Multi-scale Seamless Visualization of the Global Terrain Based on DQG

摘要

Real-time and seamless visualization of the Earth terrain based on Global Discrete Grids is a subject of considerable current attention. In this paper a multi-scales visualization model of the global terrain based on DQG (Degenerate Quadtree Grid) is approached. Our approach starts with a partition method, called Degenerate Quadtree Grid (DQG) and an encoding scheme of the corresponding grids is introduced briefly. Next, a multiple level of detail model related to viewpoint is presented. In this model, a criterion of terrain model simplification based on viewpoint and roughness of the degenerate quadtree node is developed. Then, making full use of the characteristics of quadtree structure, the cracks within quadtree blocks are induced by simplification. Thus, the cracks splicing are all seamless. In the end, the experiment and analysis are made with the global terrain data, GTOPO30. The results illustrate that: (1) the global terrain based on the DQG is seamless, hierarchical, and regular over the whole Earth; (2) the quantity of global DEM data can be reduced significantly; (3) the visual effect of the global multi-scale terrain is seamless by the model simplification ensuring the accuracy and efficiency of the terrain display.