This paper describes a computer program (SIGAP) that analyzes digitized LSI mask data for valid and invalid Silicon Gate transistor geometries. The program's function, as well as the topological mapping technique used, are described. The SIGAP techniques can be adopted to a variety of artwork data preparation tasks, such as elimination of redundancy, overlap creation, area shrink/expand, the decomposition of polygons to equivalent rectangles or vice versa and performing Boolean operations between regions on different masks. The program was implemented in assembly language on a mini-computer using structured programming methods. It efficiently handles data files which are much larger than available core memory.