
><gml:coordinates
>0,0 0,1 1,1 1,0 0,0</gml:coordinates
></gml:LinearRing
></gml:outerBoundaryIs
></gml:Polygon
>
                        

Esempi: Versione 3

-- Flip coordinates and output extended EPSG (16 | 1)--
SELECT ST_AsGML(3, ST_GeomFromText('POINT(5.234234233242 6.34534534534)',4326), 5, 17);
                        st_asgml
                        --------
                <gml:Point srsName="urn:ogc:def:crs:EPSG::4326"><gml:pos>6.34535 5.23423</gml:pos></gml:Point>
                        
-- Output the envelope (32) --
SELECT ST_AsGML(3, ST_GeomFromText('LINESTRING(1 2, 3 4, 10 20)',4326), 5, 32);
                st_asgml
                --------
        <gml:Envelope srsName="EPSG:4326">
                <gml:lowerCorner>1 2</gml:lowerCorner>
                <gml:upperCorner>10 20</gml:upperCorner>
        </gml:Envelope>
                        
-- Output the envelope (32) , reverse (lat lon instead of lon lat) (16), long srs (1)= 32 | 16 | 1 = 49 --
SELECT ST_AsGML(3, ST_GeomFromText('LINESTRING(1 2, 3 4, 10 20)',4326), 5, 49);
        st_asgml
        --------
<gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
        <gml:lowerCorner>2 1</gml:lowerCorner>
        <gml:upperCorner>20 10</gml:upperCorner>
</gml:Envelope>
                        
-- Polyhedral Example --
SELECT ST_AsGML(3, ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
        st_asgml
        --------
 <gml:PolyhedralSurface>
<gml:polygonPatches>
   <gml:PolygonPatch>
                <gml:exterior>
                          <gml:LinearRing>
                                   <gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList>
                          </gml:LinearRing>
                </gml:exterior>
   </gml:PolygonPatch>
   <gml:PolygonPatch>
                <gml:exterior>
                          <gml:LinearRing>
                                   <gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList>
                          </gml:LinearRing>
                </gml:exterior>
   </gml:PolygonPatch>
   <gml:PolygonPatch>
                <gml:exterior>
                          <gml:LinearRing>
                                   <gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList>
                          </gml:LinearRing>
                </gml:exterior>
   </gml:PolygonPatch>
   <gml:PolygonPatch>
                <gml:exterior>
                          <gml:LinearRing>
                                   <gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList>
                          </gml:LinearRing>
                </gml:exterior>
   </gml:PolygonPatch>
   <gml:PolygonPatch>
                <gml:exterior>
                          <gml:LinearRing>
                                   <gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList>
                          </gml:LinearRing>
                </gml:exterior>
   </gml:PolygonPatch>
   <gml:PolygonPatch>
                <gml:exterior>
                          <gml:LinearRing>
                                   <gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList>
                          </gml:LinearRing>
                </gml:exterior>
   </gml:PolygonPatch>
</gml:polygonPatches>
</gml:PolyhedralSurface>
                        

Si veda anche

ST_GeomFromGML


Name

ST_AsKML — Return the geometry as a KML element. Several variants. Default version=2, default maxdecimaldigits=15

Synopsis

text ST_AsSVG(geometry geom, integer rel=0, integer maxdecimaldigits=15);

text ST_AsSVG(geography geog, integer rel=0, integer maxdecimaldigits=15);

Descrizione

Return the geometry as a Keyhole Markup Language (KML) element. There are several variants of this function. maximum number of decimal places used in output (defaults to 15), version default to 2 and default namespace is no prefix.

Version 1: ST_AsKML(geom_or_geog, maxdecimaldigits) / version=2 / maxdecimaldigits=15

Version 2: ST_AsKML(version, geom_or_geog, maxdecimaldigits, nprefix) maxdecimaldigits=15 / nprefix=NULL

[Note]

Requires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiled in.

[Note]

Availability: 1.2.2 - later variants that include version param came in 1.3.2

[Note]

Enhanced: 2.0.0 - Add prefix namespace. Default is no prefix

[Note]

Changed: 2.0.0 - uses default args and supports named args

[Note]

AsKML output will not work with geometries that do not have an SRID

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_AsKML(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

                st_askml
                --------
                <Polygon
><outerBoundaryIs
><LinearRing
><coordinates
>0,0 0,1 1,1 1,0 0,0</coordinates
></LinearRing
></outerBoundaryIs
></Polygon>

                --3d linestring
                SELECT ST_AsKML('SRID=4326;LINESTRING(1 2 3, 4 5 6)');
                <LineString
><coordinates
>1,2,3 4,5,6</coordinates
></LineString>
                
                

Si veda anche

ST_AsSVG, ST_AsGML


Name

ST_AsLatLonText — Return the Degrees, Minutes, Seconds representation of the given point.

Synopsis

text ST_AsLatLonText(geometry pt, text format='');

Descrizione

Returns the Degrees, Minutes, Seconds representation of the point.

[Note]

It is assumed the point is in a lat/lon projection. The X (lon) and Y (lat) coordinates are normalized in the output to the "normal" range (-180 to +180 for lon, -90 to +90 for lat).

The text parameter is a format string containing the format for the resulting text, similar to a date format string. Valid tokens are "D" for degrees, "M" for minutes, "S" for seconds, and "C" for cardinal direction (NSEW). DMS tokens may be repeated to indicate desired width and precision ("SSS.SSSS" means " 1.0023").

"M", "S", and "C" are optional. If "C" is omitted, degrees are shown with a "-" sign if south or west. If "S" is omitted, minutes will be shown as decimal with as many digits of precision as you specify. If "M" is also omitted, degrees are shown as decimal with as many digits precision as you specify.

If the format string is omitted (or zero-length) a default format will be used.

Availability: 2.0

Esempi

Default format.

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)'));
      st_aslatlontext       
----------------------------
 2°19'29.928"S 3°14'3.243"W

Providing a format (same as the default).

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D°M''S.SSS"C'));
      st_aslatlontext       
----------------------------
 2°19'29.928"S 3°14'3.243"W

Characters other than D, M, S, C and . are just passed through.

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D degrees, M minutes, S seconds to the C'));
                                   st_aslatlontext                                    
--------------------------------------------------------------------------------------
 2 degrees, 19 minutes, 30 seconds to the S 3 degrees, 14 minutes, 3 seconds to the W

Signed degrees instead of cardinal directions.

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D°M''S.SSS"'));
      st_aslatlontext       
----------------------------
 -2°19'29.928" -3°14'3.243"

Decimal degrees.

SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D.DDDD degrees C'));
          st_aslatlontext          
-----------------------------------
 2.3250 degrees S 3.2342 degrees W

Excessively large values are normalized.

SELECT (ST_AsLatLonText('POINT (-302.2342342 -792.32498)'));
        st_aslatlontext        
-------------------------------
 72°19'29.928"S 57°45'56.757"E

Name

ST_AsSVG — Transform a geometry into the coordinate space of a Mapbox Vector Tile.

Synopsis

text ST_AsHEXEWKB(geometry g1, text NDRorXDR);

text ST_AsHEXEWKB(geometry g1);

Descrizione

Transform a geometry into the coordinate space of a Mapbox Vector Tile of a set of rows corresponding to a Layer. Makes best effort to keep and even correct validity and might collapse geometry into a lower dimension in the process.

geom is the geometry to transform.

bounds is the geometric bounds of the tile contents without buffer.

extent is the tile extent in tile coordinate space as defined by the specification. If NULL it will default to 4096.

buffer is the buffer distance in tile coordinate space to optionally clip geometries. If NULL it will default to 256.

clip_geom is a boolean to control if geometries should be clipped or encoded as is. If NULL it will default to true.

Disponibilità: 1.4.0

[Note]

From 3.0, Wagyu can be chosen at configure time to clip and validate MVT polygons. This library is faster and produces more correct results than the GEOS default, but it might drop small polygons.

Esempi

SELECT ST_AsText(ST_AsMVTGeom(
        ST_GeomFromText('POLYGON ((0 0, 10 0, 10 5, 0 -5, 0 0))'),
        ST_MakeBox2D(ST_Point(0, 0), ST_Point(4096, 4096)),
        4096, 0, false));
                              st_astext
--------------------------------------------------------------------
 MULTIPOLYGON(((5 4096,10 4091,10 4096,5 4096)),((5 4096,0 4101,0 4096,5 4096)))

                
                

Name

ST_AsGML — Aggregate function returning a Mapbox Vector Tile representation of a set of rows.

Synopsis

text ST_AsKML(geometry geom, integer maxdecimaldigits=15);

text ST_AsKML(geography geog, integer maxdecimaldigits=15);

text ST_AsKML(integer version, geometry geom, integer maxdecimaldigits=15, text nprefix=NULL);

text ST_AsKML(integer version, geography geog, integer maxdecimaldigits=15, text nprefix=NULL);

Descrizione

An aggregate function which returns a binary Mapbox Vector Tile representation of a set of rows corresponding to a tile layer. The rows should contain a geometry column which will be encoded as a feature geometry. The geometry should be in tile coordinate space and valid as per the MVT specification. ST_AsSVG can be used to transform geometry into tile coordinate space. Other row columns are encoded as feature attributes.

The Mapbox Vector Tile format can store features with varying sets of attributes. To use this capability supply a JSONB column in the row data containing Json objects one level deep. The keys and values in the JSONB values will be encoded as feature attributes.

Tiles with multiple layers can be created by concatenating multiple calls to this function using ||.

[Important]

Do not call with a GEOMETRYCOLLECTION as an element in the row. However you can use ST_AsSVG to prepare a geometry collection for inclusion.

row row data with at least a geometry column.

name is the name of the layer. Default is the string "default".

extent is the tile extent in screen space as defined by the specification. Default is 4096.

geom_name is the name of the geometry column in the row data. Default is the first geometry column.

feature_id_name is the name of the Feature ID column in the row data. If NULL or negative the Feature ID is not set. The first column matching name and valid type (smallint, integer, bigint) will be used as Feature ID, and any subsequent column will be added as a property. JSON properties are not supported.

Enhanced: 3.0 - added support for Feature ID.

Enhanced: 2.5.0 - added support parallel query.

Disponibilità: 1.4.0

Esempi

WITH mvtgeom AS
(
  SELECT ST_AsMVTGeom(geom, ST_TileEnvelope(12, 513, 412), extent => 4096, buffer => 64) AS geom, name, description
  FROM points_of_interest
  WHERE geom && ST_TileEnvelope(12, 513, 412, margin => (64.0 / 4096))
)
SELECT ST_AsMVT(mvtgeom.*)
FROM mvtgeom;

Si veda anche

ST_AsSVG, ST_AsGML


Name

ST_AsSVG — Returns SVG path data for a geometry.

