Precision Three-dimensional Scene Modeling And Research Of3D WebGIS Visualization Technology

With the Geographic Information System (GIS) from two-dimensional (2D) to three-dimensional(3D), visualization of three-dimensional space has become an important research trend of GIS. The network is one of the most effective means to achieve data sharing. The construction of Web-based Geographic Information System (WebGIS) and the realization of three-dimensional visualization are signifieant to data sharing and the reproduction of three-dimensional scene.3DGIS and WebGIS are both two important trends for the development of GIS, each of which has a more mature technology systems and applications. Visualization of3D WebGIS combined with three-dimensional modeling techniques and network three-dimensional technology, is the current research focus for field of GIS.The thesis studies the issues related to precision three-dimensional scene modeling and visualization of three-dimensional WebGIS based on VRML standard. The main research works are as follows:1. Three-dimensional geographic information visualization techniques are studied, with emphasis on the theory and technology of three-dimensional terrain modeling and three-dimensional feature modeling. Related software, the thesis has carried out down-to-earth study and practice on data capturing, data processing and model optimization in the proeess of three-dimensional modeling.2. According to the fact that the feature model and terrain model does not match in precision three-dimensional scene, a solution of the features and terrain matching is proposed. Through large-scale terraforming, embedded feature constraints in the Delaunay Triangulation to achieve seamless integration of the featuret and terrain. And this method can weaken the phenomenon of terrain mutations may occur after the match thought local correction of the terrain surrounding feature.3. The principles and methods of using the VRML standard to achieve Three-dimensional network visualization are studied. The technology roadmap of achieving three-dimensional WebGIS visualization based on VRML plugin is proposed and verified by experiments. The method of increasing system speed and reducing the network load by VRML file optimization is elaborated and the effectiveness of the method is ascertained by a practical example.