The Technique Of Overlay And Query Based On DLG,DRG,DOM And DEM

With the development of GIS technology and computer graphics , 3D visualization is one of hotspots of current internal and abroadresearch. Cyber-city has become an important field in GIS application. How to utilize the existing 2D data and realize the city 3D visualization are very important to city construction, city planning etc.The paper focuses on visualizing the terrain and overlaying 2D vector data to DEM and building corresponding model of data organization and storage. The overlay of DLG, DOM, DRG and DEM is made by VC++ language and OpenGL graphical library. And several tasks are finished as follows.After reviewing several existing spatial data model, an adapted data model is chosen and an index of spatial data is set up. Using Grid to simulate the surface of earth and overlay DEM with the image texture. Arithmetic of vector overlaying is presented. And this arithmetic uses spatial interpolation to get 3D vector data .Based on the 3D scene, querying the 3d coordinate, querying the attribute of chosen object and controlling walkthrough manually or automatically can be finished.