Comparative Study of Compact Descriptors for Vector Map Protection
The paper is devoted to the study of compact descriptors of a vector map to be used as a zero watermark in the problems of cartographic data protection, namely, copyright protection and protection against unauthorized changes. The applicability of descriptors for these problems is determined by the characteristics of the resistance of their values to map transformations (adding, deleting vertices and individual objects, rotating the map, changing the order of the vertices of map objects, etc.). All descriptors are based on the use of the Ramer-Douglas-Pecker algorithm to extract a significant part of the polygons that determine the shape of the object. In our experimental studies, a map of urban development was used, which was divided into equal sections. Compact descriptors were calculated for each of them. Next, the map distortion procedure was performed, after which the stability of the descriptor values was checked. The conducted studies revealed the best descriptor for solving the copyright protection problem, as well as several combinations of other descriptors to identify certain distortions of the vector map. In addition, a modification of the Ramer-DouglasPecker algorithm, which is more efficient than the basic algorithm, is proposed.