ST_Centroid — Returns the geometric center of a geometry.

`geometry `

geometry
**ST_Centroid**(`g1``)`

;

Computes the geometric center of a geometry, or equivalently,
the center of mass of the geometry as a `POINT`

. For
[`MULTI`

]`POINT`

s, this is computed
as the arithmetric mean of the input coordinates. For
[`MULTI`

]`LINESTRING`

s, this is
computed as the weighted length of each line segment. For
[`MULTI`

]`POLYGON`

s, "weight" is
thought in terms of area. If an empty geometry is supplied, an empty
`GEOMETRYCOLLECTION`

is returned. If
`NULL`

is supplied, `NULL`

is
returned.

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).

Computation will be more accurate if performed by the GEOS module (enabled at compile time). |

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.1.4, 9.5.5

In each of the following illustrations, the blue dot represents the centroid of the source geometry.

SELECT ST_AsText(ST_Centroid('MULTIPOINT ( -1 0, -1 2, -1 3, -1 4, -1 7, 0 1, 0 3, 1 1, 2 0, 6 0, 7 8, 9 8, 10 6 )')); st_astext ------------------------------------------ POINT(2.30769230769231 3.30769230769231) (1 row)