DEM坡度的尺度效应研究

The study on scale effect of DEM slope

DEM的坡度是地形分析中的重要地理因子,随着DEM分辨率的降低,在其上提取的坡度会不断趋于平缓,因而不能如实表现地形起伏。本文重点研究了制图综合和采样间隔两个方面对DEM坡度的影响,利用不同分辨率DEM所提取的坡度的频率和累计频率,并对其进行分级统计,作为数据分析基础。利用制图综合和采样间隔两方面的综合效应对DEM坡度的影响,验证了DEM坡度随其分辨率的降低而发生衰减。针对制图综合生成的DEM具有相同的栅格尺寸,不同的综合平滑度,而不同采样间隔地形图生成的DEM具有相同的综合平滑程度、不同的栅格大小和不同的信息量,对这两种情况下的DEM坡度分别进行了统计分析,结果表明制图综合对1∶25万地形图生成DEM坡度的影响较大,对于其他比例尺地形图生成DEM的坡度衰减影响不明显。采样间隔对于1∶1万比例尺地形图生成不同分辨率DEM的坡度衰减都具有较大影响。

DEM slope decreases along with the reduction of spatial resolution. For the purpose of investigating the attenuation of DEM slope caused by cartographic generalization and changes of sampling interval, taking Xiannangou Catchment in Ansai Shaanxi as an example, the slopes of DEM generated by 1：1000, 1：5000, 1：10000 and 1：250000 topographic digital maps are compared. After statistical analysis, we find that DEM mean slope decreased by the combined effects of cartographic generalization and sampling interval, and slope frequency concentrated in the gradient of the narrower ranges. Furthermore, cartographic generalization has greater impact on DEM slope of 1：25 million map, and sampling interval has a greater effect on the DEM slopes of all scale maps generated by 1：10000 map.