As one of the main forms of soil erosion on the hilly Loess Plateau,gully erosion threatens the land resources and causes serious environmental problems.Although different approaches have been used to monitor and predict gully erosion over the years,gully erosion measurement on middle and large scale is still difficult.The objective of this study was to assess the accuracy of measuring gully morphological parameters using stereoscopic satellite images with very high resolution on the hilly Loess Plateau and feasibility of stereoscopic satellite images acting a reliable data source for large scale gully erosion monitoring.GeoEye-1 stereoscopic satellite images (0.5 m panchromatic and 2.0 m multispectral images,acquired in March,2016) were used to calculate gully morphological parameters of 21 gullies in a catchment located in central Loess Plateau and then test their accuracy by comparing them with 3D (three-dimensional) laser scanning data (0.15 m resolution,acquired in July,2016),and mean error,percent error and root mean squared error were used for error measure.The results were as follows:1) The average errors of linear and areal gully parameters,including area,perimeter,length and width,were 3.58 m2,0.55 m,0.13 m and-0.10 m,respectively,and the percentage errors were 0.11％-33.81％,0.41％-18.58％,0.10％-12.28％,and 0.09％-37.41％,with the average percentage error of 8.96％,4.83％,2.92％,and 10.81％,respectively.The percentage errors of area,perimeter,and length were mainly below 5％,and the percentage errors of gully width were mainly below 10％.Overall,the errors of linear and areal gully parameters extracted from high resolution stereoscopic satellite images can be controlled in a lower level.2) The average errors of 3D gully parameters,including gully bottom width,maximum gully depth,average gully depth,cross sectional area and gully volume,were-0.67 m,0.14 m,-0.46 m,-6.30 m2 and-54.01 m3,respectively.The percentage errors of 3D gully parameters were 0.39％-84.65％,0.51％-55.91％,0-59.64％,0.13％-81.53％,and 1.98％-88.72％,respectively,with the average percentage error of 30.37％,24.13％,27.16％,37.96％ and 37.46％,respectively.The percentage errors of 3D gully parameters were mainly below 50％ except the maximum gully depth which was mainly below 30％.Compared with 3D laser scanning,gully bottoms morphology measured with stereoscopic satellite images presented smaller gully depths,gully bottom width and cross sectional area.3) 3D gully parameters including gully volume,cross sectional area and gully bottom width were correlated significantly with gully scale at the level of 0.05.The larger the scale of the gullies,the smaller the measured gully volume,cross sectional area and gully bottom width from stereoscopic satellite images than 3D laser scanning measurement.A linear regression model was built between measurement errors and gully volumes,which can be used when other measurement approaches are not available.On the whole,the accuracy of measured gully parameters from stereoscopic satellite images will be affected by many factors,such as the resolution of stereoscopic satellite images,the correction accuracy and the number of control points,but it also can provide reliable data for linear and areal gully parameters measurement and new method for 3D parameters measurement of large scale gullies on the hilly Loess Plateau.%为了研究高分立体像对测量黄土丘陵区切沟参数的适用性,选取陕北黄土区合沟小流域,以三维激光扫描全站仪获取的数据为参照值,分析使用GeoEye-1高分遥感立体像对测量切沟参数的精度,得到如下研究结果.1)刃沟面积、周长、沟长和沟宽等线状和面状参数平均测量误差分别为3.58 m2,0.55 m,0.13m和-0.10 m,其中面积、周长和沟长的百分误差主要集中在5％以内,沟宽百分误差主要分布在10％以内.2)切沟三维参数沟底宽、最大沟深、平均沟深的平均测量误差分别为-0.67、0.14和-0.46 m.截面积和体积的平均误差分别为-6.30 m2和-54.01 m3.最大沟深的百分误差主要集中在30％以内,沟底宽、平均沟深、截面积和体积的百分误差则主要分布在50％以内;相较于三维激光扫描的切沟,立体像对提取的切沟沟底形态误差较大,主要是沟底宽和平均沟深偏小.3)切沟规模越大,切沟体积、截面积和沟底宽的测量值偏小的幅度越大.但是,切沟体积测量误差与切沟体积之间可以建立较好的线性回归模型,在缺少其他测量手段时,可以使用该模型对测量误差进行校正.总体上看,高分立体遥感为切沟线状和面状参数测量以及切沟体积测量提供了新的方法,为黄土丘陵区沟蚀监测提供了便捷、且相对可靠的数据源.
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