Research On Digital Watermarking Technology Of Electronic Chart

With the development of information technology,geo spatial data has become a widely concerned information resource.Electronic chart,as one kind of geographical space resources,plays a very important role in the national economy and national defense construction.But there are many security problems in the process of the spread and use of electronic charts.Including copyright protection,authenticity identification,source tracking,etc.The traditional digital watermarking algorithm mainly through the discussions the map spatial or frequency domain,and then embeds the watermark information in it.Electronic chart is a kind of map which requires high data precision,but the traditional method is more disturbing to the chart data,so this paper introduces the technology of lossless digital watermarking based on the structure of S-57 standard electronic chart.Lossless digital watermarking technology is mainly divided into:reversible watermarking technology and lossless embedding technology.In this paper,firstly,the content characteristic model of S-57 electronic chart is studied,and then the lossless watermarking technology is divided into:the reversible watermarking technology based on spatial feature and the zero bit extension technology based on gradient algorithm.The detailed analysis and research include the following aspects:First of all,on the basis of introducing the concept of electronic chart and digital watermark,this paper chose S-57 electronic chart as the research object of watermark embedding.On the basis of analyzing the data structure,file structure and content characteristic model of electronic chart,this paper puts forward a framework model of digital watermarking based on electronic chart.Secondly,according to the spatial structure characteristics of the electronic chart,a reversible watermarking algorithm based on the feature of the chart space is analyzed and studied.The algorithm is based on the spatial evolution process of the chart,and through the method of node group selection,the watermark embedding and extraction are realized.On the basis of the characteristics of the chart,a method of selecting the key nodes in the gradient algorithm is proposed,and a new algorithm is proposed based on the gradient algorithm.Finally,through the comparison of experimental and theoretical analysis,a detailed comparison and verification of the robustness,invisibility,content and other aspects of the zero bit watermarking algorithm based on the gray scale change is carried out in detail.At the same time,it also points out the defects of the watermarking algorithm,which pave the way for future research.