Embedding watermark in a digital vector map could generally degrade the quality of the map data.However

invertible watermarking(or lossless data hiding) is more appropriaue to vector maps for its ability to recover the original cover data.A lossless data hiding algorithm for digital vector maps based on difference expansion is proposed in this paper.According to the vector map's special requirement to data precision

an embedding condition is firstly presented.The watermark can be embedded by modifying the coordinate differences between the adjacent vertices and the original map can be recovered bit-by-bit after the watermark has been extracted.Two kinds of original maps are used in the experiments and the results indicate that higher payload and lower distortions could be achieved in the maps with higher correlated coordinates.The potential usages of the proposed scheme would include the map data authentication

meta data format compatibility

and secret communication based on vector maps.