The Extraction Of Topographic Patterns Based On Digital Elevation Model

Digital Elevation Model (DEM) records topographic fluctuation changes and in which it contains various topographic construct information including valley lines and ridge lines. As valley lines and ridge lines are boundaries defining topographic fluctuation changes, they are important to topographic research; what's more, valley lines and ridge lines are respectively water collection lines and water divide lines, so they are also of special meaning to engineering application. The research on how to extract valley lines and ridge lines from digital elevation model is one of hot researches in geosciences.According to the type of data resource, the methods for extracting topographic patterns based on digital elevation model are mainly divided in two types: the method for extracting topographic patterns based on Grid data and the method for extracting topographic patterns based on Contour data. The paper discusses these two methods in precedence.In the study of the method for extracting topographic patterns based on Grid data, the author introduces the terrain profile analysis method and the falling water simulations method. In the terrain profile analysis method, as feature lines which are generated by the traditional terrain profile analysis method are of the problems of fragmentary,parallel and crossing, we optimize the traditional method by adding the following conditions" the neighborhood unused feature points which are around the used points are set used points&feature lines are screened by their length and their scope". By doing these, we successfully solve the exiting problems in the traditional terrain profile analysis method. In the falling water simulations method, the author uses the ArcGIS software to illustrate the procedure of feature lines extraction, and simply discusses advantages and disadvantages of this method.In the study of the method for extracting topographic patterns based on Contour, the author extends research in three aspects according to feature points' extraction, feature points' judgment and feature lines' connection: discusses different methods for feature points extraction; distinguishes valley points and ridge points in different...