GeometryCollection is a geometry that is
a collection of zero or more geometries of any class.
All the elements in a geometry collection
must be in the same spatial reference system (that is, in the
same coordinate system). There are no other constraints on the
elements of a geometry collection, although
the subclasses of
described in the following sections may restrict membership.
Restrictions may be based on:
Element type (for example, a
MultiPointmay contain only
Constraints on the degree of spatial overlap between elements