Synopsis

text ST_AsSVG(geometry geom, integer rel=0, integer maxdecimaldigits=15);

text ST_AsSVG(geography geog, integer rel=0, integer maxdecimaldigits=15);

Descrizione

Return the geometry as Scalar Vector Graphics (SVG) path data. Use 1 as second argument to have the path data implemented in terms of relative moves, the default (or 0) uses absolute moves. Third argument may be used to reduce the maximum number of decimal digits used in output (defaults to 15). Point geometries will be rendered as cx/cy when 'rel' arg is 0, x/y when 'rel' is 1. Multipoint geometries are delimited by commas (","), GeometryCollection geometries are delimited by semicolons (";").

[Note]

Availability: 1.2.2. Availability: 1.4.0 Changed in PostGIS 1.4.0 to include L command in absolute path to conform to http://www.w3.org/TR/SVG/paths.html#PathDataBNF

Changed: 2.0.0 to use default args and support named args

Esempi

SELECT ST_AsSVG(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

                st_assvg
                --------
                M 0 0 L 0 -1 1 -1 1 0 Z

Name

ST_AsTWKB — Returns the geometry as TWKB, aka "Tiny Well-Known Binary"

Synopsis

bytea ST_AsTWKB(geometry g1, integer decimaldigits_xy=0, integer decimaldigits_z=0, integer decimaldigits_m=0, boolean include_sizes=false, boolean include_bounding boxes=false);

bytea ST_AsTWKB(geometry[] geometries, bigint[] unique_ids, integer decimaldigits_xy=0, integer decimaldigits_z=0, integer decimaldigits_m=0, boolean include_sizes=false, boolean include_bounding_boxes=false);

Descrizione

Returns the geometry in TWKB (Tiny Well-Known Binary) format. TWKB is a compressed binary format with a focus on minimizing the size of the output.

The decimal digits parameters control how much precision is stored in the output. By default, values are rounded to the nearest unit before encoding. If you want to transfer more precision, increase the number. For example, a value of 1 implies that the first digit to the right of the decimal point will be preserved.

The sizes and bounding boxes parameters control whether optional information about the encoded length of the object and the bounds of the object are included in the output. By default they are not. Do not turn them on unless your client software has a use for them, as they just use up space (and saving space is the point of TWKB).

The array-input form of the function is used to convert a collection of geometries and unique identifiers into a TWKB collection that preserves the identifiers. This is useful for clients that expect to unpack a collection and then access further information about the objects inside. You can create the arrays using the array_agg function. The other parameters operate the same as for the simple form of the function.

[Note]

The format specification is available online at https://github.com/TWKB/Specification, and code for building a JavaScript client can be found at https://github.com/TWKB/twkb.js.

Enhanced: 2.4.0 memory and speed improvements.

Availability: 2.2.0

Esempi

SELECT ST_AsTWKB('LINESTRING(1 1,5 5)'::geometry);
                 st_astwkb
--------------------------------------------
\x02000202020808

To create an aggregate TWKB object including identifiers aggregate the desired geometries and objects first, using "array_agg()", then call the appropriate TWKB function.

SELECT ST_AsTWKB(array_agg(geom), array_agg(gid)) FROM mytable;
                 st_astwkb
--------------------------------------------
\x040402020400000202

Name

ST_AsX3D — Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML

Synopsis

text ST_AsX3D(geometry g1, integer maxdecimaldigits=15, integer options=0);

Descrizione

Returns a geometry as an X3D xml formatted node element http://www.web3d.org/standards/number/19776-1. If maxdecimaldigits (precision) is not specified then defaults to 15.

[Note]

There are various options for translating PostGIS geometries to X3D since X3D geometry types don't map directly to PostGIS geometry types and some newer X3D types that might be better mappings we have avoided since most rendering tools don't currently support them. These are the mappings we have settled on. Feel free to post a bug ticket if you have thoughts on the idea or ways we can allow people to denote their preferred mappings.

Below is how we currently map PostGIS 2D/3D types to X3D types

The 'options' argument is a bitfield. For PostGIS 2.2+, this is used to denote whether to represent coordinates with X3D GeoCoordinates Geospatial node and also whether to flip the x/y axis. By default, ST_AsX3D outputs in database form (long,lat or X,Y), but X3D default of lat/lon, y/x may be preferred.

  • 0: X/Y in database order (e.g. long/lat = X,Y is standard database order), default value, and non-spatial coordinates (just regular old Coordinate tag).

  • 1: Flip X and Y. If used in conjunction with the GeoCoordinate option switch, then output will be default "latitude_first" and coordinates will be flipped as well.

  • 2: Output coordinates in GeoSpatial GeoCoordinates. This option will throw an error if geometries are not in WGS 84 long lat (srid: 4326). This is currently the only GeoCoordinate type supported. Refer to X3D specs specifying a spatial reference system.. Default output will be GeoCoordinate geoSystem='"GD" "WE" "longitude_first"'. If you prefer the X3D default of GeoCoordinate geoSystem='"GD" "WE" "latitude_first"' use (2 + 1) = 3

PostGIS Type2D X3D Type3D X3D Type
LINESTRINGnot yet implemented - will be PolyLine2DLineSet
MULTILINESTRINGnot yet implemented - will be PolyLine2DIndexedLineSet
MULTIPOINTPolypoint2DPointSet
POINToutputs the space delimited coordinatesoutputs the space delimited coordinates
(MULTI) POLYGON, POLYHEDRALSURFACEInvalid X3D markupIndexedFaceSet (inner rings currently output as another faceset)
TINTriangleSet2D (Not Yet Implemented)IndexedTriangleSet
[Note]

2D geometry support not yet complete. Inner rings currently just drawn as separate polygons. We are working on these.

Lots of advancements happening in 3D space particularly with X3D Integration with HTML5

There is also a nice open source X3D viewer you can use to view rendered geometries. Free Wrl http://freewrl.sourceforge.net/ binaries available for Mac, Linux, and Windows. Use the FreeWRL_Launcher packaged to view the geometries.

Also check out PostGIS minimalist X3D viewer that utilizes this function and x3dDom html/js open source toolkit.

Availability: 2.0.0: ISO-IEC-19776-1.2-X3DEncodings-XML

Enhanced: 2.2.0: Support for GeoCoordinates and axis (x/y, long/lat) flipping. Look at options for details.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Example: Create a fully functional X3D document - This will generate a cube that is viewable in FreeWrl and other X3D viewers.

SELECT '<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d-3.0.dtd">
<X3D>
  <Scene>
    <Transform>
      <Shape>
       <Appearance>
            <Material emissiveColor=''0 0 1''/>   
       </Appearance
> ' || 
       ST_AsX3D( ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), 
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), 
((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), 
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ||
      '</Shape>
    </Transform>
  </Scene>
</X3D
>' As x3ddoc;

                x3ddoc
                --------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d-3.0.dtd">
<X3D>
  <Scene>
    <Transform>
      <Shape>
       <Appearance>
            <Material emissiveColor='0 0 1'/>   
       </Appearance
> 
       <IndexedFaceSet  coordIndex='0 1 2 3 -1 4 5 6 7 -1 8 9 10 11 -1 12 13 14 15 -1 16 17 18 19 -1 20 21 22 23'>
            <Coordinate point='0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 0 0 1 1 1 0 1 1 1 1 0 1 1 0 0 0 1 0 0 1 1 1 1 1 1 1 0 0 0 1 1 0 1 1 1 1 0 1 1' />
      </IndexedFaceSet>
      </Shape>
    </Transform>
  </Scene>
</X3D
>

Example: An Octagon elevated 3 Units and decimal precision of 6

SELECT ST_AsX3D(
ST_Translate(
    ST_Force_3d(
        ST_Buffer(ST_Point(10,10),5, 'quad_segs=2')), 0,0,
    3)
  ,6) As x3dfrag;

x3dfrag
--------
<IndexedFaceSet coordIndex="0 1 2 3 4 5 6 7">
    <Coordinate point="15 10 3 13.535534 6.464466 3 10 5 3 6.464466 6.464466 3 5 10 3 6.464466 13.535534 3 10 15 3 13.535534 13.535534 3 " />
</IndexedFaceSet
>

Esempio: TIN

SELECT ST_AsX3D(ST_GeomFromEWKT('TIN (((
                0 0 0, 
                0 0 1, 
                0 1 0, 
                0 0 0
            )), ((
                0 0 0, 
                0 1 0, 
                1 1 0, 
                0 0 0
            ))
            )')) As x3dfrag;

                x3dfrag
                --------
<IndexedTriangleSet  index='0 1 2 3 4 5'
><Coordinate point='0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 1 0'/></IndexedTriangleSet
>

Example: Closed multilinestring (the boundary of a polygon with holes)

SELECT ST_AsX3D(
                    ST_GeomFromEWKT('MULTILINESTRING((20 0 10,16 -12 10,0 -16 10,-12 -12 10,-20 0 10,-12 16 10,0 24 10,16 16 10,20 0 10),
  (12 0 10,8 8 10,0 12 10,-8 8 10,-8 0 10,-8 -4 10,0 -8 10,8 -4 10,12 0 10))') 
) As x3dfrag;

                x3dfrag
                --------
<IndexedLineSet  coordIndex='0 1 2 3 4 5 6 7 0 -1 8 9 10 11 12 13 14 15 8'>
    <Coordinate point='20 0 10 16 -12 10 0 -16 10 -12 -12 10 -20 0 10 -12 16 10 0 24 10 16 16 10 12 0 10 8 8 10 0 12 10 -8 8 10 -8 0 10 -8 -4 10 0 -8 10 8 -4 10 ' />
 </IndexedLineSet
>

Name

ST_GeoHash — Return a GeoHash representation of the geometry.

Synopsis

text ST_GeoHash(geometry geom, integer maxchars=full_precision_of_point);

Descrizione

Return a GeoHash representation (http://en.wikipedia.org/wiki/Geohash) of the geometry. A GeoHash encodes a point into a text form that is sortable and searchable based on prefixing. A shorter GeoHash is a less precise representation of a point. It can also be thought of as a box, that contains the actual point.

If no maxchars is specified ST_GeoHash returns a GeoHash based on full precision of the input geometry type. Points return a GeoHash with 20 characters of precision (about enough to hold the full double precision of the input). Other types return a GeoHash with a variable amount of precision, based on the size of the feature. Larger features are represented with less precision, smaller features with more precision. The idea is that the box implied by the GeoHash will always contain the input feature.

