Vector map is the most important spatial map widely used in GIS, navigation, and network services. Watermarking technology must be developed for vector map to address the copyright issue. In this paper, Vector map Watermarking under Topological Conformance (VWTC for short) for vector maps is proposed. After subdividing vector map into blocks, watermark information is embedded into the coordinates of vertices when ensuring comformance of all topological relationships. Unlike other current algorithms, VWTC compares the watermarked map being examined with the original watermarked map instead of the primitive map. Another specific feature of VWTC is that it uses mean-value comparison in vertices matching and the comparison is guided by the attributes-priority rule to reduce possible matching errors and to increase efficiency at the same time. A series of anti-attacks experiments such as random noise, vertices insertion, layers deletion, and linea transformation are conducted. The experiments results show that VWTC is more robust and achieves higher usability.

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Abstract.A distributed map data parallel dissemination system, which can be used to distribute spatial map data to remote users through different networks, is presented. The paper first defines spatial map data, associated metadata and network resource nodes with graphic formalization definition. Then, the relations between map data and network resources are established. Based on formalized definition to the whole system, a map data dissemination framework and a series of essential distributed CORBA services, conditions input methods based on three querying conditions are presented. We also explore network map copyright validating in dissemination course, and present an improved adaptive watermarking algorithm for vector digital maps whose data is the most difficult and necessary to watermark. Different from other methods, we compare the watermarked map with the original watermarked map, not with the primitive map, before extraction. The results show that compared with Direct Copy, our dissemination system can delivery spatial map data effectively. The transfer performance of CORBA services mode is almost equal to Direct Copy. The system can approach the biggest transfer rate more quickly but dependents on data amount weakly. And, the improved watermarking algorithm has better robustness.