DEM分辨率对坡度算法选择影响的分析

DEM Resolution Influence on Slope Algorithm Selection

坡度是重要的地表形态要素,DEM的分辨率对坡度计算具有十分重要影响。研究DEM分辨率对坡度最优算法选择的影响,对坡度精度评价具有重要意义。本文选取地形复杂的绥德和地形简单的拜泉两个样区,生成10~200m一系列分辨率的DEM,通过对比坡度计算的误差、坡度的信息熵和坡度衰减,分析Horn(H)算法、Zevenbergen(Z)算法、Evans-Young(EY)算法、Sobel(Sb)算法和Sharpnack(Sp)算法这五种坡度算法随DEM分辨率变化的表现,认识理解分辨率对坡度算法选择的影响。结果表明:(1)根据误差结果,各种分辨率下EY算法均为最优;根据信息熵和坡度衰减(平均值、标准差)结果,各种分辨率下H算法均为最优;(2)DEM分辨率对算法的影响主要表现在其坡度计算结果的差异程度上。在高分辨率时,不同算法得到的坡度结果差异不大;而在低分辨率时坡度结果的差异很大,宜使用推荐的算法;(3)随DEM分辨率降低,五种算法得到的坡度均发生衰减,但衰减程度不同,其中H算法衰减最小。(4)在实际坡度计算时,若重点关注坡度的精度,则优先考虑选用EY算法;若重点关注低分辨率情形下坡度的衰减,则优先考虑选用H算法。研究结果对不同分辨率下坡度算法选择和坡度精度评价均具有十分重要的意义,这还为地学模型提供了更精确的坡度数据。

The DEM-based calculation of slope,as an essential terrain variable,is affected by DEM resolution.The influence of DEM resolution on optimal slope algorithm should be studied to improve the slope calculation accuracy.In this paper,two study areas Suide with complex terrain and Baiquan with simple terrain in China were selected to generate a series of DEMs with resolutions ranging from 10 m to 200 m.Then,the slope calculation error,the slope entropy,and slope attenuation of five slope algorithms,including the Horn(H),the Zevenbergen(Z),the Evans-Young(EY),the Sobel(Sb),and the Sharpnack(Sp)algorithms were compared with DEM resolutions to understand the resolution influence on slope algorithm selection.The results obtained:(1)In each case according to the error results,the EY algorithm was the best choice in each resolution.In contrast,according to entropy and the mean and standard deviations of slope attenuation results,the H algorithm was the best choice in each resolution.(2)The DEM resolution influence on the algorithm could be mainly reflected in different slope difference results.The slope results obtained by different algorithms for high resolutions were not entirely different,while those calculated for low resolutions were quite different.Thus,the optimal algorithm should be utilized in low-resolution cases.(3)As DEM resolution became coarser,the slope results calculated by these five algorithms attenuated.However,different degrees of slope attenuation could be obtained with different algorithms,while the minimum attenuation was obtained with the H algorithm.(4)In practical slope calculation,the EY algorithm was preferred if the slope calculation accuracy was focused,while the H algorithm could be utilized if the slope reduction was considered in low-resolution DEM-based calculation.The research results were of great significance for slope algorithm selection at different resolutions and slope accuracy evaluation under different resolutions.Moreover,they provided more accurate slope data for geoscience models.