GIS Park

Terrain is the carrier of Virtual Geographic Environment(VGE). In VGE,the purpose of modeling is not only restoring geographic elements such as terrain but also construcing the high level interactive channels for human beings and VGE.However, due to the massive, regional and multi-dimensionally structural spatial data character, which is peculiar to terrain, it’s difficult to implement real-time and real terrain modeling in VGE. Meanwhile,spatial analysis is a special function in GIS, so how to implement the spatial analysis directly facing VGE and provide decision support for the action between human beings and geography is one of the most concerned topics in GIS currently. Based on the background above, the kit of terrain modeling and analysis visually has been developed with the main thread—the terrain real-time modeling in VGE and the kernel topic—implementing real-time and interactive edit and analysis of the terrain models. This paper is concerned with what are listed as follows. 1. Laying stress on VGE and terrain modeling as well as spatial index and spatial analysis, the paper reviews the current research development involved,then proposes the fundamental framework of terrain modeling and analysis in VGE. 2. Based on the previous work, the algorithm of creating TIN expressed by delaunay triangulations is introduced and implemented with the method based on the spatial index of quadtree and convex. It’s proved in practice that the calculating time of this algorithm rises approximately to the linearity with the expanding scale of problems.In the same hardware condition, the runtime using quadtree to cut the point set is far shorter than using traditional method. 3. With the spatial index of quadtree, the approach to interactive query, edit and modify for point, line and surface in TIN is discussed. 4. The way to three-dimension spatial analysis based on TIN is studied, and the results are visualized. The typical spatial analyses include viewshed analysis, submergence analysis, section analysis, slope and aspect analysis and contour lines automatical extraction. And with the demonstrational geographic elements of road and forest, the road design is realized and the constructional method of virtual forest environment is mentioned based on TIN. 5. The research results above integrated, the kit of terrain modeling and analysis visually has been developed in junction with Visual C++6.0 and OpenGL.