The Study Of Spherical Quad-tree Subdivision Model Under Natural Coding

Global discrete grid is a kind of qualified nets that based on the sphere which can be infinitely subdivided, but do not change its shape. Using global discrete grid model to represent spherical map, not only can overcome the defects that produced by map projection and map framing but also can meet the needs of management and organization of massive spatial data. With the progress and development of science and technology, more and more areas need Global spatial information. The research of discrete global grid is imperative, and currently Discrete global grid is one of the hot research field of Geo-science in home and abroad and other related disciplines.This paper studies several common global discrete grid models, by analyzing and comparing the advantages and disadvantages of each spherical subdivision model, selected the presently most advantageous of spherical subdivision model that is global authalic quad-tree grid model. At the process of the exploration of global authalic quad-tree grid model’s usability, we find its original coding system exists deficient in some respects. Through the research and analysis of several mature global discrete grid coding systems, we find the linear quad-tree coding method of natural number is a good solution to these deficiencies. Through studying the principles and methods of linear quad-tree coding’s, this paper proposes a new coding system and uses quaternary Morton code to represent the address grid unit in the calculation. This paper also studies the conversion of latitude and longitude coordinates and grid address code under this new coding system, and gives the algorithms of mutual conversion. Finally this paper analyzes the deformation of global authalic quad-tree grid model, QTM model and DQG model.