Research On Rapid And High-precision DEM Producing Technique

With the rapid development of 3S(GIS,RS,GPS) technologies and their applications,the precision of DEM and its producing speed are required to be improved continuously. This thesis focuses on the area of producing high-precision DEM rapidly,trying to find the solution to this urgent and significant problem. The author puts emphases on its bottleneck,producing algorithm,and related spatial data structure. And a series of initiations and fruits are realized.1.This thesis proposes an algorithm flow of rapid and high-precision DEM producing:construction of ordinary TIN,limitation of contour lines,optimization of TIN,processing of flat triangles,and edge embedding of work areas. This flow can sufficiently reflect the characteristics of real terrain and its contour lines.2.This thesis initiatively proposes the producing algorithm of ordinary TIN,based on the Convex Hull Technique. Through real practice and theoretical analysis,the time complexity of this algorithm is close to O(n),so we had solved the bottleneck problem in DEM producing.3.This thesis constructs the topological data structure to efficiently materialize some algorithms,such as construction of ordinary TIN,limitation of contour lines,optimization of TIN,processing of flat triangles and edge embedding of work areas,based on points,lines,and areas(triangles). 4.This thesis initiatively proposes the rapid-location algorithm based on the Scan-Line Technique,making full use of the topological data structure of DEM. This algorithm improves the edge-embedding efficiency. At the same time,this algorithm materializes not only the rapid location in DEM,but also the rapid belonging judgment of inner-points and isolated islands. 5.This thesis materializes the united processing for the error-checking function in digitalization of relief maps information and DEM producing. In other words,the error-checking mechanism,considering the topological relation,isembedded in the process of producing DEM.This progress provides automatic error-checking method for high-quality terrain data acquisition,and greatly improves the efficiency of digitalization for relief maps.6.This thesis solves the rapid DEM producing problem for large-scale terrain "massive data". At the same time,it implements robustness processing on each significant algorithm,which avoids the potential failure in DEM producing due to the mathematical computing errors.7.This thesis provides complete demonstration for the Diagonal Exchanging Algorithm,in the process of contour-line limitation,which offers the theoretical foundation for the application of the Diagonal Exchanging Algorithm in high-precision DEM producing.8.This thesis initiates the 8-Quadrant Angle Computing Method. This method can rapidly recognize the adjacency relationship of all the edges linked with the same node and avoid the complicated computing of trigonometric function. Furthermore,this method can rapidly construct the adjacency relationship of all the arcs linked with the same node,in the construction of topological data structure in GIS,which is helpful to the rapid construction of topological structure. The DEM producing algorithm proposed in this thesis can meet the goal ofrapid and high-precision DEM producing,as the practices of our DEM analysissystem in several research projects indicate.