基于DEM的陕北黄土高原地形因子的提取与分析

Extract and analysis topographic factors of Loess Plateau in northern Shaanxi based on DEM

本文基于SRTM(90 m)DEM数据,提取陕北黄土高原多个地形因子。通过ArcGIS中盆域分析及分水岭工具,结合ETM影像特点,将整个研究区划分成11个区域,对各区域内部的各类地形因子进行定量分析,揭示陕北黄土高原地貌形态的空间变化情况。结果显示:高程、坡度、坡向等由DEM直接获取地形因子的精度与DEM本身精度相关,坡度变率、坡向变率、地形起伏度及高程变异系数等表征地形变化量的地形因子在数值上整体呈现正项分布趋势。高程均值在1000~1600 m之间,研究区3、8、10、11的内部高差大于1000 m,其余研究内部高差小于1000 m;坡度变率与坡度值分布情况一致,研究区1、4属于值较小的一组,研究区2、3、5属于第二组;各研究区坡向分布均匀,坡向众数出现最多的为西南向和东向。所有研究区水平曲率高于0的面积最大,低于0次之,等于0的最小;研究区2及研究区10剖面曲率0以上的面积占比大于0以下的面积占比,其余研究区相反,所有研究区剖面曲率等于0的面积占比最小;在本文的窗口尺寸下,地形起伏度、高程变异系数的值随提取窗口的增大而增大,研究区1和4的地形起伏度RF和高程变异系数V值均明显小于其他研究区,其余研究区地形起伏度RF及高程变异系数V值随位置和窗口的变化而波动变化。

Based on SRTM(90 m)DEM data,this paper extracts multiple topographic factors from the Loess Plateau in northern Shaanxi.Through ArcGIS basin domain analysis and watershed tool combined with ETM image characteristics,the whole research area is divided into 11 regions,and the various topographical factors within each region are quantitatively analyzed to reveal the spatial changes of the geomorphological morphology of the loess plateau in northern Shaanxi Province.The results show that:Elevation,slope,aspect,etc.directly obtained by the DEM topographic factor accuracy is related to the accuracy of the DEM itself.Terrain factors that characterize the amount of terrain change,such as slope variability,aspect variability,topographic relief and elevation coefficient of variation,tend to positive distribution in values.the mean of the elevation is between 1000 m and 1600 m,the internal height difference of the research area 3,8,10,11 is greater than 1000 m,and the rest of the study is less than 1000 m.The distribution of slope variation rate is similar to distribution of slope values.Study areas 1,4 belong to a group with a smaller value,and study areas 2,3,and 5 belong to the second group.The slope distribution in each study area is uniform,and the largest number of sloped populations appears in the southwest and eastbound direction.In all study areas,the area of plane curvature above 0 is the largest,below 0 is smaller,and equal to 0 is the smallest.In the study areas 2 and 10,the area ratio of the profile curvature above 0 is greater than the proportion of area below 0,while the remaining study areas is opposite.The area of all study areas with a curvature equal to 0 is the smallest.Under the window size of this paper,the value of relief amplitude and elevation variation coefficient increases with the increase of the extraction window.The topographic relief and elevation coefficient of variation of study areas 1 and 4 are significantly smaller than other study areas.The rest of the study area topographic relief and elevation coefficient of variation value fluctuate with position and window changes.