Polygon A planar Surface defined by 1 exterior boundary and 0 or more interior boundaries. Each interior boundary defines a hole in the Polygon. Polygons are topologically closed. Polygons are a subclass of Surface that is planar. A Surface is a 2-dimensonal geometric object. Represented in 2D coordinates by FeatureGeometry. 2D OGC Simple Features Simple Features OGC document (pdf): http://portal.opengeospatial.org/files/?artifact_id=25355 See also this more accessible description of Simple Features Well-Known Text terms: http://en.wikipedia.org/wiki/Well-known_text ODM2 SamplingFeatureGeotype Controlled Vocabulary ODM2 Working Group A vocabulary for describing the geospatial feature type associated with a SamplingFeature. For example, Site SamplingFeatures are represented as points. In ODM2, each SamplingFeature may have only one geospatial type, but a geospatial types may range from simple points to a complex polygons or even three dimensional volumes.