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Returns the spherical centroid of a geography as a Geography point, computed on the sphere using S2:
  • Polygon / MultiPolygon — area-weighted centroid via S2Polygon.getCentroid().
  • LineString / MultiLineString — length-weighted centroid via S2Polyline.getCentroid().
  • Point / MultiPoint — mean of the unit vectors.
  • GeographyCollection — recursive weighted sum across the children.
The result is the unit-length centroid on the sphere. Unlike a planar (lon/lat) centroid, it is correct for antimeridian-crossing and high-latitude geographies. As with JTS for non-convex shapes, the centroid may lie outside the input geometry. Returns NULL when the centroid is undefined (empty geometry, or antipodal points whose unit vectors cancel).

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Signatures

ST_Centroid (A: Geography)

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Parameters

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A
Geography
required
The geography whose spherical centroid is returned.

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Return type

The centroid as a Geography point, or NULL when undefined.

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Example

SELECT ST_AsEWKT(ST_Centroid(ST_GeogFromWKT('POLYGON ((0 0, 2 0, 2 2, 0 2, 0 0))')));

POINT (1 1)
For an antimeridian-crossing polygon, the spherical centroid stays on the antimeridian instead of jumping to the opposite side of the planet, which a planar centroid would do: 
SELECT ST_AsEWKT(ST_Centroid(ST_GeogFromWKT('POLYGON ((170 -1, -170 -1, -170 1, 170 1, 170 -1))')));
-- result: POINT near (180, 0) (or (-180, 0)), NOT (0, 0)