An Efficient and Topologically Correct Map Generalization Heuristic

We present TopoVW, an efficient heuristic for map simplification that deals with a variation of the generalization problem where the idea is to simplify the polylines of a map without changing the topological relationships between these polylines or between the lines and control points. This process is important for maintaining clarity of cartographic data, avoiding situations such as high density of map features, inappropriate intersections. In practice, high density of features may be represented by cities condensed into a small space on the map, inappropriate intersections may produce intersections between roads, rivers, and buildings. TopoVW is a strategy based on the Visvalingam-Whyatt algorithm to create simplified geometries with shapes similar to the original map, preserving topological consistency between features in the output. It uses a point ranking strategy, in which line points are ranked by their effective area, a metric that determines the impact a point will cause to the geometry if removed from the line. Points with inferior effective area are eliminated from the original line. The method was able to process a map with 4 million line points and 10 million control points in less than 2 minutes on a Intel Core 2 Duo processor.