无人机摄影测量提取黄土高原切沟参数精度分析

Accuracy of gully morphological parameters extracted by UAV photogrammetry in the Loess Plateau

选取陕北黄土丘陵沟壑区桥沟小流域为研究区,分别用同时相的地面三维激光扫描数据和固定翼无人机摄影测量数据提取切沟形态参数,分析无人机摄影测量提取切沟参数的误差及其原因.结果表明:1)无人机摄影测量与三维激光测量比较,提取切沟面积、周长和沟长二维形态参数的百分误差<10%;2)与三维激光扫描测得切沟横截面积、平均沟深和体积三维形态参数相比较,无人机摄影测量误差<20%,沟壁陡峭、植被覆盖度较高的大型切沟测量参数误差较大,而沟壁坡度相对较小、植被相对稀疏的小型切沟测量参数误差较小;3)固定翼无人机垂直摄影采集数据的方式会导致切沟沟壁细节数据缺失,从而降低切沟参数提取精度.基于无人机摄影测量生成的DSM无法有效过滤植被影响,在一定程度上影响切沟参数的提取精度.与三维激光测量相比,无人机摄影测量切沟地貌参数的精度略低,在切沟短期动态变化监测方面还存在一定的局限性.

Unmanned aerial vehicle(UAV) and ground Lidar scanning are 2 new methods used for soil erosion investigation in recent years. However,the accuracy of UAV-generated topography in areas with complex terrain is unclear. To explore applicability of UAV photogrametry in gully erosion monitoring,gully morphological parameters extracted from UAV images by a fixed-wing drone at a flight height of 122 m were compared to ground Lidar scanning data in a small catchment on the hilly and gully Loess Plateau. Percentage errors in 2D gully parameters including area,perimeter and length extracted from UAV image data were found to be <10%. UAV image-extracted 3D gully parameters(ross sectional area,average gully depth and gully volume) showed errors of <20%,with lower errors for small gullies with a gentle gully sidewall and sparse vegetation,higher errors for larger gullies with steep gully sidewall and high vegetation coverage. Errors in gully parameters measured by UAV photogrametry were mainly due to the fact that fixed-wing drones collect data vertically,leading to the loss of sidewall details thus reducing accuracy of parameter extraction. Vegetation showed certain influence on measurement accuracy, due to lack of effective vegetation filtering. Compared with ground Lidar scanning,accuracy of geomorphological parameters from UAV photogrametry was found to be slightly lower,implying limitations in short-term monitoring of gully erosion.