A Shape-Preserving and Robust Watermarking Algorithm for Vector Maps

Most of the existing vector maps watermarking algorithms exploit spatial precision to measure the fidelity of the watermarked data. In fact, spatial precision fails to measure the shape distortion of the watermarked objects. In this paper, a shape-preserving and robust watermarking algorithm is proposed. We identify each polygon using highest significant bit of coordinates of its feature center. We compute the mean feature distance for each polygon and a sequence of mean feature distance is derived and chosen as cover data. We embed watermark using quantization modulation method and scale part of polygons to derive the watermarked data. Experiment results show that the method has good performance to resist attacks such as simplification, additive noise and cropping.