A GeomCollection is a geometry that is a collection of zero or more geometries of any class.
GeomCollection and GeometryCollection are synonymous, with GeomCollection the preferred type name.
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 GeomCollection described in the following sections may restrict membership. Restrictions may be based on:
Element type (for example, a MultiPoint may contain only Point elements)
Dimension
Constraints on the degree of spatial overlap between elements