Terrain Data 3D Visualization And Compression

The visualization of three-dimension (3D) terrain surface is a hot research topic in geographic information system (GIS), digital photogrammetry (DP), virtual reality (VR) and other associated fields. With the development and innovation of computer science, computer graphics and modern mathematics theory, some new research directions, such as virtual reality (VR) and scientific visualization (SV), are attracting more and more researchers. Additionally, terrain data are becoming larger and larger along with the increase of resolution. Therefore research on compression of terrain data is of great importance.The research on visualization of terrain falls into two parts: visualization of surface and visualization of underground space. In terms of surface visualization, the 3D visualization of large extension terrain and the real-time wander in virtual city scene are discussed. In terms of visualization of underground space, surface reconstruction from planar contours and volume rendering are discussed. Subsequently, the realization of a 3D underground geologic demonstration system is given.In respect of compression of terrain, an optimized SPIHT algorithm for terrain image compression based on wavelet packet is presented. Wavelet packet analysis decomposes the upper frequency bands as well as the lower ones to suit the energy specialty of the terrain image. The Set Partitioning in Hierarchical Trees Algorithm (SPIHT) is employed to quantize the wavelet coefficients. And the algorithm is optimized for its "Continuous Zero Problem".