Abstract: This application is directed to matching edges of polygons representing neighboring regions in a map user application. A computer system obtains a first polygon and a second polygon, and the second polygon is connected to the first polygon via polygon edges that are at least partially mismatched. Automatically and without user intervention, the computer system combines the first polygon and the second polygon to form a joined polygon defined by an outline of the first polygon and the second polygon. A region defined by the second polygon is subtracted from a region defined by the joined polygon to form a new region. The computer system defines an updated first polygon as an outline of the new region and renders, on a screen, the updated first polygon and the second polygon with matching edges.