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 - MultiPointmay contain only- Pointelements)
- Dimension 
- Constraints on the degree of spatial overlap between elements