利用地理坐标网分块的矢量地图脆弱水印方案

A Fragile Watermarking Scheme for Vector Map Data Using Geographic Graticule Block-Wise Method

为解决矢量地图数据的完整性认证问题,提出一种利用地理坐标网分块的脆弱水印方案.首先利用地理坐标网按照一定的经差和纬差将矢量地图划分为互不重叠的数据子块,然后对每个子块内的数据点进行排序处理,利用嵌入位前的坐标信息生成脆弱水印,最后采用防数据点溢出策略通过修改坐标嵌入位将认证信息嵌入.水印检测与嵌入过程相对应,无需借助原始数据.数据认证时,通过对比检测出水印和生成水印的一致性,判断地图数据是否遭到了篡改.采用某地1:100万的道路线状数据进行水印性能评估实验,实验结果表明,该脆弱水印方案具有良好的稳定性、不可见性和篡改定位精度,能够对矢量地图数据的完整性进行准确认证.

To solve the problem of vector map data integrity authentication,a fragile watermarking scheme using geographic graticule block-wise method is proposed.Initially,the whole vector map is divided into non-overlapping data subblocks by means of geographic graticule according to certain longitude difference and latitude difference.Then vertices in each subblock are sorted,and fragile watermarking is generated by utilizing the coordinate information before the embedding place.Finally,a vertice anti-overflow strategy is adopted to embed the authentication information through modifying the embedding digits of coordinates.Watermarking detection corresponds to the embedding procedure and does not require the participation of original vector map data.During the data authentication process,whether the map data has been tampered could be determined by comparing the consistency of the extracted watermarking with the generated watermarking.A road-linear data with a scale of 1:1 000 000 was adopted to evaluate the performance of the proposed scheme.Experimental results show that the proposed fragile watermarking scheme has satisfactory stability,imperceptibility and tamper localization ability.Therefore,the scheme is capable of authenticating the integrity of vector map data accurately.