保持拓扑关系与几何特征的矢量地图水印纠正方法研究

Vector map data is an indispensable strategic resource in the national economy, national defense construction and social development. And it has accurate and detailed geographical information, high cost, outstanding economic and military interests. However, it is easy to be duplicated, tampered or illegally transmitted. As a result, it will seriously damage the interests of the owner. In recent years, digital watermarking which has been an effective copyright protection method was frequently used to embed watermark into vector map and detect watermark. But owing to the complex data structures and abstract spatial representations of vector map data, the watermarking process may result in a change of the topology and geometric characteristics, and may reduce the availability of watermarked vector map..To solve this problem, this research project present a watermarking framework for vector map that employs conventional watermarking techniques but still provides the guarantee that the topology and geometric characteristics of vector map data is preserved. We will firstly create the constrained triangulations of our vector map, compute the minimum inscribed circle radius of each vertex adjacent triangles in the constrained triangulations, and get the maximum perturbation regions (MPR) of every vertex. Then we will employ conventional watermarking algorithm for vector map and embed the watermark into the vector map. In addition, we will subsequently detect the problems of topology changes and geometric distortion, and employ the adjustment method of the same vertex topology association to correct error vertices into MPR or without topology changes and geometric distortion, which will improve the availability of watermarked vector map. According to the above ideas, we will perform the experiment using the residential data and road networks data of test area. Finally, we will verify the reliability and validity of the proposed watermarking scheme using the watermark detecting and quality evaluating methods..Overall, the proposed corrective watermarking schema remedies the defects of the watermarking technology of vector map data in keeping geometric features and topology of geographic features to some extent, and our research project may contribute to the application of copyright for vector map data and advance the development of geographic information science.

本项目以矢量地图版权保护的需求为出发点，针对目前矢量地图水印技术忽视地图本质特征研究、对含水印矢量地图可用性分析不够充分、关于如何保持地图拓扑关系与几何特征的水印纠正方法研究相对较少等问题，深入探讨矢量地图水印技术对地图可用性及质量的影响，在满足数字水印鲁棒性要求的同时，构建保持拓扑关系与几何特征的矢量地图水印纠正框架，研究并实现基于拓扑和方向约束的矢量地图水印错误的多方位检查技术，提出结合最大扰动区域和同名点拓扑关联坐标调整的矢量地图水印纠正方法，建立矢量地图水印嵌入和纠正结果的综合评价体系，保证矢量地图嵌入水印前后的要素拓扑关系一致性与几何特征相似性，增强含水印矢量地图的可用性，为现有矢量地图水印技术提供一套自我质量控制的检测方案，从而促进数字水印技术在数字地图版权保护和应用中的不断优化与推广，并最终带动地理信息产业的健康发展。

数字水印是矢量地图版权保护的重要技术方法，但水印嵌入难免会造成矢量地图坐标点扰动，从而降低数据质量及可用性。本项目以“水印嵌入后数据质量检查——矢量地图要素可用性条件约束——含水印矢量地图数据纠正——新型无损水印方案设计”为主线，从理论和技术两个层面，系统研究了保持数据可用性的矢量地图数字水印方法。以不同比例尺、不同类型、不同复杂度的矢量地图为实验数据，复现不同水印方法进行水印嵌入，挖掘并提取不同类型的特征信息，以此为基础展开相关研究，主要研究成果包括：（1）从拓扑关系一致性与几何形态相似性等方面展开含水印矢量地图的质量与可用性评估，采用数学方法、地图学及测量学等方法对质检要素进行定量描述与约束条件设定，既可以查找出违反约束条件的坐标点，又可以从矢量地图本质特征角度评估数据的可用性；（2）基于坐标平差的思路对不满足约束条件的坐标点进行调整，最终结果使所有坐标点满足约束条件，以此提升含水印矢量地图的可用性；通过水印提取实验，确保水印功能不被调整算法所破坏；通过地图参数变更统计，确保纠正算法对地图质量影响较小；（3）提出了多种空间特征提取方法与坐标值内蕴特征的挖掘方法，以此为基础构建零水印，并采用多重水印算法的思想，确保矢量地图无损的情况下，提升水印方案性能；（4）以零比特动态扩展方法思想构建脆弱水印算法，结合鲁棒性零水印，组成功能多样性且数据无损的水印方案等。在项目的支持下，项目组在国内外刊物上发表论文16篇，其中SCI/SSCI论文9篇，获得科研奖励5项，出版学术专著3部，申请或授权发明专利4项。共培养博士后1名，博士生8名，硕士生4名。