A Three-Dimensional Buffer Generation Method Based On The Sphere QTM Octree Grid

The Discrete Global Grid System(DGGS)is a geospatial data expression and analysis model based on the infinite subdivision of the earth’s sphere(body)to simulate the earth.The research on the subdivision modeling and coding scheme of the Discrete Spherical Grid System has been relatively and achieved very fruitful results,while the research on Earth System Spatial Grid(ESSG)needs to be improved.However,most of the research on ESSG is limited to the field of subdivision modeling and spatial visualization,and there are few studies on 3D geospatial computing.As far as buffer construction is concerned,the traditional 3D vector and grid buffer generation algorithms are very mature,but there are few reports on the 3D buffer generation algorithm based on the DGGS.Aiming at this situation,this paper focuses on the problems related to buffer generation based on DGGS.The main work and content of the paper are as follows:1.Based on the existing three orientation geographic grid coordinate system,establish a three orientation symmetrical grid coordinate system.In this paper,the characteristics of the three orientation symmetrical grid coordinate system are analyzed in depth.For the application of spatial symmetry distance calculation,the three coordinate origins are integrated into one,and moved to the center of the spherical triangle uniformly,and the coordinate values are recorded according to the natural distribution of the grid,and a three orientation symmetrical grid coordinate system is established.On the basis of the above,the conversion algorithm of three-way symmetrical coordinates and QTM(Quaternary Triangular Mesh)fixed-direction encoding is designed and implemented,which provides key theoretical support for the design of the grid neighborhood expansion algorithm in the following.2.A 2D buffer generation method based on DGGS is proposed.The spatial symmetry of the QTM grid is mapped to the encoding of three orientation symmetrical grid coordinates,and the buffer is regarded as the neighborhood expansion of the central cell,and the cell neighborhood expansion algorithm of QTM is designed accordingly.And based on this,considering the spatial adjacency relationship of various entity expansion areas,based on the QTM grid,the generation of two-dimensional buffers of point,line and area objects is realized.Extending the above method to other types of grids,a symmetric grid coordinate system is proposed for rhombic and hexagonal grids.Based on this,the adjacent symmetrical distance analysis of the grid element is carried out,and the generation of the two-dimensional buffer corresponding to the grid is realized,which verifies the effectiveness and universality of the algorithm.3.A 3D buffer generation method based on Sphere Geodesic Octree Grid(SGOG)is proposed.The 3D buffer is reduced in dimension,and the 3D buffer is regarded as the radial neighborhood expansion of the 2D buffer cell.In this way,an SGOG voxel radial neighborhood expansion algorithm is proposed,which realizes the generation of3D buffers for point,line and volume objects.The experimental results and theoretical analysis show that the complexity of this algorithm is O(R~2),which is better than that of the traditional grid algorithm O(R~3).Finally,a spatial relationship query algorithm for SGOG grid is proposed,which provides the basis for the buffer query analysis.4.A 3D Buffer Generation System Based on Spherical Space Discrete Grid has been development.Based on the above research,a 3D buffer generation system based on discrete grids in spherical space was development.The system takes VS2017 as the development platform,Qt as the system framework,OSG as the three-dimensional rendering engine,SQL Server as the underlying database,and uses standard C++11language to develop.It mainly includes two basic modules:3D buffer generation modeling and spatial relationship query.