If maxchars is specified ST_GeoHash returns a GeoHash with at most that many characters so a possibly lower precision representation of the input geometry. For non-points, the starting point of the calculation is the center of the bounding box of the geometry.

Disponibilità: 1.4.0

[Note]

ST_GeoHash will not work with geometries that are not in geographic (lon/lat) coordinates.

This method supports Circular Strings and Curves

Esempi

SELECT ST_GeoHash(ST_SetSRID(ST_MakePoint(-126,48),4326));

         st_geohash
----------------------
 c0w3hf1s70w3hf1s70w3

SELECT ST_GeoHash(ST_SetSRID(ST_MakePoint(-126,48),4326),5);

 st_geohash
------------
 c0w3h
                
                

Si veda anche

ST_GeomFromGeoHash

8.10. Operatori

8.10.1. Bounding Box Operators

&& — Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
&&(geometry,box2df) — Returns TRUE if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).
&&(box2df,geometry) — Returns TRUE if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.
&&(box2df,box2df) — Returns TRUE if two 2D float precision bounding boxes (BOX2DF) intersect each other.
&&& — Returns TRUE if A's n-D bounding box intersects B's n-D bounding box.
&&& — Returns TRUE if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).
&&& — Returns TRUE if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.
&&& — Returns TRUE if two n-D float precision bounding boxes (GIDX) intersect each other.
&< — Returns TRUE if A's bounding box overlaps or is to the left of B's.
&<| — Returns TRUE if A's bounding box overlaps or is below B's.
&> — Returns TRUE if A' bounding box overlaps or is to the right of B's.
<< — Returns TRUE if A's bounding box is strictly to the left of B's.
<<| — Returns TRUE if A's bounding box is strictly below B's.
= — Returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.
>> — Returns TRUE if A's bounding box is strictly to the right of B's.
@ — Returns TRUE if A's bounding box is contained by B's.
@(geometry,box2df) — Returns TRUE if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).
@(box2df,geometry) — Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.
@(box2df,box2df) — Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.
|&> — Returns TRUE if A's bounding box overlaps or is above B's.
|>> — Returns TRUE if A's bounding box is strictly above B's.
~ — Returns TRUE if A's bounding box contains B's.
~(geometry,box2df) — Returns TRUE if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).
~(box2df,geometry) — Returns TRUE if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.
~(box2df,box2df) — Returns TRUE if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).
~= — Returns TRUE if A's bounding box is the same as B's.

Name

&& — Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.

Synopsis

boolean &&( geometry A , geometry B );

boolean &&( geography A , geography B );

Descrizione

The && operator returns TRUE if the 2D bounding box of geometry A intersects the 2D bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.5.0 support for geography was introduced.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 && tbl2.column2 AS overlaps
FROM ( VALUES
        (1, 'LINESTRING(0 0, 3 3)'::geometry),
        (2, 'LINESTRING(0 1, 0 5)'::geometry)) AS tbl1,
( VALUES
        (3, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

 column1 | column1 | overlaps
---------+---------+----------
           1 |       3 | t
           2 |       3 | f
(2 rows)

Si veda anche

ST_Intersects, &>, &<|, &<, ~, @


Name

&&(geometry,box2df) — Returns TRUE if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The && operator returns TRUE if the cached 2D bounding box of geometry A intersects the 2D bounding box B, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_Point(1,1) && ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) AS overlaps;

 overlaps
----------
 t
(1 row)

Name

&&(box2df,geometry) — Returns TRUE if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The && operator returns TRUE if the 2D bounding box A intersects the cached 2D bounding box of geometry B, using float precision. This means that if A is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) && ST_Point(1,1) AS overlaps;

 overlaps
----------
 t
(1 row)

Name

&&(box2df,box2df) — Returns TRUE if two 2D float precision bounding boxes (BOX2DF) intersect each other.

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The && operator returns TRUE if two 2D bounding boxes A and B intersect each other, using float precision. This means that if A (or B) is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) && ST_MakeBox2D(ST_Point(1,1), ST_Point(3,3)) AS overlaps;

 overlaps
----------
 t
(1 row)

Si veda anche

&&(geometry,box2df), &>, &<|, &<, ~, @


Name

&&& — Returns TRUE if A's n-D bounding box intersects B's n-D bounding box.

Synopsis

boolean &&&( geometry A , geometry B );

Descrizione

The &&& operator returns TRUE if the n-D bounding box of geometry A intersects the n-D bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Disponibilità: 2.0

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Examples: 3D LineStrings

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3d, 
                                    tbl1.column2 && tbl2.column2 AS overlaps_2d
FROM ( VALUES
        (1, 'LINESTRING Z(0 0 1, 3 3 2)'::geometry),
        (2, 'LINESTRING Z(1 2 0, 0 5 -1)'::geometry)) AS tbl1,
( VALUES
        (3, 'LINESTRING Z(1 2 1, 4 6 1)'::geometry)) AS tbl2;

 column1 | column1 | overlaps_3d | overlaps_2d
---------+---------+-------------+-------------
       1 |       3 | t           | t
       2 |       3 | f           | t

Examples: 3M LineStrings

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3zm, 
                                    tbl1.column2 && tbl2.column2 AS overlaps_2d
FROM ( VALUES
        (1, 'LINESTRING M(0 0 1, 3 3 2)'::geometry),
        (2, 'LINESTRING M(1 2 0, 0 5 -1)'::geometry)) AS tbl1,
( VALUES
        (3, 'LINESTRING M(1 2 1, 4 6 1)'::geometry)) AS tbl2;

 column1 | column1 | overlaps_3zm | overlaps_2d
---------+---------+-------------+-------------
       1 |       3 | t           | t
       2 |       3 | f           | t

Si veda anche

&&


Name

&&& — Returns TRUE if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The &&& operator returns TRUE if the cached n-D bounding box of geometry A intersects the n-D bounding box B, using float precision. This means that if B is a (double precision) box3d, it will be internally converted to a float precision 3D bounding box (GIDX)

[Note]

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_MakePoint(1,1,1) &&& ST_3DMakeBox(ST_MakePoint(0,0,0), ST_MakePoint(2,2,2)) AS overlaps;

 overlaps
----------
 t
(1 row)

Si veda anche

&&&, &&


Name

&&& — Returns TRUE if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The &&& operator returns TRUE if the n-D bounding box A intersects the cached n-D bounding box of geometry B, using float precision. This means that if A is a (double precision) box3d, it will be internally converted to a float precision 3D bounding box (GIDX)

[Note]

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_3DMakeBox(ST_MakePoint(0,0,0), ST_MakePoint(2,2,2)) &&& ST_MakePoint(1,1,1) AS overlaps;

 overlaps
----------
 t
(1 row)

Si veda anche

&&&, &&


Name

&&& — Returns TRUE if two n-D float precision bounding boxes (GIDX) intersect each other.

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The &&& operator returns TRUE if two n-D bounding boxes A and B intersect each other, using float precision. This means that if A (or B) is a (double precision) box3d, it will be internally converted to a float precision 3D bounding box (GIDX)

[Note]

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

Esempi

SELECT ST_3DMakeBox(ST_MakePoint(0,0,0), ST_MakePoint(2,2,2)) &&& ST_3DMakeBox(ST_MakePoint(1,1,1), ST_MakePoint(3,3,3)) AS overlaps;

 overlaps
----------
 t
(1 row)

Si veda anche

&&&, &&


Name

&< — Returns TRUE if A's bounding box overlaps or is to the left of B's.

Synopsis

boolean &<( geometry A , geometry B );

Descrizione

The &< operator returns TRUE if the bounding box of geometry A overlaps or is to the left of the bounding box of geometry B, or more accurately, overlaps or is NOT to the right of the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &< tbl2.column2 AS overleft
FROM
  ( VALUES
        (1, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING(0 0, 3 3)'::geometry),
        (3, 'LINESTRING(0 1, 0 5)'::geometry),
        (4, 'LINESTRING(6 0, 6 1)'::geometry)) AS tbl2;

 column1 | column1 | overleft
---------+---------+----------
           1 |       2 | f
           1 |       3 | f
           1 |       4 | t
(3 rows)

Si veda anche

&&, |&>, &>, &<|


Name

&<| — Returns TRUE if A's bounding box overlaps or is below B's.

Synopsis

boolean &<|( geometry A , geometry B );

Descrizione

The &<| operator returns TRUE if the bounding box of geometry A overlaps or is below of the bounding box of geometry B, or more accurately, overlaps or is NOT above the bounding box of geometry B.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &<| tbl2.column2 AS overbelow
FROM
  ( VALUES
        (1, 'LINESTRING(6 0, 6 4)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING(0 0, 3 3)'::geometry),
        (3, 'LINESTRING(0 1, 0 5)'::geometry),
        (4, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

 column1 | column1 | overbelow
---------+---------+-----------
           1 |       2 | f
           1 |       3 | t
           1 |       4 | t
(3 rows)

Si veda anche

&&, |&>, &>, &<


Name

&> — Returns TRUE if A' bounding box overlaps or is to the right of B's.

Synopsis

boolean &>( geometry A , geometry B );

Descrizione

The &> operator returns TRUE if the bounding box of geometry A overlaps or is to the right of the bounding box of geometry B, or more accurately, overlaps or is NOT to the left of the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &> tbl2.column2 AS overright
FROM
  ( VALUES
        (1, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING(0 0, 3 3)'::geometry),
        (3, 'LINESTRING(0 1, 0 5)'::geometry),
        (4, 'LINESTRING(6 0, 6 1)'::geometry)) AS tbl2;

 column1 | column1 | overright
---------+---------+-----------
           1 |       2 | t
           1 |       3 | t
           1 |       4 | f
(3 rows)

Si veda anche

&&, |&>, &<|, &<


Name

<< — Returns TRUE if A's bounding box is strictly to the left of B's.

Synopsis

boolean <<( geometry A , geometry B );

Descrizione

The << operator returns TRUE if the bounding box of geometry A is strictly to the left of the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 << tbl2.column2 AS left
FROM
  ( VALUES
        (1, 'LINESTRING (1 2, 1 5)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING (0 0, 4 3)'::geometry),
        (3, 'LINESTRING (6 0, 6 5)'::geometry),
        (4, 'LINESTRING (2 2, 5 6)'::geometry)) AS tbl2;

 column1 | column1 | left
---------+---------+------
           1 |       2 | f
           1 |       3 | t
           1 |       4 | t
(3 rows)

Si veda anche

>>, |>>, <<|


Name

<<| — Returns TRUE if A's bounding box is strictly below B's.

