Polygon construction is one of the most important and difficult parts in the establishments of topological relationships of geographic data

and its automation

speed and complexity hedge the development of related modules of GISs and the establishments of geographic data bases. A speedy polygon auto-construction algorithm based on azimuth calculation is put forward in this paper

which constructs polygons and deals with the problems of“islands”and“enclaves”successfully. The algorithm's structure is concise

easily understandable and conveniently programmable.