Research On The Fast Construction Method Of 3D Geographic Scene Based On Large Scale Topographic Map

Recently, the development of computer hardware technology greatly enhances the capacity, speed and precision of computer graphic/image processing, and promotes the development of human beings on geospatial information collection, organization, processing, expression and other techniques. With the continuous progress of 3-D space modeling, virtual reality and 3-D visualization, compared to the traditional planar electronic map in modern cartography, the representation and application of 3-D electronic map which has more intuitive and rich information has got a high concern and has been one of the research hotspots.However, the richness of geo-information influences the efficiency of 3-D geographic scene modeling. Traditionally, although the one-by-one modeling method which emphasizes the geometric details of geographic entities can obtain a very vivid 3-D geographic scene, it is often difficult to adapt to the rapid requirement for large-scale scene to be constructed in geographic analysis. Considering the spatial distribution, shape and attributive information of geographic objects in topographic map, this thesis selects the large-scale topographic maps whose scales are between 1:500 and 1:2000 as the basic data, makes terrain, residential area, road, vegetation and river as the main geographic features, combines the thematic information being obtained through the other means and discusses the rapid construction methods of 3-D geographic scene. Based on Visual C++ 6.0 and the API of OpenGL, a prototype system of rapidly constructing 3-D geographic scene, which is based on large-scale topographic map and considers the spatial combination relation between other geographic objects and 3-D terrain, is designed and developed through object-oriented programming. In the aspect of 3-D terrain generation, TIN data are built by means of dispersing the contour lines and elevation points, then the regular square grid (RSG) DEM is obtained through elevation interpolation and the quadtree structure is organized for the multi-resolution terrain; In the aspect of geographic object modeling, this thesis analyzes and discusses the rapid construction techniques of large-scope geographic object models according to the cartographic characters of different geographic features and adopting the methods of combining spatial data and attributive data; Based on the above mentioned, the seamless integration methods of 3-D geographic objects and 3-D terrain are discussed with spatial data syncretizing technology; In the aspect of design and development of the experimental system, based on the integration of spatial data and attributive data of geographic features, a three-layer architecture including data layer, model layer and interaction layer is adopted to design and develop the prototype system according to the software engineering thought. Finally, some rapid construction experiments of 3-D geographic scene are done to demonstrate the research methods, which are based on large-scale topographic map.