Copyright protection of vector map using digital watermarking method based on discrete Fourier transform

In this paper, a new digital watermarking method for vector maps is proposed, where the watermark can be embedded in a set of polylines by using the discrete Fourier transform (DFT). The robustness against external attacks and visual degradation caused by embedding were evaluated, and the effectiveness of the watermarking was confirmed. Our watermarking method is especially robust against vertex reordering attacks and noise imposition on the vertex coordinates.