QTM地址码与经纬度坐标的快速转换算法

Fast Translating Algorithm between QTM Code and Longitude/Latitude Coordination

球面四元三角网(QTM———QuarternaryTriangularMesh)结构是目前研究全球海量数据管理的有效方法之一。但是,在现有的QTM地址码与经纬度的转换算法中,"ZOT投影法"的转换速度快,但生成的编码缺乏方向性;"ETP投影法"生成的编码具有固定的方向性,但转换速度慢。为解决这个矛盾,提出一个新的转换算法———"行列逼近法"(CAM———CavalcadeApproachMethod),其算法的基本原理是根据QTM的行和列,按一定的方向递归逼近地址码。文章给出了算法的详细步骤,并在实验中应用不同点数在不同层次对几种典型的转换算法进行了对比分析,结果表明:"行列逼近法"在保证所生成的地址码具有固定方向性的同时,时间消耗仅为"等三角投影法"的7%～20%左右。

QTM (Quarternary Triangular Mesh) structure on spherical surface is an efficient method in managing the global large quantities of the earth data. But the existed translating methods between QTM Code and Longitude/Latitude Coordination have low efficiency in translating speed or lack of certain orientation in encoding. To overcome this serious deficiency, a new translation method——CAM (Cavalcade Approach Method) is presented. The principle of this method is based on the Row and Column of QTM and recursively approach the address codes according to certain orientation. Detailed steps of new algorithm are also presented. Different translating methods are analyzed in experiment by using different number of points in different levels. The result indicates that in CAM method not only the address code is generated in certain orientation but also time consumption is only about 7%～20% of ETP (EqualTriangles Projection) method.