Space Research Organization EAEQG Subdivision Grid Model-based Approach

Traditional planar data model is that3D spatial data into two-dimensional Euclidean spatial data based on geographic coordinates by means of map projection.In large regional and global scales,projection transformation approach inevitably determines spatial data fragmentation, overlapping and geometric deformation phenomenon of spatial entities.Thus, the traditional planar data model is difficult to achieve large area and mass data quickly and efficiently expression storage, and management.meanwhile, along with the increasingly rich earth observation method, the spatial information of dynamic monitoring area has expanded from local to global.Spatial data is becoming a multi-disciplinary and multi-field research data base.Therefore, how to quickly and efficiently store, express and manage the global multi-scale spatial data, has become one of the important problem of spatial information science research.Based on the theory of global discrete grid model framework of spatial information organization is considered to be the traditional plane grid model in dealing with a large regional or global geographical spatial data of many problems in the most effective way. Because of a shortage of current subdivision model there are the following:1. Adaptive mesh model is a single level or a single scale of irregular profile control subsystem, unfavorable to the boundary of dynamic operations, and lack of the level of the data expression, it is difficult to directly contact with scale or spatial resolution, it is difficult to solve the spherical multi-level comprehensive massive data processing and spatial analysis;2. Regular polyhedron grid model due to involve complex projection operation, leading to a lower operation efficiency, difficult to guarantee the efficient conversion data. At the same time of existing data integration and inheritance;3. The latitude and longitude grid model level subdivision unit many defects such as deformation is large, difficult to adapt to the modern information technology, increasingly diverse application requirements.Therefore, this article summarizes the existing global discrete Grid model advantages and disadvantages, on the basis of innovative put forward the new Grid subdivision model--such as Area of ellipsoid Quadtree Grid EAEQG (Equal-Area Ellipsoidal Quadtree Grid) model.EAEQG grid model is a kind of seamless, no fold covering global subdivision grid, to ensure the same level of subdivision unit area is equal, and with the same geometry and topology.Realize the fast transformation subdivision units and geographical coordinates, at the same time support multiresolution expression of spatial data.EAEQG subdivision model exactly is, choose latitude and longitude subdivision model good inherited the latitude and longitude subdivision model easy to split unit between encoding and geographical coordinates transform and inherited the advantages of good of historical data. In avoiding the latitude and longitude grid subdivision model can cause the same cutting layer under subdivision unit deformation problem, this paper will adopt degradation quadtree partitioning method, control subdivision unit deformation increases with the increase of latitude at the same level.Calculated at the same time, in order to simplify the subdivision of the complexity of the algorithm, the idea is polyhedral subdivision EAEQG grid subdivision.Will is specific to the WGS-84ellipsoid octahedron, initialize subdivision.The rotating ellipsoid average cutting into8geometry and characteristics completely equal eight fission.Thus will global subdivision calculation and operation algorithm, calculation and simplify the eighth to the body of subdivision algorithm, thus greatly improving the operation and computing speed, the running efficiency of system.Using quadtree partitioning, determines the subdivision of EAEQG subdivision aperture is4, at the same time, also easy to use binary Morton code, improve the coding efficiency and subdivision code rate and mutual transformation between the geographic coordinates.EAEQG subdivision basic subdivision unit basic geometric structure adopted rules of ellipsoid quadrilateral, abandoned the rules such as triangle, hexagon, lozenge geometric structure, thereby avoiding the subdivision of regular polyhedron subdivision unit in the projection mapping to the spherical geometry deformation, maximum limit guaranteed the geometric stability of each subdivision unit, and avoids the triangle, hexagon, diamond and other rules difficult to geometric subdivision unit with geographic coordinates conversion problem.At the same time, the simple quadrilateral topological relationship make it easier to realize spatial data search and logical judgment.EAEQG grid subdivision model, in the process of decomposition, deliberately keep each subdivision unit area such as geometric features.This feature makes EAEQG profile control points according to the subdivision calculation and statistical query has unmatched advantages. In accordance with the unified global spatial information organization of ideas, design a new framework-based on spatial information subdivision organization EAEQG grid spatial information subdivision organization framework.And the principle of EAEQG grid subdivision, node coordinates calculation method, coding method of subdivision units, grid coding with geographic coordinates transformation algorithm, adjacent search method, geometric characteristics analysis, spatial information subdivision of the identification principle and design scheme of prototype system, etc, are discussed in detail.This paper innovation points as follows:(1) the WGS-84coordinate system, as a spatial reference benchmark.In WGS-84ellipsoid direct subdivision, good well meet the requirements of modern spatial information processing for high precision.(2) put forward the new grid subdivision model EAEQG grid model, it is impossible to make up for some deficiencies of existing global discrete grid model.