Synopsis

boolean <<|( geometry A , geometry B );

Descrizione

The <<| operator returns TRUE if the bounding box of geometry A is strictly below the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 <<| tbl2.column2 AS below
FROM
  ( VALUES
        (1, 'LINESTRING (0 0, 4 3)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING (1 4, 1 7)'::geometry),
        (3, 'LINESTRING (6 1, 6 5)'::geometry),
        (4, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl2;

 column1 | column1 | below
---------+---------+-------
           1 |       2 | t
           1 |       3 | f
           1 |       4 | f
(3 rows)

Si veda anche

<<, >>, |>>


Name

= — Returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.

Synopsis

boolean =( geometry A , geometry B );

boolean =( geography A , geography B );

Descrizione

The = operator returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B. PostgreSQL uses the =, <, and > operators defined for geometries to perform internal orderings and comparison of geometries (ie. in a GROUP BY or ORDER BY clause).

[Note]

Only geometry/geography that are exactly equal in all respects, with the same coordinates, in the same order, are considered equal by this operator. For "spatial equality", that ignores things like coordinate order, and can detect features that cover the same spatial area with different representations, use ST_OrderingEquals or ST_Equals

[Caution]

This operand will NOT make use of any indexes that may be available on the geometries. For an index assisted exact equality test, combine = with &&.

Changed: 2.4.0, in prior versions this was bounding box equality not a geometric equality. If you need bounding box equality, use ~= instead.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT 'LINESTRING(0 0, 0 1, 1 0)'::geometry = 'LINESTRING(1 1, 0 0)'::geometry;
 ?column?
----------
 t
(1 row)

SELECT ST_AsText(column1)
FROM ( VALUES
        ('LINESTRING(0 0, 1 1)'::geometry),
        ('LINESTRING(1 1, 0 0)'::geometry)) AS foo;
          st_astext
---------------------
 LINESTRING(0 0,1 1)
 LINESTRING(1 1,0 0)
(2 rows)

-- Nota: il GROUP BY usa lo "=" per confrontare l'equivalenza delle geometrie
SELECT ST_AsText(column1)
FROM ( VALUES
        ('LINESTRING(0 0, 1 1)'::geometry),
        ('LINESTRING(1 1, 0 0)'::geometry)) AS foo
GROUP BY column1;
          st_astext
---------------------
 LINESTRING(0 0,1 1)
(1 row)

-- In versions prior to 2.0, this used to return true --
 SELECT ST_GeomFromText('POINT(1707296.37 4820536.77)') =
        ST_GeomFromText('POINT(1707296.27 4820536.87)') As pt_intersect;
        
--pt_intersect --
f

Si veda anche

ST_Equals, ST_OrderingEquals, =


Name

>> — Returns TRUE if A's bounding box is strictly to the right of B's.

Synopsis

boolean >>( geometry A , geometry B );

Descrizione

The >> operator returns TRUE if the bounding box of geometry A is strictly to the right of the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 >> tbl2.column2 AS right
FROM
  ( VALUES
        (1, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING (1 4, 1 7)'::geometry),
        (3, 'LINESTRING (6 1, 6 5)'::geometry),
        (4, 'LINESTRING (0 0, 4 3)'::geometry)) AS tbl2;

 column1 | column1 | right
---------+---------+-------
           1 |       2 | t
           1 |       3 | f
           1 |       4 | f
(3 rows)

Si veda anche

<<, |>>, <<|


Name

@ — Returns TRUE if A's bounding box is contained by B's.

Synopsis

boolean @( geometry A , geometry B );

Descrizione

The @ operator returns TRUE if the bounding box of geometry A is completely contained by the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 @ tbl2.column2 AS contained
FROM
  ( VALUES
        (1, 'LINESTRING (1 1, 3 3)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING (0 0, 4 4)'::geometry),
        (3, 'LINESTRING (2 2, 4 4)'::geometry),
        (4, 'LINESTRING (1 1, 3 3)'::geometry)) AS tbl2;

 column1 | column1 | contained
---------+---------+-----------
           1 |       2 | t
           1 |       3 | f
           1 |       4 | t
(3 rows)

Si veda anche

~, &&


Name

@(geometry,box2df) — Returns TRUE if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).

Synopsis

boolean @( geometry A , geometry B );

Descrizione

The @ operator returns TRUE if the A geometry's 2D bounding box is contained the 2D bounding box B, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_Buffer(ST_GeomFromText('POINT(2 2)'), 1) @ ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) AS is_contained;

 is_contained
--------------
 t
(1 row)

Si veda anche

&&(geometry,box2df), &>, &<|, &<, ~, @


Name

@(box2df,geometry) — Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.

Synopsis

boolean @( geometry A , geometry B );

Descrizione

The @ operator returns TRUE if the 2D bounding box A is contained into the B geometry's 2D bounding box, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_MakeBox2D(ST_Point(2,2), ST_Point(3,3)) @ ST_Buffer(ST_GeomFromText('POINT(1 1)'), 10) AS is_contained;

 is_contained
--------------
 t
(1 row)

Si veda anche

&&(geometry,box2df), &>, &<|, &<, ~, @


Name

@(box2df,box2df) — Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.

Synopsis

boolean @( geometry A , geometry B );

Descrizione

The @ operator returns TRUE if the 2D bounding box A is contained into the 2D bounding box B, using float precision. This means that if A (or B) is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_MakeBox2D(ST_Point(2,2), ST_Point(3,3)) @ ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) AS is_contained;

 is_contained
--------------
 t
(1 row)

Si veda anche

&&(geometry,box2df), &>, &<|, &<, ~, @


Name

|&> — Returns TRUE if A's bounding box overlaps or is above B's.

Synopsis

boolean |&>( geometry A , geometry B );

Descrizione

The |&> operator returns TRUE if the bounding box of geometry A overlaps or is above the bounding box of geometry B, or more accurately, overlaps or is NOT below the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 |&> tbl2.column2 AS overabove
FROM
  ( VALUES
        (1, 'LINESTRING(6 0, 6 4)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING(0 0, 3 3)'::geometry),
        (3, 'LINESTRING(0 1, 0 5)'::geometry),
        (4, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

 column1 | column1 | overabove
---------+---------+-----------
           1 |       2 | t
           1 |       3 | f
           1 |       4 | f
(3 rows)

Si veda anche

&&, &>, &<|, &<


Name

|>> — Returns TRUE if A's bounding box is strictly above B's.

Synopsis

boolean |>>( geometry A , geometry B );

Descrizione

The |>> operator returns TRUE if the bounding box of geometry A is strictly above the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 |>> tbl2.column2 AS above
FROM
  ( VALUES
        (1, 'LINESTRING (1 4, 1 7)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING (0 0, 4 2)'::geometry),
        (3, 'LINESTRING (6 1, 6 5)'::geometry),
        (4, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl2;

 column1 | column1 | above
---------+---------+-------
           1 |       2 | t
           1 |       3 | f
           1 |       4 | f
(3 rows)

Si veda anche

<<, >>, <<|


Name

~ — Returns TRUE if A's bounding box contains B's.

Synopsis

boolean ~( geometry A , geometry B );

Descrizione

The ~ operator returns TRUE if the bounding box of geometry A completely contains the bounding box of geometry B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Esempi

SELECT tbl1.column1, tbl2.column1, tbl1.column2 ~ tbl2.column2 AS contains
FROM
  ( VALUES
        (1, 'LINESTRING (0 0, 3 3)'::geometry)) AS tbl1,
  ( VALUES
        (2, 'LINESTRING (0 0, 4 4)'::geometry),
        (3, 'LINESTRING (1 1, 2 2)'::geometry),
        (4, 'LINESTRING (0 0, 3 3)'::geometry)) AS tbl2;

 column1 | column1 | contains
---------+---------+----------
           1 |       2 | f
           1 |       3 | t
           1 |       4 | t
(3 rows)

Si veda anche

@, &&


Name

~(geometry,box2df) — Returns TRUE if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).

Synopsis

boolean ~( geometry A , geometry B );

Descrizione

The ~ operator returns TRUE if the 2D bounding box of a geometry A contains the 2D bounding box B, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_Buffer(ST_GeomFromText('POINT(1 1)'), 10) ~ ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) AS contains;

 contains
----------
 t
(1 row)

Name

~(box2df,geometry) — Returns TRUE if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.

Synopsis

boolean ~( geometry A , geometry B );

Descrizione

The ~ operator returns TRUE if the 2D bounding box A contains the B geometry's bounding box, using float precision. This means that if A is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) ~ ST_Buffer(ST_GeomFromText('POINT(2 2)'), 1) AS contains;

 contains
----------
 t
(1 row)

Name

~(box2df,box2df) — Returns TRUE if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).

Synopsis

boolean ~( geometry A , geometry B );

Descrizione

The ~ operator returns TRUE if the 2D bounding box A contains the 2D bounding box B, using float precision. This means that if A is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

[Note]

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves

This function supports Polyhedral surfaces.

Esempi

SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) ~ ST_MakeBox2D(ST_Point(2,2), ST_Point(3,3)) AS contains;

 contains
----------
 t
(1 row)

Si veda anche

&&(geometry,box2df), &>, &<|, &<, ~, @


Name

~= — Returns TRUE if A's bounding box is the same as B's.

Synopsis

boolean ~=( geometry A , geometry B );

Descrizione

The ~= operator returns TRUE if the bounding box of geometry/geography A is the same as the bounding box of geometry/geography B.

[Note]

This operand will make use of any indexes that may be available on the geometries.

Availability: 1.5.0 changed behavior

This function supports Polyhedral surfaces.

[Warning]

This operator has changed behavior in PostGIS 1.5 from testing for actual geometric equality to only checking for bounding box equality. To complicate things it also depends on if you have done a hard or soft upgrade which behavior your database has. To find out which behavior your database has you can run the query below. To check for true equality use ST_OrderingEquals or ST_Equals.

Esempi

select 'LINESTRING(0 0, 1 1)'::geometry ~= 'LINESTRING(0 1, 1 0)'::geometry as equality;
 equality   |
-----------------+
          t    |
                        

8.10.2. Operatori

<-> — Returns the 2D distance between A and B.
|=| — Returns the distance between A and B trajectories at their closest point of approach.
<#> — Returns the 2D distance between A and B bounding boxes.
<<->> — Returns the n-D distance between the centroids of A and B bounding boxes.
<<#>> — Returns the n-D distance between A and B bounding boxes.

