Watermarking Algorithms for GIS Vector Data Considering Geometrical Characteristics and Topological Relationships
|School||Nanjing Normal University|
|Course||Cartography and Geographic Information Systems|
|Keywords||GIS vector data watermarking algorithm geometric features topological relationship quality inspection|
With the rapid development of computer technology and the increasing popularity of the internet, all kinds of media contents are converted into digital forms to improve the efficiency and accuracy of information expression. As a kind of digital products, the copyright protection of GIS vector data is more important for its higher cost of producing and updating, wide range of applications and high accuracy requirements. As an important method of copyright protection, digital watermarking algorithms used in GIS vector data should not only meet the general demands but also meet the demands of high accuracy and imperceptive. This paper is supported by The HI-TECH Research and Development Program of China (863 Program)—Research on Key Technique for Copyright Protection of GIS Vector Data (NO.2006AA12Z222). On the basis of concluding element characteristics of GIS vector data, this paper designs and realizes two algorithms which considering element characteristics and topological relationships and presents a method for inspecting the quality of watermarked GIS vector data. The major contents of studying and conclusions of this dissertation are as follows:(1) The characteristics and topological relationships of GIS vector data are summarized and analyzed. The important elements are classified and then the semantic characteristics of GIS vector data from shape invariance, area invariance and topological relationship invariance are concluded.(2) A watermarking algorithm by adding proportion points into carrier data is designed and realized. By adding proportion points into line features or surface features, the binary copyright mark could be embedded into carrier data. The algorithm is easy to realize and could resist zoom attack, translation attack, rotation attack and adding noise attack, but has less robustness of shearing attack and compression attack.(3) A watermarking algorithm based on disjointing relationship of two polygons is designed and realized. In this algorithm, each polygon is regarded as an object. Firstly, the ID of each object is calculated and objects are sorted by ID, then the closer two objects are divided into one group, at last copyright mark can be embedded into the disjointing distance of each group. This algorithm embeds copyright mark by moving the polygon instead of moving the nodes of the polygon, which could effectively keep the geometrical characteristics of polygon elements. The algorithm has good robustness that could resist zoom attack, translation attack, rotation attack, delete data attack and add data attack.(4) A method of inspecting the quality of watermarked GIS vector data is presented. In this paper, according to the polygon elements such as habitation data, the influences are concluded to the characteristics of GIS vector data after watermarking embedding. A GIS vector data quality inspection method is designed and realized from the aspects of coordinates precision, polygon closure, polygon shape consistency, topological relationship consistency and so on.The paper remedies the defects of watermarking algorithms in keeping element characteristics and topological relationships of GIS vector data to some extent. And a method of inspecting fidelity of watermarking algorithms is presented. This research could promote the application of copyright protection for GIS vector data.