Performing boundary shape matching in spatial data

Edwin M. Knorr, Raymond T. Ng, David L. Shilvock Department of Computer Science University of British Columbia Vancouver, B.C., V6T 1Z4, Canada fknorr,[email protected] Abstract This paper describes a new approach to knowledge discovery among spatial objects|namely that of partial boundary shape matching. Our focus is on mining spatial data, whereby many objects called features (represented as polygons) are compared with one or more point sets called clusters. The research described has practical application in such domains as Geographic Information Systems, in which a cluster of points (possibly created by an SQL query) is compared to many natural or manmade features to detect partial or total matches of the facing boundaries of the cluster and feature. We begin by using an alpha-shape to characterize the shape of an arbitrary cluster of points, thus producing a set of edges denoting the cluster's boundary. We then provide an approach for detecting a boundary shape match between the facing curves of the cluster and feature, and show how to quantify the value of the match. Optimizations and experimental results are also provided. Finally, we describe several orientation strategies yielding signi cant performance enhancements.