Name

<-> — Returns the 2D distance between A and B.

Synopsis

double precision <->( geometry A , geometry B );

double precision <->( geography A , geography B );

Descrizione

The <-> operator returns the 2D distance between two geometries. Used in the "ORDER BY" clause provides index-assisted nearest-neighbor result sets. For PostgreSQL below 9.5 only gives centroid distance of bounding boxes and for PostgreSQL 9.5+, does true KNN distance search giving true distance between geometries, and distance sphere for geographies.

[Note]

This operand will make use of 2D GiST indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

[Note]

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;POINT(1011102 450541)'::geometry instead of a.geom

Refer to PostGIS workshop: Nearest-Neighbour Searching for a detailed example.

Enhanced: 2.2.0 -- True KNN ("K nearest neighbor") behavior for geometry and geography for PostgreSQL 9.5+. Note for geography KNN is based on sphere rather than spheroid. For PostgreSQL 9.4 and below, geography support is new but only supports centroid box.

Changed: 2.2.0 -- For PostgreSQL 9.5 users, old Hybrid syntax may be slower, so you'll want to get rid of that hack if you are running your code only on PostGIS 2.2+ 9.5+. See examples below.

Availability: 2.0.0 -- Weak KNN provides nearest neighbors based on geometry centroid distances instead of true distances. Exact results for points, inexact for all other types. Available for PostgreSQL 9.1+

Esempi

SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr 
FROM va2005 
ORDER BY d limit 10;

        d         | edabbr | vaabbr
------------------+--------+--------
                0 | ALQ    | 128
 5541.57712511724 | ALQ    | 129A
 5579.67450712005 | ALQ    | 001
  6083.4207708641 | ALQ    | 131
  7691.2205404848 | ALQ    | 003
 7900.75451037313 | ALQ    | 122
 8694.20710669982 | ALQ    | 129B
 9564.24289057111 | ALQ    | 130
  12089.665931705 | ALQ    | 127
 18472.5531479404 | ALQ    | 002
(10 rows)

Then the KNN raw answer:

SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr 
FROM va2005 
ORDER BY d limit 10;

        d         | edabbr | vaabbr
------------------+--------+--------
                0 | ALQ    | 128
 5541.57712511724 | ALQ    | 129A
 5579.67450712005 | ALQ    | 001
  6083.4207708641 | ALQ    | 131
  7691.2205404848 | ALQ    | 003
 7900.75451037313 | ALQ    | 122
 8694.20710669982 | ALQ    | 129B
 9564.24289057111 | ALQ    | 130
  12089.665931705 | ALQ    | 127
 18472.5531479404 | ALQ    | 002
(10 rows)

If you run "EXPLAIN ANALYZE" on the two queries you would see a performance improvement for the second.

For users running with PostgreSQL < 9.5, use a hybrid query to find the true nearest neighbors. First a CTE query using the index-assisted KNN, then an exact query to get correct ordering:

WITH index_query AS (
  SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
          FROM va2005
  ORDER BY geom <-> 'SRID=3005;POINT(1011102 450541)'::geometry LIMIT 100) 
  SELECT * 
          FROM index_query 
  ORDER BY d limit 10;

        d         | edabbr | vaabbr
------------------+--------+--------
                0 | ALQ    | 128
 5541.57712511724 | ALQ    | 129A
 5579.67450712005 | ALQ    | 001
  6083.4207708641 | ALQ    | 131
  7691.2205404848 | ALQ    | 003
 7900.75451037313 | ALQ    | 122
 8694.20710669982 | ALQ    | 129B
 9564.24289057111 | ALQ    | 130
  12089.665931705 | ALQ    | 127
 18472.5531479404 | ALQ    | 002
(10 rows)

                        

Si veda anche

ST_DWithin, ST_Distance, <#>


Name

|=| — Returns the distance between A and B trajectories at their closest point of approach.

Synopsis

double precision |=|( geometry A , geometry B );

Descrizione

The |=| operator returns the 3D distance between two trajectories (See ST_IsValidTrajectory). This is the same as ST_DistanceCPA but as an operator it can be used for doing nearest neightbor searches using an N-dimensional index (requires PostgreSQL 9.5.0 or higher).

[Note]

This operand will make use of ND GiST indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

[Note]

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;LINESTRINGM(0 0 0,0 0 1)'::geometry instead of a.geom

Availability: 2.2.0. Index-supported only available for PostgreSQL 9.5+

Esempi

-- Save a literal query trajectory in a psql variable...
\set qt 'ST_AddMeasure(ST_MakeLine(ST_MakePointM(-350,300,0),ST_MakePointM(-410,490,0)),10,20)'
-- Run the query !
SELECT track_id, dist FROM (
  SELECT track_id, ST_DistanceCPA(tr,:qt) dist
  FROM trajectories
  ORDER BY tr |=| :qt
  LIMIT 5
) foo;
 track_id        dist
----------+-------------------
      395 | 0.576496831518066
      380 |  5.06797130410151
      390 |  7.72262293958322
      385 |   9.8004461358071
      405 |  10.9534397988433
(5 rows)

Name

<#> — Returns the 2D distance between A and B bounding boxes.

Synopsis

double precision <#>( geometry A , geometry B );

Descrizione

The <#> operator returns distance between two floating point bounding boxes, possibly reading them from a spatial index (PostgreSQL 9.1+ required). Useful for doing nearest neighbor approximate distance ordering.

[Note]

This operand will make use of any indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

[Note]

Index only kicks in if one of the geometries is a constant e.g. ORDER BY (ST_GeomFromText('POINT(1 2)') <#> geom) instead of g1.geom <#>.

Availability: 2.0.0 -- KNN only available for PostgreSQL 9.1+

Esempi

SELECT *
FROM (
SELECT b.tlid, b.mtfcc, 
        b.geom <#
> ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
                745787 2948499,745740 2948468,745712 2948438,
                745690 2948384,745677 2948319)',2249) As b_dist, 
                ST_Distance(b.geom, ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
                745787 2948499,745740 2948468,745712 2948438,
                745690 2948384,745677 2948319)',2249)) As act_dist
    FROM bos_roads As b 
    ORDER BY b_dist, b.tlid
    LIMIT 100) As foo
    ORDER BY act_dist, tlid LIMIT 10;

   tlid    | mtfcc |      b_dist      |     act_dist
-----------+-------+------------------+------------------
  85732027 | S1400 |                0 |                0
  85732029 | S1400 |                0 |                0
  85732031 | S1400 |                0 |                0
  85734335 | S1400 |                0 |                0
  85736037 | S1400 |                0 |                0
 624683742 | S1400 |                0 | 128.528874268666
  85719343 | S1400 | 260.839270432962 | 260.839270432962
  85741826 | S1400 | 164.759294123275 | 260.839270432962
  85732032 | S1400 |           277.75 | 311.830282365264
  85735592 | S1400 |           222.25 | 311.830282365264
(10 rows)

Si veda anche

ST_DWithin, ST_Distance, <->


Name

<<->> — Returns the n-D distance between the centroids of A and B bounding boxes.

Synopsis

double precision <<->>( geometry A , geometry B );

Descrizione

The <<->> operator returns the n-D (euclidean) distance between the centroids of the bounding boxes of two geometries. Useful for doing nearest neighbor approximate distance ordering.

[Note]

This operand will make use of n-D GiST indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

[Note]

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;POINT(1011102 450541)'::geometry instead of a.geom

Availability: 2.2.0 -- KNN only available for PostgreSQL 9.1+

Si veda anche

<<#>>, <->


Name

<<#>> — Returns the n-D distance between A and B bounding boxes.

Synopsis

double precision <<#>>( geometry A , geometry B );

Descrizione

The <<#>> operator returns distance between two floating point bounding boxes, possibly reading them from a spatial index (PostgreSQL 9.1+ required). Useful for doing nearest neighbor approximate distance ordering.

[Note]

This operand will make use of any indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

[Note]

Index only kicks in if one of the geometries is a constant e.g. ORDER BY (ST_GeomFromText('POINT(1 2)') <<#>> geom) instead of g1.geom <<#>>.

Availability: 2.2.0 -- KNN only available for PostgreSQL 9.1+

Si veda anche

<<->>, <#>

8.11. Spatial Relationships

Abstract

These functions determine spatial relationships between geometries.

8.11.1. Topological Relationships

ST_3DIntersects — Returns true if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area).
ST_Contains — Returns true if no points of B lie in the exterior of A, and A and B have at least one interior point in common.
ST_ContainsProperly — Returns true if B intersects the interior of A but not the boundary or exterior.
ST_CoveredBy — Returns true if no point in A is outside B
ST_Covers — Returns true if no point in B is outside A
ST_Crosses — Returns true if two geometries have some, but not all, interior points in common.
ST_LineCrossingDirection — Returns a number indicating the crossing behavior of two LineStrings.
ST_Disjoint — Returns true if two geometries do not intersect (they have no point in common).
ST_Equals — Returns true if two geometries include the same set of points.
ST_Intersects — Returns true if two geometries intersect (they have at least one point in common).
ST_OrderingEquals — Returns true if two geometries represent the same geometry and have points in the same directional order.
ST_Overlaps — Returns true if two geometries intersect and have the same dimension, but are not completely contained by each other.
ST_Relate — Tests if two geometries have a topological relationship matching an Intersection Matrix pattern, or computes their Intersection Matrix
ST_RelateMatch — Tests if a DE-9IM Intersection Matrix matches an Intersection Matrix pattern
ST_Touches — Returns true if two geometries have at least one point in common, but their interiors do not intersect.
ST_Within — Returns true if no points of A lie in the exterior of B, and A and B have at least one interior point in common.

Name

ST_3DIntersects — Returns true if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area).

Synopsis

boolean ST_3DIntersects( geometry geomA , geometry geomB );

Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Changed: 3.0.0 SFCGAL backend removed, GEOS backend supports TINs.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method is also provided by SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM 3: ?

Geometry Examples

SELECT ST_3DIntersects(pt, line), ST_Intersects(pt, line)
        FROM (SELECT 'POINT(0 0 2)'::geometry As pt, 'LINESTRING (0 0 1, 0 2 3)'::geometry As line) As foo;
 st_3dintersects | st_intersects
-----------------+---------------
 f               | t
(1 row)
                

TIN Examples

SELECT ST_3DIntersects('TIN(((0 0 0,1 0 0,0 1 0,0 0 0)))'::geometry, 'POINT(.1 .1 0)'::geometry);
 st_3dintersects
-----------------
 t

Name

ST_Contains — Returns true if no points of B lie in the exterior of A, and A and B have at least one interior point in common.

