Research On The Digital Watermarking Algorithms For DEM

Digital elevation model(DEM)is an important component of geospatial data.It has been widely used in surveying and mapping,geology,mine engineering,battlefield simulation and so on.However,the digital form of DEM for the convenience of the terrain simulation analysis at the same time,due to its characteristic of easy storage,modify,communication,make it easier for DEM tampering,infringement,copyright disputes arising from the increasingly serious.Therefore,how to make the DEM data share reasonably and effectively protect the owner's copyright interests has become a pressing and realistic problem.At present,digital watermarking technology has become an important means of copyright protection of geospatial data,and provides a feasible technical approach for DEM copyright protection research.This paper according to the characteristics of the data structure of DEM,combined with the requirements of the characteristics and applications of the digital watermarking algorithm,digital watermarking algorithm based on grid and triangulated irregular network of two types of DEM data were analyzed.The main research results are summarized as follows:(1)The characteristics and requirements of DEM digital watermarking are analyzed and studied.This paper summarizes the current research status of DEM digital watermarking algorithm,and introduces the data structure and watermarking algorithm characteristics of two types of DEM,regular grid and triangulated irregular network respectively.Analysis of the two types of DEM data most often suffer from watermark attack methods and data processing methods,combined with the requirements of topographic features,data error and application error of two types of DEM digital watermarking technology requirements are summarized,and provide a theoretical basis for the construction of the target DEM digital watermarking algorithm.(2)This paper propose a blind watermarking algorithm for grid DEM that can effectively resist elevation translations and cropping attacks.Elevation translations and cropping are the common means of attack for DEM data watermark.The algorithm takes fully account of the characteristics of DEM data.The original watermark information is processed by the mechanism of spectrum spread in order to forming corresponding relationship with elevation difference.Using the invariant feature of elevation difference of adjacent grids in attacking of elevation translations,embedding the value of the watermark to elevation difference one by one by quantification manner.Then,allocating the ectatic difference to the next character of the adjacent elevation.The experiments show that the algorithm has good invisibility and less effect on the original DEM as well as robustness in resisting elevation translations and cropping attacks.(3)A blind triangulation watermarking algorithm using feature points is proposed in this paper.Analysis of triangulated irregular network DEM data structure,the most often suffers from the simplified attack and cutting attack two watermark attack types,combined with topographic features,using triangle irregular network DEM sparse feature extraction techniques with the characteristics of triangular mesh node,triangular mesh node as the watermark information into the carrier.The node coordinates are enlarged and the effective bit is used as the watermark mapping vector.According to the error control principle,the watermark is embedded into the appropriate coordinate position by quantization.When extracting watermark,the voting principle is adopted,and the original data is not needed.The experimental results show that the proposed watermarking algorithm for DEM data accuracy and precision application effect is smaller,has good transparency,resistance to attack and simplify the cutting attack robustness,good error control,and ensure the realization of the embedded watermark and the good robustness to the embedding error cost less.