Study On Lossless Digital Watermarking Algorithm For Vector MAP Based On Space Feature

As an important part of the geographical spatial data,vector map data occupies an important position in the national economic construction and national defense security.With the wide use of vector map,the map is easy to be tampered and copied in the process of distribution and transmission,which can cause a serious loss to national security and data producers.Therefore,the copyright protection and integrity authentication of vector map data is increasingly serious.As one of the important technologies of digital product safety certification,digital watermarking technology has been made great progress in the vector map data.But because vector map data is very demanding for the data accuracy and needs high fidelity data in some special occasions,the research of vector map lossless digital watermarking technology has more theoretical significance and practical value.Based on the polyline metadata model of 2-dimensional vector map data,the lossless watermarking framework model is analyzed and how to improve the capacity of reversible watermarking algorithm and robustness of zero watermarking algorithm is solved in this paper.Firstly,the digital watermarking technology is introduced,and the vector map data model and spatial characteristics are analyzed.Combined with the digital watermark attack technology,common attack means of vector maps and quality evaluation method of algorithm are summarized and concluded.Secondly on this basis,two kinds of lossless watermarking algorithms are proposed.The one is differential expansion reversible watermarking algorithm based on QR codes.It makes QR codes act as carrier of watermark information and improves the amount of effective embedded watermark information to some extent by using each polyline metadata orthocenter to construct difference sequence.The other one is zero watermarking algorithm based on DWT-SVD.It utilizes Douglas-Peucker compression algorithm to extract feature points of polyline metadata,then adopts the low frequency wavelets of discrete wavelet transform techniques to construct the feature points of zero-watermarking parameters and uses the first two singular value of singular value decomposition to construct the non-feature points of zero watermarking parameters.And to against IBM attack problems,we introduce the third-party certification,which improves the robustness of zero watermarking algorithm.Finally,based on the above two kinds of lossless watermarking algorithm,a vector map lossless watermarking prototype system is designed by open source QGIS.Through actual test,the software can satisfy the business enterprise to protect copyright and test data integrity,so it has upper value of practicality and popularization.