Ridge detection with a drop of water principle

It is important to display effectively 3D terrain maps with features such as ridges [Lopez et al., 1999]. This paper deals with displaying problems of broad and accurate 3D terrain maps with the feature information. As feature extraction methods a discrete Laplace transform method, and the steepest descent line method [Yokoyama et al., 2007] are known. We consider that those methods are insufficient, since the obtained maps are not accurate. In this paper, we modify the steepest descent line method and propose the steepest ascent method (cf. [Cousty et al., 2009]). Furthermore, we apply it and generate the ridge lined entire Japan 3D terrain map with around 4.5 x 107 cells.