Alias

Centroid

Description

Returns the centroid (geometric center) of a geometry, which may lie outside the geometry.

The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid)

	The centroid will have the same SRID as the incoming geometry.

Coordinate Dimensions

2D	3D	M
	-	-

Spatial Standards Support

Examples

SELECT ST_AsEWKT(ST_Centroid(ST_GeomFromText('MULTIPOINT (0 0, 8 0, 5 10, 10 10, 15 20, 10 20)',25830)));
--Result
SRID=25830;POINT (8 10)

SELECT ST_AsEWKT(ST_Centroid(ST_GeomFromText('POLYGON((0 0 2, 0 10 4, 10 10 5, 10 0 5, 0 0 2))')));
--Result
POINT (5 5)

MULTIPOINT CENTROID	LINESTRING CENTROID
POLYGON CENTROID	GEOMETRY COLLECTION CENTROID

This example extracts the Centroid of a set of Parcels. 
The parcels are stored in the parcels table created with a CREATE TABLE statement. 
The INSERT INTO statements that follow insert each one of the parcels geometries.

CREATE TABLE "parcels"(id serial PRIMARY KEY);
SELECT AddGeometryColumn ('parcels','geom',-1,'POLYGON',2);
INSERT INTO "parcels"("geom") SELECT (ST_GeomFromText('POLYGON((6 14, 7.5 15, 10 11, 8 10, 6 14))'));
INSERT INTO "parcels"("geom") SELECT (ST_GeomFromText('POLYGON((7 12, 4 10, 3 12, 6 14, 7 12))'));
INSERT INTO "parcels"("geom") SELECT (ST_GeomFromText('POLYGON((5 8, 4 10, 7 12, 8 10, 5 8))'));

SELECT ST_AsText(ST_Centroid("geom")) from (SELECT "geom" from "parcels") as foo;
SELECT DropGeometryTable('parcels');

--Result
                     st_astext
-----------------------------------------------------
 MULTIPOINT ((7.923423423423424 12.432432432432432))
 MULTIPOINT ((5 12))
 MULTIPOINT ((6 10))

Parcels

ST_Multicentroid

Related functions

ST_MultiCentroid, ST_PointOnSurface