Synopsis

boolean ST_Contains(geometry geomA, geometry geomB);

Description

Returns TRUE if geometry B is completely inside geometry A. A contains B if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A.

A subtlety of the definition is that a geometry does not contain its boundary. This implies that polygons and lines do not contain lines and points lying in their boundary. For further details see Subtleties of OGC Covers, Contains, Within. (The ST_Covers predicate provides a more inclusive relationship.) However, a geometry does contain itself. (In contrast, in the ST_ContainsProperly predicate a geometry does not properly contain itself.)

ST_Contains is the inverse of ST_Within. So, ST_Contains(A,B) = ST_Within(B,A).

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function _ST_Contains.

Performed by the GEOS module

Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

[Important]

Do not use this function with invalid geometries. You will get unexpected results.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 - same as within(geometry B, geometry A)

This method implements the SQL/MM specification. SQL-MM 3: 5.1.31

Examples

The ST_Contains predicate returns TRUE in all the following illustrations.

LINESTRING / MULTIPOINT

POLYGON / POINT

POLYGON / LINESTRING

POLYGON / POLYGON

The ST_Contains predicate returns FALSE in all the following illustrations.

POLYGON / MULTIPOINT

POLYGON / LINESTRING

-- A circle within a circle
SELECT ST_Contains(smallc, bigc) As smallcontainsbig,
           ST_Contains(bigc,smallc) As bigcontainssmall,
           ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,
           ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
           ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
           ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
                         ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;

-- Result
  smallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | bigcontainsexterior
------------------+------------------+------------------+------------+-------------------+---------------------
 f                | t                | t                | t          | t        | f

-- Example demonstrating difference between contains and contains properly
SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
   ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
                         ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
                         ( ST_Point(1,1) )
          ) As foo(geomA);

  geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
--------------+------------+----------------+-------------+-----------------
ST_Polygon    | t          | f              | f           | f
ST_LineString | t          | f              | f           | f
ST_Point      | t          | t              | f           | f

 

Name

ST_ContainsProperly — Returns true if B intersects the interior of A but not the boundary or exterior.

Synopsis

boolean ST_ContainsProperly(geometry geomA, geometry geomB);

Description

Returns true if B intersects the interior of A but not the boundary or exterior.

A does not properly contain itself, but does contain itself.

Every point of the other geometry is a point of this geometry's interior. The DE-9IM Intersection Matrix for the two geometries matches [T**FF*FF*] used in ST_Relate

An example use case for this predicate is computing the intersections of a set of geometries with a large polygonal geometry. Since intersection is a fairly slow operation, it can be more efficient to use containsProperly to filter out test geometries which lie wholly inside the area. In these cases the intersection is known a priori to be exactly the original test geometry.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function _ST_ContainsProperly.

[Note]

The advantage of this predicate over ST_Contains and ST_Intersects is that it can be computed more efficiently, with no need to compute topology at individual points.

Performed by the GEOS module.

Availability: 1.4.0

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

[Important]

Do not use this function with invalid geometries. You will get unexpected results.

Examples

--a circle within a circle
        SELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,
        ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,
        ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,
        ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
        ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
        ST_ContainsProperly(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
        FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
        ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
        --Result
  smallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | bigcoversexterior | bigcontainsexterior
------------------+------------------+------------------+------------+-------------------+---------------------
 f                     | t                    | f                    | t          | t                 | f

 --example demonstrating difference between contains and contains properly
 SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
 ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
 FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
                  ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
                  ( ST_Point(1,1) )
        ) As foo(geomA);

  geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
--------------+------------+----------------+-------------+-----------------
ST_Polygon    | t          | f              | f           | f
ST_LineString | t          | f              | f           | f
ST_Point      | t          | t              | f           | f
 

Name

ST_CoveredBy — Returns true if no point in A is outside B

Synopsis

boolean ST_CoveredBy(geometry geomA, geometry geomB);

boolean ST_CoveredBy(geography geogA, geography geogB);

Description

Returns true if no point in Geometry/Geography A lies outside Geometry/Geography B. Equivalently, tests if every point of geometry A is inside (i.e. intersects the interior or boundary of) geometry B.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function _ST_CoveredBy.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

[Important]

Do not use this function with invalid geometries. You will get unexpected results.

Performed by the GEOS module

Availability: 1.2.2

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

Examples

--a circle coveredby a circle
SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
        ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
        ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
        ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
        ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
        --Result
 smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
--------------+-------------------+----------------------+------------------
 t            | t                 | t                    | f
(1 row)        

Name

ST_Covers — Returns true if no point in B is outside A

Synopsis

boolean ST_Covers(geometry geomA, geometry geomB);

boolean ST_Covers(geography geogpolyA, geography geogpointB);

Description

Returns true if no point in Geometry/Geography B is outside Geometry/Geography A. Equivalently, tests if every point of geometry B is inside (i.e. intersects the interior or boundary of) geometry A.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function _ST_Covers.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

[Important]

Do not use this function with invalid geometries. You will get unexpected results.

Performed by the GEOS module

Enhanced: 2.4.0 Support for polygon in polygon and line in polygon added for geography type

Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Availability: 1.5 - support for geography was introduced.

Availability: 1.2.2

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

Examples

Geometry example

--a circle covering a circle
SELECT ST_Covers(smallc,smallc) As smallinsmall,
        ST_Covers(smallc, bigc) As smallcoversbig,
        ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
        ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
        ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
        --Result
 smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior
--------------+----------------+-------------------+---------------------
 t            | f              | t                 | f
(1 row)        

Geeography Example

-- a point with a 300 meter buffer compared to a point, a point and its 10 meter buffer
SELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt,
        ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_cent
        FROM (SELECT ST_Buffer(ST_GeogFromText('SRID=4326;POINT(-99.327 31.4821)'), 300) As geog_poly,
                                ST_GeogFromText('SRID=4326;POINT(-99.33 31.483)') As geog_pt ) As foo;

 poly_covers_pt | buff_10m_covers_cent
----------------+------------------
 f              | t
                

Name

ST_Crosses — Returns true if two geometries have some, but not all, interior points in common.

Synopsis

boolean ST_Crosses(geometry g1, geometry g2);

Description

ST_Crosses takes two geometry objects and returns true if their intersection "spatially cross", that is, the geometries have some, but not all interior points in common. The intersection of the interiors of the geometries must not be the empty set and must have a dimensionality less than the maximum dimension of the two input geometries. Additionally, the intersection of the two geometries must not equal either of the source geometries. Otherwise, it returns false.

In mathematical terms, this is expressed as:

The DE-9IM Intersection Matrix for the two geometries is:

  • T*T****** (for Point/Line, Point/Area, and Line/Area situations)

  • T*****T** (for Line/Point, Area/Point, and Area/Line situations)

  • 0******** (for Line/Line situations)

For any other combination of dimensions this predicate returns false.

The OpenGIS Simple Features Specification defines this predicate only for Point/Line, Point/Area, Line/Line, and Line/Area situations. JTS / GEOS extends the definition to apply to Line/Point, Area/Point and Area/Line situations as well. This makes the relation symmetric.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.29

Examples

The following illustrations all return TRUE.

MULTIPOINT / LINESTRING

MULTIPOINT / POLYGON

LINESTRING / POLYGON

LINESTRING / LINESTRING

Consider a situation where a user has two tables: a table of roads and a table of highways.

CREATE TABLE roads (
  id serial NOT NULL,
  the_geom geometry,
  CONSTRAINT roads_pkey PRIMARY KEY (road_id)
);

CREATE TABLE highways (
  id serial NOT NULL,
  the_gem geometry,
  CONSTRAINT roads_pkey PRIMARY KEY (road_id)
);

To determine a list of roads that cross a highway, use a query similiar to:

SELECT roads.id
FROM roads, highways
WHERE ST_Crosses(roads.the_geom, highways.the_geom);

Name

ST_LineCrossingDirection — Returns a number indicating the crossing behavior of two LineStrings.

Synopsis

integer ST_LineCrossingDirection(geometry linestringA, geometry linestringB);

Description

Given 2 linestrings, returns an integer between -3 and 3 indicating what kind of crossing behavior exists between them. 0 indicates no crossing. This is only supported for LINESTRINGs.

The crossing number has the following meaning:

  • 0: LINE NO CROSS

  • -1: LINE CROSS LEFT

  • 1: LINE CROSS RIGHT

  • -2: LINE MULTICROSS END LEFT

  • 2: LINE MULTICROSS END RIGHT

  • -3: LINE MULTICROSS END SAME FIRST LEFT

  • 3: LINE MULTICROSS END SAME FIRST RIGHT

Availability: 1.4

Examples

Line 1 (green), Line 2 ball is start point, triangle are end points. Query below.

SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
          ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
SELECT
 ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
 ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As line2
        ) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
           3 |          -3
                                

Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.

SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
          ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
 SELECT
  ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
  ST_GeomFromText('LINESTRING (171 154, 20 140, 71 74, 2.99 90.16)') As line2
) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
           2 |          -2
                                

Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.

SELECT
        ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
        ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
 SELECT
  ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
  ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As line2
  ) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
          -1 |          1
                                

Line 1 (green), Line 2 (blue) ball is start point, triangle are end points. Query below.

SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
          ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (SELECT
        ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
        ST_GeomFromText('LINESTRING(2.99 90.16,71 74,20 140,171 154)') As line2
        ) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
          -2 |          2
                                

SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.the_geom, s2.the_geom)
        FROM streets s1 CROSS JOIN streets s2 ON (s1.gid != s2.gid AND s1.the_geom && s2.the_geom )
WHERE ST_CrossingDirection(s1.the_geom, s2.the_geom) > 0;

See Also

ST_Crosses


Name

ST_Disjoint — Returns true if two geometries do not intersect (they have no point in common).

Synopsis

boolean ST_Disjoint( geometry A , geometry B );

Description

Overlaps, Touches, Within all imply geometries are not spatially disjoint. If any of the aforementioned returns true, then the geometries are not spatially disjoint. Disjoint implies false for spatial intersection.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

Performed by the GEOS module

[Note]

This function call does not use indexes

[Note]

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 - a.Relate(b, 'FF*FF****')

This method implements the SQL/MM specification. SQL-MM 3: 5.1.26

Examples

SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
 st_disjoint
---------------
 t
(1 row)
SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
 st_disjoint
---------------
 f
(1 row)
                

Name

ST_Equals — Returns true if two geometries include the same set of points.

