Polygon Overlay Analysis Algorithm Based on Monotone Chain and STR Tree in the Simple Feature Model

An improved overlay analysis algorithm based on monotone chain and STR (Sort-Tile-Recursive) tree index is introduced. The algorithm can save the time for vertex listing and intersection point computation, also the memory space. Making full use of the function of overlay analysis for simple features, as many as possible nodes of the polygon can be filled in the STR tree index structure. The algorithm reduces the access times when querying the polygons in the spatial database. The algorithm splits the edges in the polygon by the monotone chain algorithm to compute the intersect point firstly. Secondly, the concept of plane graph is used in this algorithm. The algorithm organizes the result polygons by computing the topology location between the plane graph components of the two polygons. It has been reduced the computing intersect point time and emphasizes on the solution of the problem of the entry point or exit-point successive and the alternative searching of the intersected polygon. Performance tests show the algorithm is more efficient and quicker than the algorithm based on the topological model and the other algorithms.