Polygon Geometry

Polygon geometry is a GeoJSON geometry type that represents a closed shape on a map by connecting a series of coordinate points. In the context of Apple Maps routing integration, polygons define the exact geographic boundaries where your app can provide directions. Each polygon consists of at least one linear ring - an ordered array of longitude-latitude pairs where the first and last point are identical, closing the shape.

Structure of a GeoJSON Polygon

A polygon’s outer boundary is called the exterior ring. You can also include interior rings that act as holes, carving out areas within the polygon where your service does not operate. Coordinates use the WGS 84 reference system and are written as [longitude, latitude] pairs. A simple rectangular coverage area needs five coordinate points: four corners plus a repeat of the first point to close the ring.

Using Polygons in Routing Coverage Files

When building your routing app coverage file, you place polygon geometry inside GeoJSON Feature objects. For apps that serve multiple disconnected regions, you can use a MultiPolygon geometry type that groups several polygons into a single feature. Keeping polygons as simple as possible reduces file size and processing time. Avoid unnecessary detail in coastlines or borders unless your service boundary truly follows those contours.