Digital maps are used widely these days, and they are prone to be illegally copied and distributed. However, there have been few copyright protection techniques for digital maps. In this thesis, data hiding methods for digital map are proposed.
We present a data hiding algorithm for vector digital maps. The polygonal line is represented by the wavelet descriptor. An additive watermarking scheme is used to embed the watermark by slightly modifying the wavelet descriptor, and that causes invisible distortions to the coordinates of the vertices. The invariant properties of the wavelet descriptor ensure that the presented algorithm is resilient against both global and local geometrical distortions. Using vector graphic images from contour maps, we demonstrate that the presented algorithm outperforms the conventional algorithm based on the Fourier descriptor.
We also propose a data hiding method for raster digital maps. The proposed algorithm parameterizes a curve using the B-spline model and treats B-spline control points as a point set, and creates a 2D mesh by using Delaunay triangulation with the point set. The mesh spectral coefficients are computed by using the mesh spectral analysis. Watermark messages are embedded in this mesh spectral domain, and the coefficients are inverse transformed to the coordinates of the control points. By using B-spline model, the watermarked curve is reconstructed with the control points. Experimental results show that the proposed scheme is robust against printing-scanning attack as well as global geometric distortion.
We present another data hiding method for raster digital maps. In order to fingerprint digital maps, this paper addresses an efficient data hiding technique for curves. We choose the embedding domain based on the curvature of sample points and alter the coordinates of selected sample points for watermark embedding. The watermarked curve is reconstructed using Bezier curve segments. The use of Bezier mod...