三种重采样方法对冲沟坡度坡长因子的影响

Difference Analysis of Three Resampling Methods for Calculating LS of Gullies Different in Development Stage

为探索不同重采样方法对形态差异明显的冲沟坡度坡长(Slope length and slope steepness,LS)因子的影响,以元谋县干热河谷1∶5 000比例尺的等高线矢量数据为基础,在Arc GIS平台下构建六条典型冲沟2 m分辨率的数字高程模型(Digital elevation model,DEM),采用最邻近(Nearest,Near)、双线性(Bilinear,Bil)、三次卷积(Cubic,Cub)重采样的DEM计算LS,通过相对差系数、LS因子分级面积比例、XY散点图对比分析三种重采样方法计算冲沟LS的差异性。结果表明:Near重采样计算的LS值与Bil、Cub重采样计算的LS值差异较大,相关程度低,Bil与Cub重采样计算的LS值差异较小,相关程度高;冲沟刚发育时,Cub重采样要优于Near和Bil,冲沟侵蚀强烈时,Near重采样要优于Bil和Cub,冲沟形态稳定时,Bil重采样要优于Cub和Near。

【Objective】Multi-resolution DEM（digital elevation model）resample plays the important role in multi-scale DEM conversion,this paper was aiming to investigate influences of the use of difference resampling methods to calculate LS of gullies different in development stage. 【Method】Based on the vector data in the 1∶5 000 scale contour map of the Ganre River Valley in Yuanmou County,DEMs,2 m in resolution,of six typical gullies were established on the Arc GIS platform,using three different resampling methods,known as Near（Nearest neighbor）,Bil（Bilinear interpolation）and Cubic（Cubic convolution）,and LS（Slope Length and Slope Steepness,LS）calculated for comparison quantitatively. Differences between the three methods in LS calculation were analyzed by comparison of the methods in relative difference coefficient,area percentage of LS factor grades,and XY scatter plot.【Result】Results of the paper are summarized as follows：（1）Near is significantly different from Bil and Cub in LS value,while Bil and Cub methods have no significant difference between each other;（2）Bil,rather than Near and Cub,is the most appropriate choice for gullies at their young stage;Near is better than Bil and Cub for gullies at their erosion stage;Cub is more suitable than Near and Bil for gullies at their stable stage.【Conclusion】In conclusion,the research described in this paper has shown that the choice of resampling methods has potentially important consequences for the calculation of LS value of gullies different in development stage.