Copyright authentication of digital vector maps based on spatial autocorrelation indices

Digital watermarking is increasingly being used in the copyright authentication of vector maps to prevent misuse and illegal distribution. However, it is difficult to avoid influences on watermarks when undergoing spacial projection transformations, vector data compression, and other common geographic information system (GIS) operations. In this paper, a highly robust copyright-authentication method is proposed for digital vector maps. First, we discuss the descriptive approaches to the geometric characterization of map elements by building the graphical complexity index. Next, using the Moran’s I Coefficient (MC), a type of spatial autocorrelation index (SAI), we effectively integrate the spatial topological information and the spatial geometric shape information into the meaningless zero-watermark, which is robust against common GIS operations. Finally, we generate a meaningful zero-watermark by using the exclusive OR (XOR) process to combine the meaningless zero watermark and useful copyright information, which not only embeds the copyright information but also effectively avoids authentication conflict. These results demonstrate that this method is robust to translation, scaling, compression, rotation and edit operations (robustness is 80%). The robustness suggests that this method can readily support business applications for copyright certification of digital vector maps.