The Study, Based On Digital Elevation Model Of The Vector Data Visualization

Vector data is used to describe accurate relation of spatial, and it's good at quantitative analysis, so vector data is the mainly input of spatial analysis in Geographic Information System; Digital Elevation Model (DEM) is used to describe parameters of terrain, such as slope, grade, and terrain analysis like visibility analysis, drainage area create, so DEM does well in qualitative analysis. In order to have strongpoint of the two, hybrid Geographic Information System has become a research hit. And the key point is how to render complex vector data onto multi-resolution terrain grid in real-time.This paper mainly focuses on the research about the overlay and visualization of 2D vectors and 3D terrain. Based on analysis of existing research, we do our research with a view to the two thoughts which is method based on vector geometry computation and method based on online texture generation; the researching results are as follow:1. Study on the newly advance of terrain visualization, then a comparison of different terrain simplify algorithm is given.2. Based on Real-time Optimal Adapted Mesh (ROAM) algorithm, a newly ROAM algorithm which support overlay of vectors by indexed Split vector data. The base of the algorithm is to compute inflections, then use inflections to do subsection vector data and index it. Then at Real-time, according to the level of detail of current frame to render vector being indexed.3. Based on on-line texture method, using the technology Render-to-Texture, implement dynamic overlay of 2D vector data and 3D terrain.4. Using Memory Map File and Multi-thread dispatch technology, to manage and dispatch large terrain data and texture data.5. Using C++ language and OpenGL Graphic Library to implement the algorithm of 3D terrain analysis and terrain visualization, and this algorithm has become part of vega3DGIS.The research is accomplished in Vega3DGIS, a GIS developed by Institute of Computing Technology, Chinese Academy of Sciences. It is independent intellectual property. And vega3DGIS is a professional tool for VegaGIS platform.