Function Area returns the area of a polygon, or the combined area of a MultiPolygon, assuming that none of the polygons in the MultiPolygon overlap and that nested polygons have alternating winding directions.

Calculate the centroid of a polygon, from wikipedia: http://en.wikipedia.org/wiki/Centroid#Centroid_of_polygon.

Clone returns a duplicate of a polygon.

Distance returns the distance between the closest parts of two geometries.

Change the winding direction of the outer and inner rings so the outer ring is counter-clockwise and nesting rings alternate directions.

Function Length returns the length of a LineString, or the combined length of a MultiLineString.

Equals returns true if both p1 and p2 describe the same point within a tolerance limit.

Function PointOnSurface returns a point guaranteed to lie on the surface of the shape.

Within checks whether inner is within outer.

Op describes an operation which can be performed on two polygons.