Section B.1. What Is a Polygon?

B.1. What Is a Polygon?

Polygons are defined by an ordered series of latitude/longitude points (vertices) with an implied connection between consecutive vertices and between the last and first vertex. A polygon data source can contain one or more polygons, and a single polygon data source can contain up to 500 vertices. Each polygon consists of a single external ring and may include multiple internal rings. When you create a polygon, you must first define the external ring. Figure B-1 shows the external ring of a polygon with 6 vertices and the implied edges drawn between each

In addition to the external ring, a polygon can contain one or more internal rings. Like the external ring, internal rings are defined by an ordered list of vertices, and no two implied edges may intersect. Therefore, each internal ring must be entirely contained within the external ring. In addition, you cannot create an internal ring within an existing internal ring. Figure B-2 shows a polygon with one external ring with two internal rings.

Figure B-1. Simple polygon with edges and vertices

Figure B-2. Complex polygon with inner and outer rings