ST_Centroid returns a point that represents a centroid of a geometry as follows:
For
POINTgeometries, it returns the point whose coordinates are the average of the coordinates of the points in the geometry.For
LINESTRINGgeometries, it returns the point whose coordinates are the weighted average of the midpoints of the segments of the geometry, where the weights are the lengths of the segments of the geometry.For
POLYGONgeometries, it returns the point whose coordinates are the weighted average of the centroids of a triangulation of the areal geometry where the weights are the areas of the triangles in the triangulation.For geometry collections, it returns the weighted average of the centroids of the geometries of maximum topological dimension in the geometry collection.
Syntax
ST_Centroid(geom)
Arguments
- geom
-
A value of data type
GEOMETRYor an expression that evaluates to aGEOMETRYtype.
Return type
GEOMETRY
If geom is null, then null is returned.
If geom is empty, then null is returned.
Examples
The following SQL returns central point of an input linestring.
SELECT ST_AsEWKT(ST_Centroid(ST_GeomFromText('LINESTRING(110 40, 2 3, -10 80, -7 9, -22 -33)', 4326)))
st_asewkt
----------------------------------------------------
SRID=4326;POINT(15.6965103455214 27.0206782881905)
