Research On Key Technologies Of CityGML-Based 3D GIS

3D GIS is employed in an increasing number of applications. Compared to traditional 2D GIS, 3D GIS reflects the information of the real geographic environment better. It provides more friendly ways for interaction and has capabilities of analyzing 3D spatial information. 3D GIS is becoming the hot reaseach field of current GIS study and it has great potential in future application.However, the current development of 3D GIS is confronted with various issues and challenges. There is no mature model and unified framework for visualization while application departments use their own models and frameworks. It makes the interoperability and data sharing difficult. To solve these problems, Open GIS Consortium (OGC) has developed City Geography Markup Language (CityGML). It provides standard data model for 3D GIS. This thesis focuses on developing 3D GIS based on CityGML and several key technologies are studied. The main work of this dissertation can be conluded as following five parts:1. Thorough research has been made on visualization technologies of CityGML 3D models. A rapid parsing methodology combined with flow-based reading and data-binding is proposed. The multithread strategy is used to accelerate the data loading speed. To improve the performance of 3D rendering, geometry data are converted to direct3d mesh.2. To unify the management of CityGML data, this thesis studied the technologies of creating CityGML database on Oracle Spatial 11g. CityGML database is developed by simplifying CityGML model, derivating database schema and creating the import and export tool. To implement interoperability and data sharing in network environment, approaches for 3D GIS data publication are studied.3. To improve the rendering performance in client, the model for data organization is studied. Pyramid model is applied to the client buffer struct and efficient data dispatch algorithm is proposed.4. 3D GIS spatial analysis is also studied in this thesis. A rapid mouse picking method is proposed to obtain the terrain data under the 3D earth model and some measure functionalities such as distance, azimuth and area measuring are implemented.5. Finally, the design and implementation of CityGML-based 3D GIS prototype is discussed. The prototype implemented visualization, database management and network data publication, as well as the organization and dispatch of the client buffering data. It also can be employed to other applications as a fundamental platform.