Research On Organization And Visualization Of Global Terrain Data Oriented To Marine Application

With the concept of "Digital Earth" and "Digital Ocean" proposed, people pay more and more attention on organization and visualization of global terrain data. It has become a pressing demand that how to build a global terrain visualization scene with highly reality and efficiency. In recent years, A variety of excellent terrain rendering algorithm have been proposed from all over the world, but most of the research object are land, plane terrain or a small piece terrain, which covers few area. It cannot be effective to meet the needs of various marine products of multi-source and multi-structure data. China is a large maritime country. China has already put "Digital Ocean" into the development programme of marine science and technology as a long-term strategy. As the proceeding of this programme, building global terrain visualization system oriented to marine application has become increasingly pressing.Concerning the characteristics of digital marine application, this thesis focuses on the key technologies of global terrain data organization and visualization, with the purpose of constrcting a integrated visualization system of land-sea, plane-sphere and local-global. The main work and contribution are described as follows:(1) Organization and management of global terrain dataA space division method of uniform distribution for global terrain data was proposed after deeply studying and analysis of many spherical division strategies. The terrain data pyramid was built by using quadtree data structure. Based on the serial number, a suitable method of terrain data storage and terrain block nodes selection was designed.(2) Global terrain rendering based on distance-dependentBased on the global terrain data multi-resolution pyramid model, the distance between the observer and the terrain determines the choice of LOD. Terrain block nodes are handled as the basic processing and rendering units. The same vertex buffer object was used for all block nodes triangle patches of scene on GPU. To deal with the cracks between different LOD levels, smooth transition method is used between LOD levels.(3) Implementation of global terrain visualization oriented to marine ApplicationBased on the Organization of global terrain data and the algorithm of distance-dependent global terrain rendering above, this thesis introduces the GPU processing procedures for the algorithm. A global terrain data organization and visualization system is designed and implemented oriented to marine applications. An interactive 3D terrain scheme was put forward, considering the key technical implementation of different map projections switch, elevation interactive modification and terrain matching with geographic vector data.The thesis effectively organizes global terrain data and structure global terrain visualization system, oriented to marine application, based on the virtual reality and visualization of marine platform-i4Ocean render engine, which is independently developed by Ocean University of China. Just as the simulation results show, the system has a good rendering performance, portability and expandability, with the module chooseing plane terrain or global terrain and editing the value of terrain height according to the character of marine data. It can be effective to meet the needs of various marine applications and provide service for national development strategy of "Digital Ocean".