Study On Update Method Of DEM Data Based On Delaunay Triangulation Irregular Network

DEM(digital elevation model)simulates the terrain surface in numerical elevation matrix.As an essential part of national spatial data infrastructure,DEM is widely applied to 3D Terrain Visualization,image processing,urban planning,road design,etc.Currently,With the fast development of modern urban construction,road design and planning department urgently need to update the existing DEM data.However,the existing DEM update methods cost a long update period,which is not enough to meet the demand of realistic production and construction.In order to change this situation,the update method based on Delaunay Triangulation Irregular Network(D-TIN)dynamic updating technology is proposed for the first time to realize update on locally DEM data.Specific research contents and results are as follows:(1)The points from Grid DEM data are extracted by preserving important points method in order to use the least points to the maximum keep terrain features and improve the D-TIN construction speed.(2)D-TIN is constructed with synthetic algorithm of convex hull and point-by-point insertion,based on the linear plus or minus sex construct convex hull and improve the efficiency of point by point insertion algorithm by using the data structure of generalized map with topological characteristics.The results show that the constructed D-TIN meets the properties of Delaunay,and this D-TIN-building algorithm is proved to be simpler and more efficient.(3)Road lines are inserted to the constructed D-TIN by G-map data structure with loop back algorithm,the D-TIN data located within the road lines are deleted with the algorithm of lug combining empty circum-circle detection.D-TIN has completed update based on road elevation data,and it's effectiveness has been verified by using the three-dimensional road update experiments.(4)Convert the updated D-TIN to grid DEM data with linear interpolation algorithm.The areas within the converted road lines exist sinked and raised phenomena which is solved by extending certain distances.The optimal extended distance is ensured by observing the experimental pictures of road updating as well as analysizing experimental data of wrong areas proportion within road lines and increased areas proportion outside road lines.Finally realize the goal of DEM data update effectively.(5)Based on the Visual Studio 2010 development environment,using C++development language,Gdal development kit,OpenGL graphics apis,simulate the system of DEM data updating based on D-TIN.The characteristics of the paper are not only proposing the DEM data updating method based on D-TIN dynamic updating technology,but also improving the speed of the algorithm of D-TIN constructing and D-TIN updating by using G-map data structure with topological characteristics.This research solves cycle problem of the traditional DEM data updating.At the same time,this DEM data updating system can provide outstanding technical support for road planning and design departments.