A New Method for Automatic Extraction of Ridge and Valley Axes from DEM
一种新的山脊线和山谷线自动提取方法

In this paper, a new method for automatic extraction of ridge and valley axes from DEM, named as Directional Profile Approach(DPA), is proposed. DPA can automatically determine whether a grid point in DEM is a possible ridge(or valley) grid point, according to the features of the profiles through this grid point. Applying this new method to extracting ridge and valley axes automatically from DEM, the following several procedures must be accomplished: First, the all elevation grid points which may be located in ridge and valley lines are automatically recognized with DPA. Then the modified Hilditch thinning algorithm is applied to selecting the ridge and valley grid points recognized by DPA. Third, the every two neighboring ridge points or valley points are connected and rudimentary form of the ridge or valley axes is constructed. Finally, the closed triangles in ridge and valley axes are broken and the short branches are removed. A real DEM was used for testing data, the ridge and valley axes extracted automatically by this method can basically represent the topographic features of the corresponding topographical map. Therefore, this new method is effective.