退化四叉树格网的全球多分辨率DEM无缝表达

为实现全球多分辨率地形快速、高效模拟与可视化表达，探讨基于球面退化四叉树的全球多分辨率DEM无缝建模方法。提出一种基于球面退化四叉树的全球DEM分块建模方法；设计并实现了四叉树块内（相邻节点间相差任意剖分层次）、四又树块间、四叉树与非四叉树块间的自适应无缝拼接算法；应用VC＋＋语言和OpenGL工具，设计开发了相应的可视化试验系统。结果表明：该模型方法可实现全球多分辨率DEM的无缝表达，并在保证精度的同时有效简化了全球DEM格网的数目，简化效率为66．8％（剖分层次为12）。

Seamless Expression of the Global Multi-resolution DEMs Based on Degenerate Quadtree Grids

For realizing simulation and visualization of global multi-resolution terrain efficiently, a seamless modeling method of the global multi-resolution DEM is discussed based on spherical DQG (Degenerate Quadtree Grid) in this paper. The main contents are included as follows: First of all, a new modeling method of global block quadtree based on DQG is developed. Then, an self-adaptable seamless stitching algorithm is designed and achieved, in which the cracks exist within a quadtree block (without limiting the subdivision level of the adjacent nodes), between the different quadtree blocks, or between a quadtree block and a non-quadtree block. Finally, by using VC + + language and OpenGL tools, a relevant experimental visualization system is designed and developed. As a result, the proposed modeling method and the adaptive elimination algorithms of different types of cracks are verified. The experimental results show that the display efficiency of global DEM is improved obviously while ensuring the accuracy of the terrain expression. When the grid was subdivided into 12 levels, the simplification efficiency is 66.8%.