Research On The Algorithm For Digital Terrain Model Generation And Simplification Based On TIN

With the present of digital-earth concept and comprehensive application of virtual reality technology, Three-Dimension Terrain Model (3D terrain model) as an indispensable part of those is playing a more important role. 3D terrain model is the"framework"of modeling Virtual Terrain Environment (VTE), and it is the basis of analysing and researching on the complicated terrain, and it is also the premise of rendering real terrain scene, exactly expressing the space information correlativity and visualizing spatial analysis result. Establishing 3D terrain model generally based on the real terrain data and high resolution satellite images. The quantity of data is so large that graphics platform can not display large-scale terrain in real-time. In order to solve this problem, researchers have done a lot of work. And most of these work focuses on the creation of irregular triangle network (TIN) and multiresolution terrain models.This paper studies and summarizes the fundamental theories and methods of establishing 3D terrain model. Focusing on the problem of inefficiency about the traditional incremental inserting algorithm, this paper presents VG-incremental inserting algorithm based on the Virtual Grid and provides a new method of optimizing the insertion sequence about the discrete points. As a result, the triangular numbers to be searched and reconstructed can be reduced. The VG-incremental inserting algorithm decreases the time complexity from ( )O n2 to O (n log n) and realizes the TIN terrain model more quickly. All kinds of modeling multiresolution terrain model algorithms are studied and contrasted as well. Aiming at the problems of time inefficiency and some topological characteristic can't be maintained effectively in traditional PM algorithm, an improved PM algorithm is presented through combining quadric error metrics and half angle of vertex normal cone as the rule of mesh simplification to repalce original energy equation of PM algorithm and choosing one vertex of collapse edge as the new vertex position. The improved PM algorithm not only reduces the algorithmic complexity,but also eliminates the ambiguity of progressive mesh, at the same time, recommends how to judge and solve all kinds of the topological characteristics in process of mesh simplification. Furthermore, the method for dealing with the boundary vertexes and edges along with the smallest stack to rank the folded error were used for improving the time efficiency and universal application of the algorithm. The feasibility and the high-efficiency of the algorithm for establishing TIN terrian model as well as the good performance in the efficiency and quality of the improved PM algorithm has been confirmed by the experiments on certain area terrain data of TaiHang mountain. All of this providing the premise for the application of terrain model in practice.