Most crops in northern China are irrigated,but the topography affects the water use,soil erosion,runoff and yields.Technologies for collecting high-resolution topographic data are essential for adequately assessing th...Most crops in northern China are irrigated,but the topography affects the water use,soil erosion,runoff and yields.Technologies for collecting high-resolution topographic data are essential for adequately assessing these effects.Ground surveys and techniques of light detection and ranging have good accuracy,but data acquisition can be time-consuming and expensive for large catchments.Recent rapid technological development has provided new,flexible,high-resolution methods for collecting topographic data,such as photogrammetry using unmanned aerial vehicles(UAVs).The accuracy of UAV photogrammetry for generating high-resolution Digital Elevation Model(DEM)and for determining the width of irrigation channels,however,has not been assessed.A fixed-wing UAV was used for collecting high-resolution(0.15 m)topographic data for the Hetao irrigation district,the third largest irrigation district in China.112 ground checkpoints(GCPs)were surveyed by using a real-time kinematic global positioning system to evaluate the accuracy of the DEMs and channel widths.A comparison of manually measured channel widths with the widths derived from the DEMs indicated that the DEM-derived widths had vertical and horizontal root mean square errors of 13.0 and 7.9 cm,respectively.UAV photogrammetric data can thus be used for land surveying,digital mapping,calculating channel capacity,monitoring crops,and predicting yields,with the advantages of economy,speed and ease.展开更多
目前,ICESat/GLAS是大尺度GDEM(global public digital elevation model)精度评价和修正的主要数据源。然而,现有的修正方法均忽略了两组数据之间的有效配准。为此,选取江西省作为研究区域,以SRTM1和ALOS作为研究对象,使用随机森林(rand...目前,ICESat/GLAS是大尺度GDEM(global public digital elevation model)精度评价和修正的主要数据源。然而,现有的修正方法均忽略了两组数据之间的有效配准。为此,选取江西省作为研究区域,以SRTM1和ALOS作为研究对象,使用随机森林(random forest,RF)对配准前、配准后SRTM1和ALOS修正,以验证数据配准对GDEM修正的重要性。研究结果表明:ICESat/GLAS与SRTM1之间不存在位置偏差,而与ALOS之间存在明显的位置偏差;和配准前相比,配准后ALOS的系统误差基本消除,中误差也降低了10.0%,证明数据配准对ALOS精度有重要影响。RF方法可以显著提高SRTM1和ALOS的精度,但配准后ALOS修正精度明显优于配准前,其精度多提高了21.5%,再次证明数据配准对ALOS修正影响较大。和原始DEM相比,修正后SRTM1和ALOS的平均误差均接近于0 m,平均绝对误差和中误差也分别降低了11.9%、37.0%和15.1%、29.2%。展开更多
基金This work was financially supported by Major Project of National Key R&D Plan from the MOST of China(2017YFC0403203)National Natural Science Foundation of China(41771315,41301283,61402374,41371274,41301507)+2 种基金Natural Science Foundation of Shaanxi Province(2015JM4142)EU Horizon 2020 research and innovation programme(ISQAPER:635750)State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(A314021402-1702).
文摘Most crops in northern China are irrigated,but the topography affects the water use,soil erosion,runoff and yields.Technologies for collecting high-resolution topographic data are essential for adequately assessing these effects.Ground surveys and techniques of light detection and ranging have good accuracy,but data acquisition can be time-consuming and expensive for large catchments.Recent rapid technological development has provided new,flexible,high-resolution methods for collecting topographic data,such as photogrammetry using unmanned aerial vehicles(UAVs).The accuracy of UAV photogrammetry for generating high-resolution Digital Elevation Model(DEM)and for determining the width of irrigation channels,however,has not been assessed.A fixed-wing UAV was used for collecting high-resolution(0.15 m)topographic data for the Hetao irrigation district,the third largest irrigation district in China.112 ground checkpoints(GCPs)were surveyed by using a real-time kinematic global positioning system to evaluate the accuracy of the DEMs and channel widths.A comparison of manually measured channel widths with the widths derived from the DEMs indicated that the DEM-derived widths had vertical and horizontal root mean square errors of 13.0 and 7.9 cm,respectively.UAV photogrammetric data can thus be used for land surveying,digital mapping,calculating channel capacity,monitoring crops,and predicting yields,with the advantages of economy,speed and ease.
文摘目前,ICESat/GLAS是大尺度GDEM(global public digital elevation model)精度评价和修正的主要数据源。然而,现有的修正方法均忽略了两组数据之间的有效配准。为此,选取江西省作为研究区域,以SRTM1和ALOS作为研究对象,使用随机森林(random forest,RF)对配准前、配准后SRTM1和ALOS修正,以验证数据配准对GDEM修正的重要性。研究结果表明:ICESat/GLAS与SRTM1之间不存在位置偏差,而与ALOS之间存在明显的位置偏差;和配准前相比,配准后ALOS的系统误差基本消除,中误差也降低了10.0%,证明数据配准对ALOS精度有重要影响。RF方法可以显著提高SRTM1和ALOS的精度,但配准后ALOS修正精度明显优于配准前,其精度多提高了21.5%,再次证明数据配准对ALOS修正影响较大。和原始DEM相比,修正后SRTM1和ALOS的平均误差均接近于0 m,平均绝对误差和中误差也分别降低了11.9%、37.0%和15.1%、29.2%。
