Name
ST_Segmentize — Returns a modified geometry/geography having no segment longer than a given distance.
Synopsis
geometry ST_Segmentize(geometry geom, float max_segment_length);
geography ST_Segmentize(geography geog, float max_segment_length);
Beschreibung
Returns a modified geometry/geography having no segment longer than max_segment_length. Length is computed in 2D. Segments are always split into equal-length subsegments.
For geometry, the maximum length is in the units of the spatial reference system.
For geography, the maximum length is in meters. Distances are computed on the sphere. Added vertices are created along the spherical great-circle arcs defined by segment endpoints.
![[Note]](../images/note.png) | |
This only shortens long segments. It does not lengthen segments shorter than the maximum length. |
![[Warning]](../images/warning.png) | |
For inputs containing long segments, specifying a relatively short |
Verfügbarkeit: 1.2.2
Enhanced: 3.0.0 Segmentize geometry now produces equal-length subsegments
Enhanced: 2.3.0 Segmentize geography now produces equal-length subsegments
Erweiterung: mit 2.1.0 wurde die Unterstützung des geographischen Datentyps eingeführt.
Changed: 2.1.0 As a result of the introduction of geography support, the usage ST_Segmentize('LINESTRING(1 2, 3 4)', 0.5) causes an ambiguous function error. The input needs to be properly typed as a geometry or geography. Use ST_GeomFromText, ST_GeogFromText or a cast to the required type (e.g. ST_Segmentize('LINESTRING(1 2, 3 4)'::geometry, 0.5) )
Beispiele
Segmentizing a line. Long segments are split evenly, and short segments are not split.
SELECT ST_AsText(ST_Segmentize(
'MULTILINESTRING((0 0, 0 1, 0 9),(1 10, 1 18))'::geometry,
5 ) );
---------------------------------------------------
MULTILINESTRING((0 0,0 1,0 5,0 9),(1 10,1 14,1 18))
Segmentizing a polygon:
SELECT ST_AsText(
ST_Segmentize(('POLYGON((0 0, 0 8, 30 0, 0 0))'::geometry), 10));
-------------------------------------------------------
POLYGON((0 0,0 8,7.5 6,15 4,22.5 2,30 0,20 0,10 0,0 0))
Segmentizing a geographic line, using a maximum segment length of 2000 kilometers. Vertices are added along the great-circle arc connecting the endpoints.
SELECT ST_AsText(
ST_Segmentize(('LINESTRING (0 0, 60 60)'::geography), 2000000));
-------------------------------------------------------------
LINESTRING(0 0,4.252632294621186 8.43596525986862,8.69579947419404 16.824093489701564,13.550465473227048 25.107950473646188,19.1066053508691 33.21091076089908,25.779290201459894 41.01711439406505,34.188839517966954 48.337222885886,45.238153936612264 54.84733442373889,60 60)
A geographic line segmentized along a great circle arc