As of PostGIS 3.0, the PostGIS raster support is no longer part of the postgis extension, but instead spun off into a new PostGIS extension called postgis_raster.

The two main reasons for this break were:

• Raster functionality in PostGIS is fat with over 150 functions and several types. Wading through these extra …

As of PostGIS 2.3, the postgis extension was changed to no longer allow relocation. All function calls within the extension are now schema qualified.

While this change fixed some issues with database restore, it created the issue of if you installed PostGIS in a schema other than the one you wanted to it is not …

The error 'postgis.backend' is already set comes up every so often in PostGIS mailing list. The issue arises often during or after an upgrade. I'll go over causes for this I am aware of and how to fix.

The question goes something like this

This raster question comes up quite a bit on PostGIS mailing lists and stack overflow and the best answer often involves the often forgotten ST_Reclass function that has existed since PostGIS 2.0. People often resort to the much slower though more flexible ST_MapAlgebra or dumping out their rasters as Pixel valued …

PostGIS 2.2.0 came out this month, and the SFCGAL extension that offers advanced 3D and volumetric support, in addition to some extended 2D functions like ST_ApproximateMedialAxis became a standard PostgreSQL extension and seems to be a fairly popular extension.

I've seen several reports on GIS Stack Exchange of people …

I've been asked this question in some shape or form at least 3 times, mostly from people puzzled why they get this error. The last iteration went something like this:

I can't use ST_AsPNG when doing something like

1SELECT ST_AsPNG(rast)
2    FROM  sometable;

Gives error: Warning: pg_query(): Query failed: ERROR: …

PostGIS raster has so so many functions and probably at least 10 ways of doing something some much much slower than others. Suppose you have a raster, or you have a raster area of interest -- say elevation raster for example, and you want to know the distinct pixel values in the area. The temptation is to reach for …

Doing an ST_Intersection is much slower than relation checks such as ST_Intersects , ST_CoveredBy, and , ST_Within . In many situations you know the intersection of 2 geometries without actually computing an intersection. In these cases, you can skip the costly ST_Intersection call. Cases like this:

1. geometry a is …

Every one or two months, someone asks on the PostGIS users list usually somewhat panicked, My geometry is missing when I look in pgAdmin III

This is documented in the PostGIS Frequently Asked questions section of the manual I tried to use PgAdmin to view my geometry column and it is blank, what gives?

Since this …

People often get confused between the ST_Transform and ST_SetSRID functions.

1. ST_SetSRID doesn't change the coordinates but adds meta data to state what spatial reference system the coordinate actually are. If you stamped your WGS 84 long lat data as a meter based projection. Guess what? Its still long lat. A spade …