Polygons
The Geospatial Toolkit functions use polygons that are formed by non-self-intersecting exterior and interior rings. A polygon can encompass an area of any size, including large areas such as the Pacific Ocean, the Polar Ice Cap, the Southern Hemisphere, and the United States.
On an infinite plane, a non-self-intersecting ring divides the plane into two regions: one with finite area and another with an infinite area. The planar polygon is the region with finite area. However, on a closed manifold such as an ellipsoid or spheroid, a non self-intersecting ring divides the surface into two regions, both of which have finite areas. The orientation of the ring determines which of the two regions is contained by the polygon.
Each ring is oriented according to the left-hand rule. Consider an imaginary person walking along the ring: the area to the left of this person is inside the polygon, whereas the area to the right of this person is outside the polygon. The polygon and orientedPolygon functions, which are in the com.ibm.streams.geospatial.ext namespace, can assist you in constructing polygons that follow this format.