Topological Integrity Detection Method Of Vector Geographic Data

With the rapid development of information technology, Geographic Information System(GIS) has been widely applied to urban planning, land use and transportation management. Geographic data, as the kernel of GIS, have been collected and stored from paper to computer, which makes it convenient to use and transmit. At the same time, there are also data security issues, such as geographic data misuse, and malicious tampering, and even wanton dissemination of data. In addition, topological relations of data sets are very important in spatial analysis methods, which will directly affect the results of the data analysis and making a decision. Therefore, a new watermarking method is needed, which can verify the integrity of the topological relations of geographic data before the spatial analysis, and detect whether the topological relations of the geographic objects has been tampered with and find the tampering positions.In order to verifying the topological relations integrity of vector geographic data, this paper, according to the topological relations in geographic data, studies how to detect the topological relationship of vector geographic data through a fragile watermarking method and a public watermarking method, respectively. Two methods are all first generated the watermark information by the disjoint distance of any two disjoint features. In this way, the watermark information will contain the information of the topological relations of features. The main research contents and conclusions of this paper are as follows:(1) In verifying topological integrity of vector geographic data based on fragile watermarking algorithm, the watermark is generated from the disjoint distance between the objects; then the objects are zoomed in or out according to modifying the disjoint distance to embed the watermark. In watermarking detection, the topological integrity of geographic data is determined by the result of matching the regenerated watermark with the extracted watermark. Experimental results demonstrate that it is effective to verify topological integrity of geographic data by the algorithm.(2) A novel public watermarking scheme proposed for verifying topological relations integrity of vector geographic data is aimed to publicly verify the topological relations integrity of vector geographic data. This method generates watermark information through spatial topological relations of geographic objects, then calculates verification code by performing the XOR operation between vertices coordinates and watermark information, and publishes the verification code, so that data users can verify topological relations integrity of the data on a public platform by acquiring public verification code. The experimental results demonstrate that the scheme is effective to verify topological relations integrity of vector geographic and locate the tamper vertices.(3) Design and implement vector geographic data topology integrity verification tool. The tool is based on Visual Studio 2010 development environment, through the MFC framework and Arc GIS Engine’s API to achieve the basic operation of the map. The tool is primarily used to simulate tampering operations of vector geographic data and verify the reliability of the proposed watermarking algorithms.This paper based on the study of topological relations of vector geographic data, through the fragile watermarking algorithm and the public watermarking algorithm, achieves the purpose of verifying the topological relations integrity of vector geographic data. The two algorithms can be reliable and effective to verify vector geographic data topological integrity.