A new watermarking method for vector map data: a study on information capacity of the carrier image

Abstract

The paper presents a study of the watermarking method for vector map data based on the cyclic shift of the vertex list of polygonal objects. We propose a method modification to provide an accurate authentication procedure, as well as to enhance the method robustness against the map contents alteration. The main idea of the improved method is to use a noise-like image as a secondary container for a watermark represented in the form of a bit vector. An algorithm for the construction of a carrier image on the basis of the watermark sequence, as well as an algorithm for extraction of such a sequence, are given. An experimental study on the information capacity of the carrier image and its robustness against distortions simulating the embedding into real cartographic data, such as quantization and noise addition, has been carried out.