Research Of Contour Line Generation And Color Fill Based On Triangulation

With the rapid development of GIS (Geographic Information System) technologies and its applications, the speed for producing DEM is required to be improved continuously. This thesis focuses on the area of producing DEM (Digital Elevation Model), researchs mainly on the Algorithm of Delaunay Triangulation for the scattered points, the algorithm of extraction and disposing contours based on TIN, as well as the color fill between contour lines.At the aspect of the algorithm of Delaunay Triangulation In incremental insertation algorithm, it organizes the point set and triangle by constructing Grid index to enhance the query speed of searching for the triangle that contains the given point. With the improving measures, the efficiency of algorithm is greatly improved.At the aspect of the algorithm of extraction and disposing contours based on TIN, coumputed the coordinate of equivalent points according to using interpolating method if there were equivalent points in each edge of triangles.Tracing and drawing equivalent point created ioslines.Deal with the problem of smoothing contours by using Tension Spline Function.At the aspent of color fill between contour lines, enstablish the topology with the coutour lines, form the closed area and the no-closed area, and finally fill the region by different color according to the elevation value according to the surrounded contour lines.