Synopsis

boolean ST_Equals(geometry A, geometry B);

Description

Returns TRUE if the given Geometries are "spatially equal". Use this for a 'better' answer than '='. Note by spatially equal we mean ST_Within(A,B) = true and ST_Within(B,A) = true and also mean ordering of points can be different but represent the same geometry structure. To verify the order of points is consistent, use ST_OrderingEquals (it must be noted ST_OrderingEquals is a little more stringent than simply verifying order of points are the same).

[Important]

This function will return false if either geometry is invalid except in the case where they are binary equal.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2

This method implements the SQL/MM specification. SQL-MM 3: 5.1.24

Changed: 2.2.0 Returns true even for invalid geometries if they are binary equal

Examples

SELECT ST_Equals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
                ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
 st_equals
-----------
 t
(1 row)

SELECT ST_Equals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
                ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
 st_equals
-----------
 t
(1 row)

Name

ST_Intersects — Returns true if two geometries intersect (they have at least one point in common).

Synopsis

boolean ST_Intersects( geometry geomA , geometry geomB );

boolean ST_Intersects( geography geogA , geography geogB );

Description

If a geometry or geography shares any portion of space then they intersect. For geography -- tolerance is 0.00001 meters (so any points that are close are considered to intersect)

ST_Overlaps, ST_Touches, ST_Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Changed: 3.0.0 SFCGAL version removed and native suppport for 2D TINS added.

Enhanced: 2.5.0 Supports GEOMETRYCOLLECTION.

Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Performed by the GEOS module (for geometry), geography is native

Availability: 1.5 support for geography was introduced.

[Note]

For geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather than spheroid calculation.

[Note]

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 - ST_Intersects(g1, g2 ) --> Not (ST_Disjoint(g1, g2 ))

This method implements the SQL/MM specification. SQL-MM 3: 5.1.27

This method supports Circular Strings and Curves

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Geometry Examples

SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
 st_intersects
---------------
 f
(1 row)
SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
 st_intersects
---------------
 t
(1 row)

-- Look up in table. Make sure table has a GiST index on geometry column for faster lookup.
SELECT id, name FROM cities WHERE ST_Intersects(geom, 'SRID=4326;POLYGON((28 53,27.707 52.293,27 52,26.293 52.293,26 53,26.293 53.707,27 54,27.707 53.707,28 53))');
 id | name
----+-------
  2 | Minsk
(1 row)

Geography Examples

SELECT ST_Intersects(
                'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)'::geography,
                'SRID=4326;POINT(-43.23456 72.4567772)'::geography
                );

 st_intersects
---------------
t

Name

ST_OrderingEquals — Returns true if two geometries represent the same geometry and have points in the same directional order.

Synopsis

boolean ST_OrderingEquals(geometry A, geometry B);

Description

ST_OrderingEquals compares two geometries and returns t (TRUE) if the geometries are equal and the coordinates are in the same order; otherwise it returns f (FALSE).

[Note]

This function is implemented as per the ArcSDE SQL specification rather than SQL-MM. http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals

This method implements the SQL/MM specification. SQL-MM 3: 5.1.43

Examples

SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
                ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
 st_orderingequals
-----------
 f
(1 row)

SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
                ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
 st_orderingequals
-----------
 t
(1 row)

SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
                ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
 st_orderingequals
-----------
 f
(1 row)

Name

ST_Overlaps — Returns true if two geometries intersect and have the same dimension, but are not completely contained by each other.

Synopsis

boolean ST_Overlaps(geometry A, geometry B);

Description

Returns TRUE if the Geometries "spatially overlap". By that we mean they intersect, but one does not completely contain another.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function _ST_Overlaps.

Performed by the GEOS module

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.32

Examples

The following illustrations all return TRUE.

MULTIPOINT / MULTIPOINT

LINESTRING / LINESTRING

POLYGON / POLYGON

--a point on a line is contained by the line and is of a lower dimension, and therefore does not overlap the line
                        nor crosses

SELECT ST_Overlaps(a,b) As a_overlap_b,
        ST_Crosses(a,b) As a_crosses_b,
                ST_Intersects(a, b) As a_intersects_b, ST_Contains(b,a) As b_contains_a
FROM (SELECT ST_GeomFromText('POINT(1 0.5)') As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
        As foo

a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a
------------+-------------+----------------+--------------
f           | f           | t              | t

--a line that is partly contained by circle, but not fully is defined as intersecting and crossing,
-- but since of different dimension it does not overlap
SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b,
        ST_Intersects(a, b) As a_intersects_b,
        ST_Contains(a,b) As a_contains_b
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
        As foo;

 a_overlap_b | a_crosses_b | a_intersects_b | a_contains_b
-------------+-------------+----------------+--------------
 f           | t           | t              | f

 -- a 2-dimensional bent hot dog (aka buffered line string) that intersects a circle,
 --        but is not fully contained by the circle is defined as overlapping since they are of the same dimension,
--        but it does not cross, because the intersection of the 2 is of the same dimension
--        as the maximum dimension of the 2

SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b, ST_Intersects(a, b) As a_intersects_b,
ST_Contains(b,a) As b_contains_a,
ST_Dimension(a) As dim_a, ST_Dimension(b) as dim_b, ST_Dimension(ST_Intersection(a,b)) As dima_intersection_b
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a,
        ST_Buffer(ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)'),0.5)  As b)
        As foo;

 a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a | dim_a | dim_b | dima_intersection_b
-------------+-------------+----------------+--------------+-------+-------+---------------------
 t           | f           | t              | f            |     2 |     2 |              2

Name

ST_Relate — Tests if two geometries have a topological relationship matching an Intersection Matrix pattern, or computes their Intersection Matrix

Synopsis

boolean ST_Relate(geometry geomA, geometry geomB, text intersectionMatrixPattern);

text ST_Relate(geometry geomA, geometry geomB);

text ST_Relate(geometry geomA, geometry geomB, integer boundaryNodeRule);

Description

These functions allow testing and evaluating the spatial (topological) relationship between two geometries, as defined by the Dimensionally Extended 9-Intersection Model (DE-9IM).

The DE-9IM is specified as a 9-element matrix indicating the dimension of the intersections between the Interior, Boundary and Exterior of two geometries. It is represented by a 9-character text string using the symbols 'F', '0', '1', '2' (e.g. 'FF1FF0102').

A specific kind of spatial relationships is evaluated by comparing the intersection matrix to an intersection matrix pattern. A pattern can include the additional symbols 'T' and '*'. Common spatial relationships are provided by the named functions ST_Contains, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Crosses, ST_Disjoint, ST_Equals, ST_Intersects, ST_Overlaps, ST_Touches, and ST_Within. Using an explicit pattern allows testing multiple conditions of intersects, crosses, etc in one step. It also allows testing spatial relationships which do not have a named spatial relationship function. For example, the relationship "Interior-Intersects" has the DE-9IM pattern T********, which is not evaluated by any named predicate.

For more information refer to Section 5.1, “Determining Spatial Relationships”.

Variant 1: Tests if two geometries are spatially related according to the given intersectionMatrixPattern.

[Note]

Unlike most of the named spatial relationship predicates, this does NOT automatically include an index call. The reason is that some relationships are true for geometries which do NOT intersect (e.g. Disjoint). If you are using a relationship pattern that requires intersection, then include the && index call.

[Note]

It is better to use a named relationship function if available, since they automatically use a spatial index where one exists. Also, they may implement performance optimizations which are not available with full relate evalation.

Variant 2: Returns the DE-9IM matrix string for the spatial relationship between the two input geometries. The matrix string can be tested for matching a DE-9IM pattern using ST_RelateMatch.

Variant 3: Like variant 2, but allows specifying a Boundary Node Rule. A boundary node rule allows finer control over whether geometry boundary points are considered to lie in the DE-9IM Interior or Boundary. The boundaryNodeRule code is: 1: OGC/MOD2, 2: Endpoint, 3: MultivalentEndpoint, 4: MonovalentEndpoint.

This function is not in the OGC spec, but is implied. see s2.1.13.2

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

Performed by the GEOS module

Enhanced: 2.0.0 - added support for specifying boundary node rule.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

Examples

Using the boolean-valued function to test spatial relationships.

SELECT ST_Relate('POINT(1 2)', ST_Buffer( 'POINT(1 2)', 2), '0FFFFF212');
st_relate
-----------
t

SELECT ST_Relate(POINT(1 2)', ST_Buffer( 'POINT(1 2)', 2), '*FF*FF212');
st_relate
-----------
t

Testing a custom spatial relationship pattern as a query condition, with && to enable using a spatial index.

-- Find compounds that properly intersect (not just touch) a poly (Interior Intersects)

SELECT c.* , p.name As poly_name
    FROM polys AS p
    INNER JOIN compounds As c
          ON c.geom && p.geom
             AND ST_Relate(p.geom, c.geom,'T********');

Computing the intersection matrix for spatial relationships.

SELECT ST_Relate( 'POINT(1 2)',
                  ST_Buffer( 'POINT(1 2)', 2));
st_relate
-----------
0FFFFF212

SELECT ST_Relate( 'LINESTRING(1 2, 3 4)',
                  'LINESTRING(5 6, 7 8)' );
st_relate
-----------
FF1FF0102

Name

ST_RelateMatch — Tests if a DE-9IM Intersection Matrix matches an Intersection Matrix pattern

Synopsis

boolean ST_RelateMatch(text intersectionMatrix, text intersectionMatrixPattern);

Description

Tests if a Dimensionally Extended 9-Intersection Model (DE-9IM) intersectionMatrix value satisfies an intersectionMatrixPattern. Intersection matrix values can be computed by ST_Relate.

For more information refer to Section 5.1, “Determining Spatial Relationships”.

