DEM结构特征对坡度坡向的影响分析

Research on Error of Derived Slope and Aspect Related to DEM Data Properties

数字高程模型已严格定义为按规则格网阵列记录的地形高程数据,其固有的结构特征(如格网分辨率、格网方向、高程数据准确度等)直接影响DEM对地形表达和坡度、坡向的计算精度。该文通过理论和数据独立的DEM实验分析方法,研究了DEM结构特征对坡度、坡向的影响,得出如下结论:1)高分辨率的DEM并不一定能给出高精度的坡度、坡向计算结果;2)可通过g=bm/ms×180/π×cos2S来选择合适的DEM分辨率;3)三阶不带权差分算法的坡度、坡向计算结果对DEM方向有较强的依赖性。

Today digital elevation data have been commonly provided in grid data structure,so that the term DEM has been widely regarded as digital elevation grid.The DEM data properties such as resolution,orientation and data precision have effect on slope and aspect derived from DEM.This paper studies the relationship between DEM data properties and slope and aspect by theories and data-independent DEM error analysis.The findings of this study can be summarized as:1)High resolution DEM does not assure high accuracy of slope and aspect.2)Appropriate DEM resolution(g)may be expressed by RMSE of DEM(m),RMSE of slope(mS)and DEM mean slope(S),g=bm/ms×180/π×cos2 S,in which b is coefficient of data error of slope algorithms.3) Grid orientation does cause directional bias on derived slope and aspect,and the third-order finite difference algorithm series,which encompass 3rd order finite difference,3rd order finite difference weighted by reciprocal of squared distance and 3rd order finite difference weighted by reciprocal of distance,have shown the most significant errors due to the change of grid orientation.