Research And Development Of 3D Visualization System For Geological Surveys

With the development of computer graphics, mathematics, geology, visualization in scientific computing and virtual reality technology, great progress has been made in 3D visualization and analysis techniques which have been widely applied to urban planning, engineering construction, resources surveys, geological surveys, environmental monitoring, disaster prevention, and many other fields. In the dissertation, the objectives of our study focused on the applications of 3D visualization and analysis techniques in geological surveys. 3D visualization for terrain information and geological information is regarded as the technological breakthrough point for the research goal. Based on intensive study of the basic theories and algorithms of 3D visualization for terrain and geological body, and combined with the author's experience from the relevant projects, as well as relevant research results of other researchers, some improved algorithms have been proposed. Meanwhile, a prototype system related to 3D visualization for geological surveys is implemented. The main study contents of the dissertation are as follows:(1)A 3D visualization and analysis system for geological surveys is developed, which possesses the independent intellectual property rights. The system is constructed with two subsystems which are related to the 3D visualization for terrain and geological body respectively.(2)In the course of implementing 3D terrain visualization, we deeply studied the 3D terrain modeling techniques and the construction of the terrain TIN model based on Delaunay-TIN. In the generation of Delaunay-TIN, we adopted a new approach which integrated the partition algorithm and the triangulation-nets-growth method, consequently both the system cost and time performance are taken into account.(3)In order to implement the simplification and the multiresolution presentation of the terrain model, we deeply studied the quadtree LOD algorithm and ROAM LOD algorithm. Some effective improvements have been made. Users can freely roam 3D landscapes and simulate flight in multiple control modes without any delay.(4)For 3D modeling of geological body, a new modeling algorithm with Generalized Tri-Prism (GTP) model is proposed. It can achieve 3D geological modeling under more complex geological conditions, such as stratum missing, strata pinching, lens body, fault or thrust fault, etc. In the algorithm, a new conception called controlling dummy-borehole-chain is given, and the integrity of controlling dummy-borehole-chain is maintained through constrained-Delaunay-triangulation, therefore, complex geological modeling can be realized.(5)In order to get more accurate geological model, a new borehole interpolation algorithm is proposed, which can generate more intensive borehole data set to create good conditions for the optimization of the model.(6)After assimilating many research achievements, such as model cutting algorithm, profile generating algorithm, and 3D interactive technology, etc., the subsystem for the 3D visualization of geological body has powerful functions of 3D visualization and analysis on geological model. It can perform a series of visual analysis operations, such as zooming model, roaming, getting geological profile, digging, adjusting transparency, uncovering stratum, generating fence map.The research of the dissertation preliminary implemented 3D visualization and analysis for the information of geological surveys. This has great practical significance for geological surveys and can accelerate its pace in the informatization and modernization process. On the earth's surface, 3D visualization for terrain information can expand people's observing vision and imagining space. By using remote sensing images as the texture of terrain, we can create a virtual environment in which geological workers can vividly accomplish geological information extraction, geological structure interpretation and comprehensive assessment for engineering construction, disaster prevention, resources surveys, etc.. By this means, the geological surveys can be carried out even in adverse geographical environment. Below the surface of the earth, 3D visualization for information of geological body can restore the structure of geological body, the conformation characteristics and spatial distribution. This can help geological workers to observe and analyse geological structure in depth. Through visual analysis, geological workers can do further studies on geological objects and understand the relation between their internal information and surrouding geological environment. Furthermore, visual analysis operations can be done on the geological objects, such as zooming model, roaming, getting geological profile, visual digging, uncovering stratum, generating fence map. Therefore, the system provides strong surpport to further quantitative analysis, exploration and application for the geological information.