Research On Rich-information & Lossless Watermarking Technology Of Vector Maps

Big spatial data,the main data set of big data,forms the basic framework and spatial datum for describing various geo-objects and phenomena in the era of big data.As the basic component of big spatial data,vector maps are playing a more and more important role in all walks of life in the construction of national economy.On the one hand,vector maps need to make breakthroughs in data opening and sharing to make full use of their own value.On the other hand,the content of vector maps is of high positioning precision and high cost,and the rights of map owners,the sharing of map data and even the national security will be affected in the event of piracy,tampering,illegal dissemination,etc.Accordingly,it is an urgent problem to realize the copyright protection of vector maps in the environment of data sharing.In recent years,digital watermarking technology has been widely applied in the field of copyright protection of vector maps.However,traditional digital watermarking algorithms of vector maps,both spatial domain and transform domain ones,may cause distortions to the original map content to some extent,which can not meet the requirements of some specialized applications.Under this background,lossless watermarking technology has been applied to the field of vector map copyright protection.Taking the lossless watermarking technology of vector maps as the theme,this paper studies on key technologies of lossless watermarking of vector maps,and a series of research has been carried out,aiming at rich-information watermark embedding,enhancing the robustness of lossless watermarking algorithms of vector maps,etc.The main research production in this paper is summarized as follows:(1)On the basis of the analysis of the features of vector maps,this paper has expounded the technical characteristics and frame models of lossless watermarking for vector maps.Based on the analysis of common attacks of vector maps,this paper has summarized the evaluation methods and indexes for lossless watermarking algorithms of vector maps.(2)To improve the robustness of lossless watermarking algorithms of vector maps,this paper has carried out research from two aspects,i.e.,the selection of watermark embedding position and the error correction of watermark extraction results.An ECC-based lossless watermarking algorithm of vector maps has been proposed in this paper.In the proposed algorithm,the copyright watermark data and its corresponding ECC are merged to generate the final watermark data,and watermarks are embedded into polar coordinates of map vertices to enhance the ability of this scheme in resisting operations such as transformation,rotation,etc.,considering the stability of polar coordinates.After watermark extraction,ECC are exploited to detect and correct the error bits in the extracted copyright watermark data,so that the effect of watermark extraction can be optimized.(3)To realize the rich-information wataermark embedding,the method of improving the payload of lossless watermarking algorithms of vector maps is studied in this paper,from the perspective of lossless compressed coding of watermarking image.The characteristics of watermarking images and the common lossless compression methods of images are analysed in this paper,and two lossless watermarking algorithms of vector maps based on compressed coding are proposed.Based on the analysis of the characteristics of watermark images,a compressed coding scheme of watermark image is designed and implemented based on an improved Huffman coding method,and a high-payload lossless watermarking algorithm of vector maps is proposed.In order to enhance the ability of the proposed algorithm to be compatible with different types of watermarking images,a high-payload watermark generation scheme is designed and implemented based on pixel merging within watermarking image,and another high-payload lossless watermarking algorithm of vector maps is then proposed.(4)To realize the rich-information wataermark embedding,a high-payload lossless watermarking algorithm of vector maps is proposed in this paper,based on QR code and polar coordinate conversion.In this algorithm,a QR code is taken as the container of copyright information to generate high-payload watermark data,considering the large information capacity of QR code.And aiming at the problem of small secret key space of Arnold transformation,a scrambling method of watermark images based on double Arnold transformation is designed to enhance the security of the copyright information.Moreover,a method of map vertex grouping and local polar coordinate conversion based on reference vertex is designed to improve the robustness of the watermarking algorithm,which embeds watermark bits into local polar coordinates of map vertices to enhance the robustness of the watermarking algorithm under geometric transformation.(5)To solve the problem of copyright protection in the process of multilevel distribution and multiuser tracking of vector maps,multi-stage watermarking technology of vector maps is studied in this paper,from the aspect of watermark carrier and watermark data respectively.Two multi-stage watermarking algorithms of vector maps are proposed in this paper,i.e.,a multi-stage watermarking algorithm of vector maps based on map vertex grouping and a multi-stage watermarking algorithm of vector maps based on copyright information.The former devides map vertices into several individual groups and constructs the corresponding relationship between watermark data of all stages and vertex groups,and then embeds each stage of watermark data into vertices in the corresponding vertex group,which achieves the independence among all levels of watermark data from the level of carrier of watermark data.The latter realizes the mutual interference among multiple copyrights from the level of watermark data by combining the copyright information at all levels to generate the watermark data.