The Research Of Virtual Reality Geographic Information System

Virtual reality technology is the integrated technology which developed at the end of the 20th century. The computer technology is the core of Virtual reality. It is comprised of the multi-disciplinary new and high technologies. It have synthetically utilized some computer technologies such as stereoscopic vision, feedback of touch, fictitious stereo in order to imitate artificial simulation environment of people's behavior just like looking, hearing, moving etc. So virtual reality technology has the characteristics of immersion, interaction, imagination, apperceiving, independence.Virtual GIS is a new generation of GIS. It combines three-dimensional GIS, visual technology and virtual reality technology. Virtual GIS can support create complicated virtual figure space and support user adopt many kinds of mutual apparatus to mutual with figure space while offering strong modeling ability of multidimensional data and managerial ability of multidimensional space data. The key of the development of VRGIS is that data management, analysis and graphical display of three-dimensional space of VRGIS.Three-dimensional space data reflects the earth's surface objects and the space information of the environment, such as inherent geographical position, physique characteristic, interaction. Space data model is the theoretical foundation of describing GIS space data organization and designing database which carries on space data. Compared with 2D GIS space data model, the 3D model can be divided to four types that are tessellating model, vector model, hybrid model and analytical model.Digital Terrain Model is a general designation of space topographical data set, and it is the digital description with the figure of space position and topographical attributive character. It is called the digital elevation model whose attribute is elevation in DTM. In the visual aspect of 3D model, choosing the suitable level of detail model(LOD) can reach optimum of the speed of drawing the geometric modeland texture mapping in order to not lose necessary displaying information.This thesis is based on theoretical research of visual technology ofthree-dimension in the geographical information system, including the acquisition of three-dimensional space data, three-dimensional data model, Digital Terrain Model, Digital Elevation Mode and the expression of levels of detail of 3D space data and three-dimensional data visual expression ,etc. I used the function of OpenGL like texture mapping and illumination treatment, and advanced program language Delphi to construct virtual reality topographical scene, realize the interactive operation just like zooming in, zooming out,, rotating and roaming, construct the geographical information system of fictitious reality.