Research On True Three-Dimensional Geospatial Computing Method For Large Area Based On SGOG Bricks

The earth system is a fluid space with multi-circle layers in physics and a complex and non-linear giant system in logic.The data model of people's understanding and description of geospatial has gone through three stages: map projection,Discrete Global Grid Systems(DGGs)and Earth System Spatial Grid(ESSG).Map projection model for small-scale space has three major problems: data cracks,inaccurate spatial analysis,and difficulty in data integration and sharing.DGGs only restored the fluid properties of the earth's surface,and still belonged to the projection model in essence(the projection surface is spherical).ESSG,a basis of building a new generation of true three-dimensional digital earth platform,has completely restored the fluid nature of the Earth's system space and is oriented to the integration of large spatial and temporal data.So it is of great significance to study global or regional comprehensive problems.Sphere Geodesic Octree Grid(SGOG)is a kind of ESSG model,which has the characteristics of concise division rules,simple tile shape,regular arrangement and clear geometric characteristics.Previous research has achieved the basic model theory of partition system construction,grid deformation analysis,grid coding and decoding methods.On the basis of the above,this paper realizes the application of SGOG grid in the true three-dimensional modeling and analysis of terrain and geological body in large watershed.The main research results are as follows:(1)A modified SGOG coding method is proposed.For the existing SGOG grid coding mainly for the defects of the earth solid itself,the layer code part is represented by a hexadecimal number.Distinguish between spherical quadtree splitting and radial binary tree splitting to achieve horizontal and radial independent splitting.In order to solve the problem that the fixed direction coding code sequence is different,which is not conducive to the model rendering,a modified direction coding method is proposed.(2)A large-scale geospatial three-dimensional modeling method based on SGOG bricks is proposed.According to the SGOG's splitting mechanism,the geospatial feature points that have been processed(sparse or encrypted)are mapped to a certain layer of grid coding,and then implemented on the brick entity to construct a multi-scale geospatial visualization model.Using the threshold of geospatial features(elevation or stratigraphic properties,etc.),control the recursive splitting hierarchy of SGOG,and construct an adaptive multi-scale geospatial true three-dimensional model.Based on SGOG bricks,true three-dimensional modeling of sky,air and ground integration can be realized.(3)The method of true three-dimensional geospatial analysis is studied.Based on the true three-dimensional geomorphic model of the Yangtze River Basin and the geometric characteristics of SGOG bricks,the multi-scale true three-dimensional terrain parameters were extracted and analyzed.Including the real surface area of the basin,the projected area of the spherical surface,the relief of the terrain,the roughness of the surface,the two-dimensional and three-dimensional fractal dimension of the watershed,and compared with the corresponding parameters of the projected grid model.Based on the stratigraphic SGOG grid model of the Zhengzhou Airport Economic Zone,a true three-dimensional analysis of the underground space is realized.Includes geometric features(surface area and volume)calculations,arbitrary 3D profiles,and virtual digital drilling.(4)A true 3D geospatial modeling and analysis system based on SGOG bricks was developed.Based on the above research,using the MFC framework and the OSG environment,the development of a true 3D geospatial modeling and analysis system based on SGOG bricks is realized.Functions include SGOG split algorithm implementation,large-scale geospatial true 3D modeling and rendering,digital terrain analysis,and underground space 3D analysis.Obtained 2 software copyrights.