格网DEM坡度计算模型的相似性研究

Similarity assessment on slope models used in grid-based DEM

当DEM的精度和分辨率确定后,坡度坡向计算结果取决于计算模型。本文设计了逐栅格单元的相对差等级评价方法,并结合基于整体的频率图和XY散点图评价指标,定量揭示了坡度计算模型之间的异同。主要结论为:①坡度计算模型有离散和连续之分,连续型模型能给出更加符合实际的坡度坡向计算结果;②坡度计算结果与计算点数有关,点数越多,计算结果越稳定;③算法间的差异随DEM分辨率的增大而增大。最后本文给出了实际应用中的坡度计算模型。

If accuracy and horizontal resolution of DEM is set, accuracy of slope and aspect is depend on the algorithm that used to derive them. In the paper, a slope model evaluating method called relative differences which is calculated cell by cell is put forward. Based on the relative differences, frequency distribution map and the XY scatter diagram, the similarities and differences of the selected slope algorithms are discovered quantitatively. The main conclusions are： ①present slope algorithms are classified into the discrete and the continuous, in which results of the continuous ones can be more accurate according to the true value ; ②the accuracy of slope depends on the number of grid points that used. That is to say, the more the number of grid point, the more stable the result;③ the differences among algorithms enlarge as the DEM resolution increases. Finally the slope algorithms and their applicable conditions are discussed.