The Application Research Of 3D Visualization In GIS

Now, the technique of 3D (three-dimensional) visualization which accords with human physiological habits is one of the popular research directions in computer and information sciences. GIS as a new-fashioned information system provided of powerful functions and comprehensive applicability, the technique of 3D visualization must be imported in order to make GIS carrying on well and satisfying the users.Since 1998, the concept of DE (Digital Earth) which has aroused a tide in the world was brought forward by the vice president of the United States Gale. It is a global strategetic plan and is full of far-reaching political meaning and economic background. Thereafter, the development of VR (Virtual Reality) technique, which was a synthesis of multiform technology including multimedia, visualization and GIS etc., lead to another new tide in scientific domain. The research of amalgamation about the technique of 3D visualization and GIS has an unusual significance. Based on this, the application research of 3D visualization in GIS was mainly focus on this paper. The research is one part of the research project "VR technique in Geoscience transect and the dynamic simulation of the lithosphere inversion" funded by Education Ministry.The research found that the current 3DGIS software couldn't be used to undertake the applications. The functions of visualization in commercial GIS soft is so poor and the analysis functions in RS soft are so shortage that these software are limited to surface model simulating the terrain and they can't be used to obtain the inside information of spatial volume.Based on the analyzing and researching the abundant information, the application of 3D visualization in GIS was systematically discussed in the thesis. Firstly, the development and application of 3D visualization in GIS were described. The 3DGIS in which the 3D technique was imported was expounded synthetically. And the interrelated techniques including data structure, model, and so on, were discussed. Secondly, the technique of 3D terrain visualization wasexplored in detail, which is the primary application in 3DGIS. The spatial data structure, the surface modeling and the arithmetic were analyzed concretely. The technique of volume visualization and the realization arithmetic were compared and analyzed too. The technique of volume visualization is a technique that can discern the inner information of spatial volume. Finally, the common designing techniques of the visualization system such as Object Oriented and COM, and four developing toolkits were summarized, compared and analyzed. IDL, which is one kind of objected-oriented programming toolkits and owns a great many functions, was used to develop the visualization systems. The first system is designed for realizing 3D terrain visualization based on texture mapping. The second system is designed for realizing 3D volume visualization based on direct volume element. And some application demonstrations were given in the thesis.The two systems were summarized as follow.The system of 3D terrain visualization is called Virtual Scene Generate System. In the system, the data of DEM can be displayed through visualization technique and texture map can be covered on DEM to generate the vivid terrain environment. Users can browser, operate the environment, such as zooming, moving, rotating, and controlling the display properties like terrain undulation, environmental ray, background and so on. Besides, the data of DEM was utilized to fulfill the functions of analysis, such as character analysis of terrain, visibility analysis and gradient analysis etc. As a module of GIS, the system can be used to query spatial coordinates, factors of terrain, and to show elevation database. The flying, walk simulating, submerging and creating movie are a trait of this system. In addition to these, this system can show DEM as a scenograph, which can generate colorful picture, contour, density histogram. Another peculiar function is to observe corresponding 3D model by selecting a region on 2D picture.