The "_SurfacePatch" element is the abstract head of the substituition group for all surface pach elements describing a continuous portion of a surface.
<element name="_SurfacePatch" type="gml:AbstractSurfacePatchType" abstract="true"><annotation><documentation>The "_SurfacePatch" element is the abstract head of the substituition group for all surface pach elements describing a continuous portion of a surface.</documentation></annotation></element>