Research On The Optimization Techniques Based On Generalization Of Relief To Digital Relief Shading Map

Relief shading maps express topography by depicting illumination and shadows in differentshades of the tone. The topography in the maps having three dimensions, and in a intuitivemanner. Compared with other methods, relief shading not only give great aesthetic pleasure butalso applied,can profoundly expresses the cartographic region in overall look.However, thereadability of the digital shaded relief maps based on high-precision and high-resolution DEMdata is weakened by intensive and broken terrain details, and its advantages of showing theregularity of topography is inhibited. Therefore, optimizing the effect of digital relief shadingmaps via generalization of relief have become the concern of cartographers.Guided by the experience of manual relief shading, this paper studied the characteristics ofthe generalization of relief in relief shading maps and realize the digital relief shading mapsoptimization techniques based on generalization of relief. It main contain four aspects:1．This paper studied a variety of DEM-based methods to generalize relief, and guided bythe basic principle of generalization of relief in manual relief shading, analyzing the advantagesand disadvantages of digital shaded relief maps using different methods of generalization ofrelief. On this basis, this paper improved and combined the methods of generalization of relief,and proposed the generalization relief method based on PDEs and model based on topographicstructural characteristics to optimize the effect of relief shading map.2．In the cartographic region of structural integrity, this paper build a relief generalizationmodel based on topographic structural characteristics who had the advantage of filteringmethod.This model can enhance the topographic patterns by topographic structural line base onrelief plate which had removed the terrain details by filtering method.It effectively solved thecontradiction between the terrain detail elimination and topographic patterns enhancement. Inorder to ensure the integrity of topographic structural line, the algorithm of topographicstructural point recognition and topographic structural line tracking were improved.3．In the cartographic region of the broken topographical structure, this paper use method ofgeneralization of relief based on PDEs of TV(total variation) model and CDD(curvature drivendiffusion) model to eliminate the terrain details and kept the topographic patterns at the sametime. And the effectiveness of this two models in relief shading maps optimization is anaylized.4．Using digital relief shading program,whose function include draw and edit relief shadingmaps, generalization of relief,and file batching,to make sample maps in different forms of topog--raphy to show the effect of optimization by generalization of relief. And the post-processingtechnology of relief shading map is also studied to improve relief shading maps’ effect.