Performed by the GEOS module

Availability: 2.0.0

Examples

SELECT ST_RelateMatch('101202FFF', 'TTTTTTFFF') ;
-- result --
t

Patterns for common spatial relationships matched against intersection matrix values, for a line in various positions relative to a polygon

SELECT pat.name AS relationship, pat.val AS pattern,
       mat.name AS position, mat.val AS matrix,
       ST_RelateMatch(mat.val, pat.val) AS match
    FROM (VALUES ( 'Equality', 'T1FF1FFF1' ),
                 ( 'Overlaps', 'T*T***T**' ),
                 ( 'Within',   'T*F**F***' ),
                 ( 'Disjoint', 'FF*FF****' )) AS pat(name,val)
    CROSS JOIN
        (VALUES  ('non-intersecting', 'FF1FF0212'),
                 ('overlapping',      '1010F0212'),
                 ('inside',           '1FF0FF212')) AS mat(name,val);

 relationship |  pattern  |     position     |  matrix   | match
--------------+-----------+------------------+-----------+-------
 Equality     | T1FF1FFF1 | non-intersecting | FF1FF0212 | f
 Equality     | T1FF1FFF1 | overlapping      | 1010F0212 | f
 Equality     | T1FF1FFF1 | inside           | 1FF0FF212 | f
 Overlaps     | T*T***T** | non-intersecting | FF1FF0212 | f
 Overlaps     | T*T***T** | overlapping      | 1010F0212 | t
 Overlaps     | T*T***T** | inside           | 1FF0FF212 | f
 Within       | T*F**F*** | non-intersecting | FF1FF0212 | f
 Within       | T*F**F*** | overlapping      | 1010F0212 | f
 Within       | T*F**F*** | inside           | 1FF0FF212 | t
 Disjoint     | FF*FF**** | non-intersecting | FF1FF0212 | t
 Disjoint     | FF*FF**** | overlapping      | 1010F0212 | f
 Disjoint     | FF*FF**** | inside           | 1FF0FF212 | f

Name

ST_Touches — Returns true if two geometries have at least one point in common, but their interiors do not intersect.

Synopsis

boolean ST_Touches(geometry A, geometry B);

Description

Returns TRUE if A and B intersect, but their interiors do not intersect. Equivalently, A and B have at least one point in common, and the common points lie in the intersection of their boundaries. For Point/Point inputs the relationship is always FALSE, since points do not have a boundary.

In mathematical terms, this relationship is expressed as:

This relationship holds if the DE-9IM Intersection Matrix for the two geometries matches one of:

  • FT*******

  • F**T*****

  • F***T****

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid using an index, use _ST_Touches instead.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.28

Examples

The ST_Touches predicate returns TRUE in all the following illustrations.

POLYGON / POLYGON

POLYGON / POLYGON

POLYGON / LINESTRING

LINESTRING / LINESTRING

LINESTRING / LINESTRING

POLYGON / POINT

SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(1 1)'::geometry);
 st_touches
------------
 f
(1 row)

SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(0 2)'::geometry);
 st_touches
------------
 t
(1 row)

Name

ST_Within — Returns true if no points of A lie in the exterior of B, and A and B have at least one interior point in common.

Synopsis

boolean ST_Within(geometry A, geometry B);

Description

Returns TRUE if geometry A is completely inside geometry B. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. It is a given that if ST_Within(A,B) is true and ST_Within(B,A) is true, then the two geometries are considered spatially equal.

A subtlety of this definition is that the boundary of a geometry is not within the geometry. This means that lines and points lying in the boundary of a polygon or line are not within the geometry. For further details see Subtleties of OGC Covers, Contains, Within. (The ST_CoveredBy predicate provides a more inclusive relationship).

ST_Within is the inverse of ST_Contains. So, ST_Within(A,B) = ST_Contains(B,A).

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function _ST_Within.

Performed by the GEOS module

Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.

[Important]

Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION

[Important]

Do not use this function with invalid geometries. You will get unexpected results.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 - a.Relate(b, 'T*F**F***')

This method implements the SQL/MM specification. SQL-MM 3: 5.1.30

Examples

--a circle within a circle
SELECT ST_Within(smallc,smallc) As smallinsmall,
        ST_Within(smallc, bigc) As smallinbig,
        ST_Within(bigc,smallc) As biginsmall,
        ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,
        ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,
        ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion
FROM
(
SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc,
        ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo;
--Result
 smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion
--------------+------------+------------+------------+------------+------------
 t            | t          | f          | t          | t          | t
(1 row)
                

8.11.2. Distance Relationships

ST_3DDWithin — Returns true if two 3D geometries are within a given 3D distance
ST_3DDFullyWithin — Returns true if two 3D geometries are entirely within a given 3D distance
ST_DFullyWithin — Returns true if two geometries are entirely within a given distance
ST_DWithin — Returns true if two geometries are within a given distance
ST_PointInsideCircle — Tests if a point geometry is inside a circle defined by a center and radius.

Name

ST_3DDWithin — Returns true if two 3D geometries are within a given 3D distance

Synopsis

boolean ST_3DDWithin(geometry g1, geometry g2, double precision distance_of_srid);

Description

Returns true if the 3D distance between two geometry values is no larger than distance distance_of_srid. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense the source geometries must be in the same coordinate system (have the same SRID).

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This method implements the SQL/MM specification. SQL-MM ?

Availability: 2.0.0

Examples

-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
-- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
SELECT ST_3DDWithin(
                        ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
                        ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
                        126.8
                ) As within_dist_3d,
ST_DWithin(
                        ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
                        ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
                        126.8
                ) As within_dist_2d;

 within_dist_3d | within_dist_2d
----------------+----------------
 f              | t

Name

ST_3DDFullyWithin — Returns true if two 3D geometries are entirely within a given 3D distance

Synopsis

boolean ST_3DDFullyWithin(geometry g1, geometry g2, double precision distance);

Description

Returns true if the 3D geometries are fully within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Examples

-- This compares the difference between fully within and distance within as well
                -- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully within
                SELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, geom_b, 10) as D3DWithin10,
        ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,
        ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from
                (select ST_GeomFromEWKT('POINT(1 1 2)') as geom_a,
                ST_GeomFromEWKT('LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)') as geom_b) t1;
 d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20
------------------+-------------+------------------+------------------
 f                | t           | t                | f 

Name

ST_DFullyWithin — Returns true if two geometries are entirely within a given distance

Synopsis

boolean ST_DFullyWithin(geometry g1, geometry g2, double precision distance);

Description

Returns true if the geometries are entirely within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

[Note]

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Availability: 1.5.0

Examples

postgis=# SELECT ST_DFullyWithin(geom_a, geom_b, 10) as DFullyWithin10, ST_DWithin(geom_a, geom_b, 10) as DWithin10, ST_DFullyWithin(geom_a, geom_b, 20) as DFullyWithin20 from
                (select ST_GeomFromText('POINT(1 1)') as geom_a,ST_GeomFromText('LINESTRING(1 5, 2 7, 1 9, 14 12)') as geom_b) t1;

-----------------
 DFullyWithin10 | DWithin10 | DFullyWithin20 |
---------------+----------+---------------+
 f             | t        | t             |  

Name

ST_DWithin — Returns true if two geometries are within a given distance

Synopsis

boolean ST_DWithin(geometry g1, geometry g2, double precision distance_of_srid);

boolean ST_DWithin(geography gg1, geography gg2, double precision distance_meters, boolean use_spheroid = true);

Description

Returns true if the geometries are within a given distance

For geometry: The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must be in the same coordinate system (have the same SRID).

For geography: units are in meters and distance measurement defaults to use_spheroid=true. For faster evaluation use use_spheroid=false to measure on the sphere.

[Note]

Use ST_3DDWithin for 3D geometries.

[Note]

This function call includes a bounding box comparison that makes use of any indexes that are available on the geometries.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

Availability: 1.5.0 support for geography was introduced

Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details.

Enhanced: 2.1.0 support for curved geometries was introduced.

Prior to 1.3, ST_Expand was commonly used in conjunction with && and ST_Distance to test for distance, and in pre-1.3.4 this function used that logic. From 1.3.4, ST_DWithin uses a faster short-circuit distance function.

Examples

-- Find the nearest hospital to each school
-- that is within 3000 units of the school.
--  We do an ST_DWithin search to utilize indexes to limit our search list
--  that the non-indexable ST_Distance needs to process
-- If the units of the spatial reference is meters then units would be meters
SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.geom, h.hospital_name
        FROM schools s
                LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.geom, 3000)
        ORDER BY s.gid, ST_Distance(s.geom, h.geom);

-- The schools with no close hospitals
-- Find all schools with no hospital within 3000 units
-- away from the school.  Units is in units of spatial ref (e.g. meters, feet, degrees)
SELECT s.gid, s.school_name
        FROM schools s
                LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
        WHERE h.gid IS NULL;

-- Find broadcasting towers that receiver with limited range can receive.
-- Data is geometry in Spherical Mercator (SRID=3857), ranges are approximate.

-- Create geometry index that will check proximity limit of user to tower
CREATE INDEX ON broadcasting_towers using gist (geom);

-- Create geometry index that will check proximity limit of tower to user
CREATE INDEX ON broadcasting_towers using gist (ST_Expand(geom, sending_range));

-- Query towers that 4-kilometer receiver in Minsk Hackerspace can get
-- Note: two conditions, because shorter LEAST(b.sending_range, 4000) will not use index.
SELECT b.tower_id, b.geom
  FROM broadcasting_towers b
  WHERE ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', 4000)
          AND ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', b.sending_range);

                          

Name

ST_PointInsideCircle — Tests if a point geometry is inside a circle defined by a center and radius.

Synopsis

boolean ST_PointInsideCircle(geometry a_point, float center_x, float center_y, float radius);

Description

Returns true if the geometry is a point and is inside the circle with center center_x,center_y and radius radius.

[Warning]

Does not use spatial indexes. Use ST_DWithin instead.

Availability: 1.2

Changed: 2.2.0 In prior versions this was called ST_Point_Inside_Circle

Examples

SELECT ST_PointInsideCircle(ST_Point(1,2), 0.5, 2, 3);
 st_pointinsidecircle
------------------------
 t

See Also

ST_DWithin

8.12. Measurement Functions

Abstract

These functions compute measurements of distance, area and angles. There are also functions to compute geometry values determined by measurements.

ST_Area — Returns the area of a polygonal geometry.
ST_Azimuth — Returns the north-based azimuth as the angle in radians measured clockwise from the vertical on pointA to pointB.
ST_Area — Returns the angle between 3 points, or between 2 vectors (4 points or 2 lines).
ST_ClosestPoint — Returns the 2D point on g1 that is closest to g2. This is the first point of the shortest line.
ST_3DClosestPoint — Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.
ST_Distance — Returns the distance between two geometry or geography values.
ST_3DDistance — Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
ST_DistanceSphere — Returns minimum distance in meters between two lon/lat geometries using a spherical earth model.
ST_DistanceSpheroid — Returns the minimum distance between two lon/lat geometries using a spheroidal earth model.
ST_Distance — Returns the Fréchet distance between two geometries.
ST_HausdorffDistance — Returns the Hausdorff distance between two geometries.
ST_Length — Returns the 2D length of a linear geometry.
ST_Length2D — Returns the 2D length of a linear geometry. Alias for ST_Length
ST_3DLength