Research On 3D Visualization System For Geological Information

With the steady progress of the construction of Digital City, coupled with the high-paced development of technologies like computer science and graphics, there is a growing need to effectively manage various kinds of information below the surface of the earth such as geological data, underground buildings and pipelines data, and so on. Geological data, however, is especially important in the course of urban management and construction. Cities suffer from earthquake, ground subsidence, landslide and karsts-rock subsidence to different extent due to different geological zones on which they are located. Therefore, great efforts are being made by governments from many cities to try to forecast and prevent the occurrence of these geological disasters based on their geological data on hand. Moreover, many fields in urban construction such as subterranean project, water and electricity project, traffic project, environment project and exploitation of resource need geological data to prove the feasibility of running a project. For these reasons, it is quite urgent to manage, analyze and display geological data by the help of Geographic Information System(GIS) and its relevant technologies. However, 2D GIS at present have difficulties in managing and representing geological information due to the complexity and unstableness of geological entity. In order to present complex and tremendous volumes of geological information to users in a direct way, a 3D geological visualization and management system should be established based on technologies like modeling, 3D visualization and database. By deploying such a system, information services about geological information will be provided for urban construction, development and management; geologic resources will be effectively managed and monitored by specialists working in geology; the research on the development and evolution of geologic architecture will be assisted.This paper is based on the author's ponderation on 3D visualization of geological information, combined with the work in the research on Visualization and Modeling the 3D Quaternary and Construction Frame in the Object Region sponsored by Hangzhou Earthquake Administration, Bureau of Hangzhou Science & Technology. A systematic probe into the 3D visualization of geological information is made, which covers several topics like 3D modeling method for geological entity, principle of computer 3D visualization, systematic and functional framework of 3D geological visualization system, and key techniques for 3D visualization of geological information. Afterward, a 3D geological visualization system is realized to prove the theories and methods discussed in this paper.In general, this paper covers contents from the following 6 chapters:In chapter 1, the meaning of writing this paper, the current researching status of 3D visualization of geological information and the researching methods adopted in this paper will be discussed.In chapter 2, emphasis will be put on methods for generating 3D models of geological information. First, a general process of modeling geological information will be proposed. As an integral part during this process, surface fitting and some of its methods will be described. Then, the author will use ArcGIS, a popular GIS software to model the 3D geological surface of Hangzhou. However, Using ArcGIS to model a given geological entity has several disadvantages, one of which is that it can only generate models representing the surface, not the interior architecture of that entity. Therefore, a method which is able to create entity other than surface modelswill be described. Finally, Schlumberger's geologic modeling software--Petrel willundertake the task of building 3D geological entity model for the city of Hangzhou.In chapter 3, focus will be put on principles of computer 3D visualization. After establishing 3D geological models, a lot of work needs to be done in order to map these 3D models onto a 2D screen. The process of such mapping will involve coordinate systems like model system, world system, viewing system et al as well as the transformation between these coordinate systems. Moreover, in order to maintain the rendering effect and to relieve the burden of graphic processing unit when a computer is dealing with tremendous volume of geological models, a technique called LOD (Level of Detail) should be exploited. The author will have a brief introduction to the principles of LOD, make a few improvements, and propose two solutions suitable to 3D visualization of geological information.In chapter 4, design of a 3D geological visualization system covers the whole chapter. First, the functionalities of the system will be analyzed. Then, it goes to the phase of overall design according to those analytical results, and the overall framework and the functional framework will be proposed. Finally, the author will make a detailed design of the system and its object model.In chapter 5, practice and realization of theories and methods mentioned in previous four chapters make up of the contents. In the course of system development, there are a lot of key techniques which guarantee the success of developing the system. They will be described respectively. In the last section of this paper, the running results of different functions of the 3D geological visualization system will be displayed.In chapter 6, a final conclusion will be drawn, and what should be done in order to make the system perfect will be listed.