Dem Surface Topography Mutations Characteristic Expression Method

In respect of topographical representation, both the traditional geography and GIS science consider the earth's surface as a continuous field consisting of elevation changes, while neglect certain local peak and sink. Hence they generate DEM with smoother surface. However, as a matter of fact, the earth's surface is not as continuous or smooth as a field. Breaklines, such as cliffs, gully edges, ect, exist by natural or artificial agencies, and undoubtedly influence material and energy transfer such as the sediment and the runoff on the surface. During the process of constructing DEM, the important topics are how to embed the breaklines information on DEM surface, how to represent on characteristics of discontinuous terrain, and how to increase the integrity while decrease the corresponding uncertainty of topographical representation. On the basis of the field digital surveying and the data abstraction from topographic map, this research brings both artificial and natural reaklines into interpolation operation in order to explore the practical and simple representation on discontinuous terrain based on the "smooth" DEM. The research contents mainly include:(1) The representation on characteristics of mutational terrain. On the data basis of geographic data and topographic maps of 1:10000 and 1:50000, it is constructed twelve series of DEMs with multiple resolutions (0.5,1,2.5,5,10m) via the application of Hutchinson and TIN methods.(2) Analysis on elevation of DEMs. A comparative analysis on multiple series of DEMs including mutational cliffs or not is conducted via an application of hypsometric integral analysis, frequency analysis, statistic analysis, and information entropy calculation, etc.(3) Analysis on slope and curvature of DEMs. A comparative analysis on DEMs including mutational cliffs or not is conducted via an application of frequency analysis on slope, on curvature, and on the difference value of slope, statistic analysis, and information entropy calculation, etc.It is concluded that the simple and practical method of the representation for artificial discontinuous terrain on the DEM surface is to construct hydrologically correct DEM (Hc-DEM) with resolution of lm via an application of Hutchinson method, based on the data of contour lines, spot heights, and breaklines(terrace). Here, contour lines with intervals of 0.5m or 1m are the best choice of data basis, and the essential requirement is that no abnormally protruding points or lines emerge in DEM with the addition of breaklines.