Research On Digital Watermarking Of 2D Vector Map Based On Content Feature

With the fast development of information processing technology and network techniques, digital vector map has becoming the necessary resource being widely used in GIS, intelligent transport system, digital city, digital national defense construction and so on. Digital vector map has great economical value and strategy significance for its accurate content. And its fabricating cost is huge. On the other hand, illegal copying and stealing of digital vector map are becoming increasingly rampant. A lower level security of it will cause enterprises'losses and even bring risks to national security. As a result, the security problem has attracted our government, military and science research institution's attention. Digital watermarking technology is a common scheme to secure the copyright of digital vector map.The research on digital watermarking for digital vector map has lasted for about 20 years and many schemes have been proposed to solve some kinds of security problems of it. But these schemes have not fully considered the data characteristic of digital vector map and the particular operations on it.The content characteristic of digital maps has been discussed in the paper. The author has studied the security of data in digital maps and techniques that can losslessly recover watermark information, resist some attacks and trace the source maps have been proposed. The main innovative points are the following:Firstly, a lossless digital watermarking algorithm based on attribute information has been presented based on the location information and coordinate information of vertex in vector maps. With the knowledge of data structure and file structure of digital vector maps, its attribute information has been presented in detail and a lossless scheme with zero-bit dynamical extension has been proposed. On the basis of this, space clustering analysis with grid density was used to increase robustness of the scheme.Secondly, a digital watermark algorithm based on spatial characteristic has been discussed for the weakness of the first algorithm in resisting attacks of traditional map operations. Utilizing spatial characteristic of lines and polygons, an algorithm based on partial ordering evaluation suitable for lines and an algorithm based on total order substitution suitable for polygons were presented. A mutual authentication scheme has also been presented in order to weaken the isolatism of traditional watermark information. Under the condition of losslessly recovering watermark information, a robust digital watermark scheme was presented which can cope with normal operations of vector maps such as curve simulation, format transformation, precision reduction, data compression and so on.Finally, utilizing fingerprint recognition technology, a digital watermarking algorithm for digital maps which can be used in personal identification has been presented. The source of digital vector map and the responsible party can be traced with this scheme. High identification rate of digital fingerprint watermark was achieved with the adaptive fingerprint characteristic extraction scheme based on bigraph fractal theory. A zero watermark compensation scheme has been presented based on spatial characteristic digital watermark schemes. To insure the correctness and reliability of personal identification, a three layer watermark extraction scheme was presented with spatial, attribute information and zero watermark. Zero watermark can alleviate the risk of calssification in some degree and provides a basis for beforehand digital watermark algorithm research.