黄土高原坡向信息量变化与DEM分辨率的关系

The relationship between the resolution of DEM and the accuracy of aspects and the amount of information losses in Loess Plateau

运用非线性回归方法,研究了从数字高程模型(DEM)所提取坡向信息量随 DEM分辨率变化而变化的函数规律。在中国西北部黄土高原选取了代表7种黄土地貌类型的252个样区。在每个样区以1:10000地形图为数据源建立了分辨率分别为5,15,25,…,75m 的 DEM。以5m 分辨率 DEM 提取的坡向信息为假定真实值,以其它分辨率 DEM 提取的坡向信息为研究对象,分析了坡向信息量的损失与分辨率的函数关系。提出了基于单个栅格的坡向分类别正确率(a)指标和坡向信息量损失(q)指标。在每一类地貌类型区得到了上述两项误差指标与分辨率的函数关系,可以根据函数关系由已知误差求得所需要的分辨率。函数关系的建立可在保证预定坡向信息的精度前提下,选定 DEM 的适宜分辨率,减小数据量,降低成本。

The variations of the amount of aspect information derived from a digital elevation model （DEM） with the DEM＇ resolution were studied using the non-linear regression method. In the northwest China＇ s Loess Plateau, seven major sample areas representing different landforms were selected, each of which was divided into 16 subareas. The DEMs with the resolutions of 5m, 15m, 25m, 35m, 45m, 55m, 65m, 75m, respectively, were established according to the map scaled at 1 ： 10000 on each sample area. The aspect information derived from the DEM with the resolution of 5m was assumed as the true value, and the information derived from other DEMs was taken as the investigated subject. The functional relations between aspect information losses and resolutions were analyzed. The indexes of the aspect accuracy （ a ） of different categories and the information loss （ q ） based on the single grid were proposed. In each area, the function of the indexes and different resolutions was obtained so that the needed resolution can be calculated if the index is known. The function is helpful in selecting proper resolutions, minimizing the amount of data and cutting down the cost while ensuring the accuracy of aspect information.