Flexibility of <Polygon> as a Class
<Polygons> may be colored, texture-mapped, or both.
<Polygons> may have any number of vertices, as long as they have at least 3.
See sheet 5 of the DRM diagram for further specifics.
<Vertices>, in turn, support <Locations> in any spatial reference frame supported by the DRM. They may also provide texture-coordinate information, or have their own <Colors>, or both.