利用多分辨率半边进行全球多分辨率DEM无缝表达

应用传统四叉树结构进行全球多分辨率数字高程模型（digital elevation model，DEM）表达时，不同层次相邻格网间会产生裂缝问题，尽管目前有许多裂缝消除的方法，但大都是属于"后期处理"，且存在诸多限制。为此，引入多分辨率组合映射理论，提出了一种基于多分辨率半边结构的全球多分辨率DEM无缝表达方法。首先给出了基于多分辨率组合映射的多种全球离散格网统一表达方法和裂缝消除原理，并以球面菱形格网为例，提出多分辨率半边编码方法和坐标转换方法；然后，设计并实现了一种全球多分辨率DEM无缝表达算法；最后，应用C++语言和DirectX工具，开发了相应的可视化实验系统。实验结果表明，利用多分辨率半边结构，通过边界结点细分方法的特殊处理，球面菱形格网的四分体内部、边界和极点处均不会产生裂缝。与传统方法相比，该方法从前期的格网剖分结构上解决了多分辨率DEM格网的裂缝问题。

Seamless Expression of Global Multi-resolution DEM Based on Multi-resolution Half-Edges Structure

When performing the multi-resolution DEM expression based on Quad-tree structure, topological crack generates at the meeting of areas of different resolution levels. Holes appear in the mesh between neighboring faces of different refinement depths. Although there are many methods of eliminating the crack, but mostly belong to the "post processing", and there are many restrictions. A new theory of multi-resolution combination maps is introduced, and a seamless expression of global multi-resolution DEM is discussed based on multi-resolution half-edges. The main contents are as follows. Firstly, the unified expression and principle of crack elimination of Global discrete grids are studied based on multi-resolution combination maps, and some methods are put forward based on spherical diamond grids, including encoding and coordinate transformation. Then, seamless expression algorithm is designed and achieved. Finally, by using C++ language and DirectX tools, an experimental system is developed, and the results show that seamless expression of the global multi-resolution DEMs can be carried out with a method of making a tiny adjustment of node subdivision. Compared with the traditional methods, the method in the paper can solve the crack problem from the underlying data structure.