The Study On The Extraction Methods Of Terrain Feature Lines

The Digital Elevation Model (DEM), as the basis of the Digital Terrain Analysis,can be analyzed to extract a variety of topographic factors such as slope, curvature,terrain undulation, ridge/valley lines, drainage networks and other topographical featureinformation for further applications in various fields including agriculture, waterconservation, mapping and military. How to design a reasonable and feasible DEMinterpretation algorithm and then obtain effective feature information from huge DEMdata has become an important part of Digital Terrain Analysis.This paper gave an overview about the status of the terrain feature extraction fromthe aspects of type and technique, clarified the importance of the foothill line anddefense line extraction, made these two lines as the main content and offered theextraction algorithms respectively. The work done mainly included the followingaspects.Firstly, aimed at solving the problems that the parameter threshold wasnon-self-adaptive and local static in the existing foothill line extraction methods, basedon the analysis of the topographical features of the foothill region, decomposing theelevation was be done to simulate the contour surface so as to grasp the macroscopicvariation of the slope gradient between the mountains and the plains; combined with theidea of dynamic programming, successively approximating the real and optimal foothillline with iteration split was adopted.Then, in view of the important role of defense line in the construction of militarydeployment, disaster prevention and mitigation, scenic areas’ planning projects, there was not yet a systematical research on the defense line. After analyzing the defenseline’s characteristics, summarizing the definition and nature of it, an extraction planbased on visual analysis was proposed; by establishing reasonable screeningconditions of the candidate feature points, the pseudo feature points was eliminated andthe final feature line was formed.Finally, several reasonable and practicable experiments were done, and theexperimental results were analyzed to verify the validity and applicability of the abovemethods.