DEM重采样坡度衰减分析

通过数字高程模型(DEM)重采样发现,随着水平分辨率的降低,地形也随着趋向平缓,坡度信息不断丢失,地面表达能力逐步下降.利用1∶10 000数字地形图生成5m水平分辨率DEM,以此为基准重采样生成10、20、40m水平分辨率的DEM,提取各水平分辨率DEM的坡度.对提取的5m水平分辨率DEM的坡度进行邻域分析,提取10、20、40m水平分辨率DEM的最大坡度,以此求取其与直接由相对应水平分辨率DEM提取的坡度的差值,并对坡度差值进行频率统计分析,同时分析了剖面曲率在重采样过程中的变化.结果表明,随着DEM水平分辨率的降低,坡度平均值不断降低,较小坡度的频率逐渐增大,较大坡度的频率逐渐减小.DEM水平分辨率较高时,坡度差值分布集中于较小坡度差值处,且范围集中;DEM水平分辨率越低,坡度差值分布曲线愈加分散,且集中于较大坡度差值处.DEM水平分辨率越高,剖面曲率曲线分布越广,DEM水平分辨率越低,曲线分布越窄,且变得集中,其中剖面曲率较高部分损失严重.

Analysis on Slope Attenuation Caused by DEM Re-sampling

Using 1∶10 000 digital topographic maps,digital elevation model(DEM) with resolution of 5 m DEM was generated,based on which DEM with resolution of 10,20 and 40 m was re-sampled.The slopes of these DEM was calculated.Neighboring region analysis was conducted on DEM with resolution of 5 m;and the maximum value on the 10,20 and 40 m resolution was extracted so that its difference from the slope directly extracted from DEM with corresponding resolution could be calculated for frequency statistics.The results showed that the average of slope decreased as the resolution of DEM decreased;and the frequency of small slope increased while of large slope decreased.When DEM resolution was high,the difference concentrated in the small slopes.The lower DEM resolution,the more disperse the difference distribution curves,and concentrated in the large slope.The higher DEM resolution,the wider the profile curvature curves was,and vice versa;moreover,the curves was more concentrated and the section with higher profile curvature was seriously lost.