ST_Centroid

Calculates the geometric center—the centroid—of a spatial object. If points or linestrings or both are present in a geometry with polygons, only the polygons contribute to the calculation of the centroid. Similarly, if points are present with linestrings, the points do not contribute to the calculation of the centroid.

To calculate the centroid of a GEOGRAPHY object, see the examples for STV_Geometry and STV_Geography.

Behavior type

Syntax

ST_Centroid( g )

Arguments

g

Spatial object for which you want to calculate the centroid, type GEOMETRY

Returns

GEOMETRY (POINT only)

Supported data types

Examples

The following examples show how to use ST_Centroid.

Calculate the centroid for a polygon:

=> SELECT ST_AsText(ST_Centroid(ST_GeomFromText('POLYGON((-1 -1,2 2,-1 2,
   -1 -1))')));
  ST_AsText
------------
 POINT (-0 1)
(1 row)

Calculate the centroid for a multipolygon:

=> SELECT ST_AsText(ST_Centroid(ST_GeomFromText('MULTIPOLYGON(((1 0,2 1,2 0,
   1 0)),((-1 -1,2 2,-1 2,-1 -1)))')));
               ST_AsText
--------------------------------------
 POINT (0.166666666667 0.933333333333)
(1 row)

This figure shows the centroid for the multipolygon.