A blind watermarking method for CityGML

Abstract

We propose a blind watermarking method for CityGML in this paper. Firstly, we parse the CityGML text file and select the virtual 3D city model for watermarking. Secondly, we transform the model by using geometric invariance. Then, we transform the Cartesian coordinate to the Spherical coordinate to obtain the sphere radii of each vertex. Finally, we insert the watermark by altering the DCT coefficients of the sphere radii segment. We conduct several experiments using different parameters to explore the watermark payload. The method can embed 64 bits watermark into a CityGML model. In addition, it shows good robustness against adding noise, rotation, uniform scaling, translation, and vertices reordering attacks. However, it still has drawbacks under cropping and simplification attacks.