Geovisualization Of True3D Watershed Geo Scenedrivenon Earth Tessellation Grid

Earth System Spatial Grid(ESSG)is a multi-resolution discrete earth reference model formed by recursive subdivision of the whole earth space.It completely restores the fluid properties of the earth,eliminates the projection deformation,and is the model primitive of constructing the digital earth.At present,ESSG research is more common in grid subdivision,spatial index,grid deformation and visual modeling,and there are few studies on vector data grid expression and real three-dimensional modeling of large-scale watershed geographic scenes.In view of the above problems,In view of the above problems,this paper takes the construction of true three-dimensional geographic scene of river basin as the goal,and takes Sphere Geodesic Octree Grid(SGOG)as the modeling element,on the basis of in-depth analysis of the topological relationship of the grid,this paper studies the conversion method of spatial vector data and grid data,designs the integrated management data structure of heterogeneous vector data based on spherical grid,and puts forward the vector grid integrated expression optimization method of grid true three-dimensional model,which has achieved good results.The main work and contributions of this paper are as follows:1.According to the basic theory of grid subdivision,two proximity search algorithms for QTM grid were proposed.Based on the SGOG grid subdivision and coding scheme,the three-dimensional coordinate system of spherical triangulation was introduced to express the topological relationship of SGOG grid.The roaming path problem of SGOG spherical grid was solved by grid combination,and the universal proximity search algorithm of QTM grid based on three-dimensional coordinate was proposed.At the same time,the proximity search algorithm of SGOG spherical QTM grid was proposed according to the characteristics of SGOG coding,and the above two algorithms were experimentally compared.The experimental results show that although the nearest neighbor search algorithm based on three-dimensional coordinates has efficiency advantage in continuous nearest neighbor search,and the nearest neighbor search algorithm based on SGOG coding has efficiency advantage in calculating single nearest neighbor search.2.Based on SGOG grid topology and near search algorithm,a gridding method of spatial lines,surfaces and volumes was proposed.For the gridding problem of line elements,the equivalence relationship between the vector line grid expression problem in space and the optimal roaming path problem in space was revealed,so as to realize the dimension reduction algorithm of vector line SGOG spherical grid expression;On this basis,considering the topological relationship of SGOG grid and adjacent search,the QTM grid expression algorithm of surface elements and the SGOG sphere grid expression algorithm of B-rep elements were realized.The experimental verifications show that: the grid algorithm of the above three basic elements can generate the grid model results with good overall effect and high fitting accuracy,which has practical application value and provides strong technical support for the next three-dimensional scene model construction research.3.According to the characteristics of sphere grid,a method of integrated management of ground and underground geospatial data based on SGOG grid and integrated modeling of true three-dimensional vector grid was proposed.A unified and object-oriented SGOG data structure scheme was designed for heterogeneous geospatial data;Aiming at the shortcomings of the grid model in visualization,the modeling and analysis method of true three-dimensional vector-grid integration driven by spherical grid data model was proposed and implemented.The advantages of vector and grid data models are fully utilized,and has achieved good visualization results.4.A spherical grid-driven true 3D geographic scene modeling and analysis system was developed.Based on the above research,a real three-dimensional geographic scene modeling and analysis system driven by sphere grid was developed.The system takes VS2017 as the development platform,Qt as the system framework,OSG as the three-dimensional rendering engine,My SQL as the underlying database,and uses standard C++ 11 language to develop.It mainly includes two functional modules: real three-dimensional modeling visualization and spatial object statistics and analysis.This system has obtained four software copyrights of the State Intellectual Property Office.This system has obtained four software copyrights of the State Intellectual Property Office.