Polygons
The Geospatial Toolkit supports polygons that are formed by a set of non-intersecting exterior and interior rings. Each ring is oriented as per the left-hand rule. Consider an imaginary user walking along the ring, the area to the left of this user is inside the polygon, whereas the area to the right of the user is outside the polygon. The polygon and orientedPolygon functions in the com.ibm.streams.geospatial.ext namespace are provided as a convenience to assist in constructing polygons in the aforementioned format.
The polygons can span large areas such as the Pacific Ocean, Polar cap, Southern hemisphere, and the United States. A closed manifold such as an ellipsoid or spheroid requires an oriented ring to uniquely define a polygon. In contrast, on an infinite plane, a non self-intersecting ring divides the plane into two regions: one with finite and the other with infinite area. The planar polygon is simply chosen to be the one with finite area. However, on the ellipsoid, the non self-intersecting ring divides the surface of the ellisoid into two regions, both with finite areas. The orientation of the ring enforces the choice of the area thus uniquely defining a polygon.
The namespaces com.ibm.streams.geospatial.twodimension.geometry and com.ibm.streams.geospatial.conversions have been deprecated, as have all types and functions defined therein.