Spatial Map Data Share and Parallel Dissemination System Based on Distributed Network Services and Digital Watermark

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.