A property that has a point as its value domain can either be an appropriate geometry element encapsulated in an
element of this type or an XLink reference to a remote geometry element (where remote includes geometry elements located
elsewhere in the same document).
A two-dimensional coordinate system in which position is specified by the distance from the origin and the angle between the line from the origin to a point and a reference direction.
A 2D coordinate reference system used to approximate the shape of the earth on a planar surface, but in such a way that the distortion that is inherent to the approximation is carefully controlled and known.