Terrain Data Compression And Walkthrough

With the extensive application of Geographic Information System (GIS), 2D GIS couldn't meet the practical needs any longer. People want to visualize and analyze their three-dimensional data. However, visualization of terrain is inevitable during the course of building 3D GIS. Additionally, terrain data are becoming larger and larger along with the increase of accuracy. Therefore researches on compression of terrain image are of great importance.The researches in this paper fall into two parts: compression of terrain image and walkthrough of 3D data. In terms of compression of terrain image, with comparison and analysis in the selection of some typical wavelets, a way of terrain's compression is realized based on Antonini9/7 wavelet and EZW algorithm in this paper, and the filters of Antonini9/7 has been improved. Furthermore, a novel still terrain's image compression algorithm is introduced based on the terrain's change. The algorithm encodes the image with a better quality inside the region of interests, and does it with a low-grade quality in the unimportant region (outside the region of interests). Under the limited storage space condition, the image encoded by the algorithm not only meets the limit of the storage space, but also ensures the reconstructed image with a better quality. In terms of walkthrough of 3D data, the conventional roam algorithm has been improved in two aspects: error estimation and crack eliminating. By the improved algorithm walkthrough is realized and the terrain's resolution has been increased greatly. And this method has been reached to handle larger data and make interactive terrain walkthroughs on PC platform.