基于栅格DEM的地形特征提取与分析

以陕北延安地区燕儿沟流域为实验样区,运用比较分析法和数理统计法进行基于栅格DEM的地形特征提取和分析,以及DEM分辨率对地形特征的影响,并计算和比较了地形特征的空间统计分布。研究表明:一个相对真实的DEM能够通过修改生成DEM的基本材料,以及对DEM进行再加工而获得。由于DEM分辨率的不同,由此得到的地形特征值(如坡度、地形指数、河网密度等)在统计特性上也会随之变化。随着DEM分辨率的降低,坡度减小,地形坦化,地形指数均值变大,流域总面积变大,子流域数量减少,河流总长度减小,河网密度降低。

Topographic attributes extraction and analysis based on grid DEM

Taking Yan'er Gully watershed as a test area and ArcGIS as a test tool,extraction and analysis of topographic attributes based on grid DEMs are discussed in this paper.The spatial and statistical distribution of topographic attributes are computed and compared.It is assumed that a relative real DEM which is consistent with natural land surface can be produced through reconditioning basic material generated DEM and reprocessing DEM.Methodology of Mathematic statistics and comparative analysis are used to analyze effect of DEMs with different grid resolutions on the outcome of topographic terrain extraction,including slope,topographic index(i.e.ln(α/tan β)),watershed and subwatershed area,and drainage network.Analysis results of topographic attributes derived form different grid resolution DEMs indicates that with the decrease of DEM resolution,terrain is smoothing,the mean value of slope decreases,the mean value of ln(α/tanβ) distribution increases,the total area of the watershed increases,the count of subwatersheds decrease,the total length of streams decrease,and the drainage density decreases.