A global and local coding mapping method based on DQG-3D grid

  Objectives  : With the increase of exploration and production activities of earth science,the demand for space data management is also developing from the surface to the three-dimensional dimension of underground,air and space.The global discrete grid is a new generation of integrated space data model integrating space and earth Space geographic entities on earth distribution scale differences,both global macro scope and local micro scope,the research range scale size,mesh,accuracy requirements,and data processing capacity,the influence of such factors as local micro range using local grid computing is more advantage,but not lost the unity of global grid.Therefore,a global and local unified three-dimensional grid framework is designed and the mapping method between local grid and global grid code is implemented to provide a basis for global and local three-dimensional spatial information management.   Methods  : Firstly,based on the spherical DQG grid partitioning method,the three-dimensional extension is carried out.The sphere is still divided by degraded quadtree,and the binary tree is divided radially to form DQG-3D grid,The DQG-3D grid cells are encoded using Z-curve coding,which consists of octet coding and 3D Morton code.Then,in the framework of global DQG-3D grid,the identification level of the global grid is determined by comparing the area of the outer square of the study area with the area of the spherical DQG grid.At the level of identification,the local basic grid is determined,and the local basic grid is divided and coded by octree.Finally,the mapping between local grid and global grid code is realized.For non-degenerate regions,grid code bit operation is used for direct mapping.For degenerate regions,local row number,column number and layer number are used to calculate global row number,column number and layer number.   Results  : Experimental results show that in a grid and non-degenerate region,the efficiency of the proposed algorithm is 30 times and 11 times higher than that of the traditional method based on longitude,latitude and altitude.The modeling efficiency of local grid is 13 times that of global grid.   Conclusions  : The proposed method can meet the requirements of efficient expression and application of global unified model and local refined model.Further research will be based on binary coding operations and spatial analysis of local and global grid coding.