基于无人机贴近摄影测量的坡面细沟侵蚀及形态演化研究

Slope Rill Erosion and Morphological Evolution Based on UAV Nap-of-the-object Photogrammetry

[目的]寻求效率和精度均高且适应性强的坡面细沟侵蚀测量技术手段,克服传统测量方法效率低,成本高,适用性差等问题,为坡面细沟侵蚀演变过程及定量化研究提供新的思路和技术手段。[方法]利用无人机通过贴近摄影测量获取连续6场人工模拟降雨下坡面细沟发育的高分辨率影像及模型,经定位精度、模型精度和侵蚀模拟3个方面验证,定量揭示坡面细沟侵蚀及形态演化过程的可行性。[结果](1)三维实景模型地理配准均方根误差RMSE_(3D)=1.5 cm,像控点平面误差RMSE_(H)=0.42 cm,高程误差RMSE_(V)=0.88 cm,模型细节及纹理清晰,分辨率达到毫米级。(2)多期模型能够清晰刻画细沟发育经历的雨滴溅蚀—片蚀—小跌水—断续细沟—连续细沟5个阶段。坡面细沟平均沟宽、沟深、密度分别从最初的1.25 cm,0.82 cm,0.05发展到最终的3.27 cm,4.75 cm,0.23,最大沟长236 cm,最大沟深14.23 cm。(3)细沟土壤侵蚀量模拟值随着降雨历时的增加不断接近真实值并趋于稳定,平均误差在10%以内。[结论]无人机贴近摄影测量技术能较好地反映细沟发育演化过程,作业效率及便利性较传统测量方法具有显著优势。

[Objective] This study was conducted to determine a rill erosion technology having high efficiency,high accuracy and strong adaptability,and overcome deficiencies associated with traditional measurement methods(low efficiency,high cost,poor applicability,etc.) in order to provide new ideas and technical means for the evolution of slope rill erosion and quantitative research.[Methods] UAV technology was used to acquire high-resolution images and models of rill development on slopes under six consecutive simulated rainfall events by use of nap-of-the-object photogrammetry.The feasibility of slope rill erosion and morphological evolution was quantitatively evaluated by positioning accuracy,model accuracy,and erosion simulation.[Results](1) The root mean square error(RMSE) of geographic registration of the 3D real scene model was 1.5 cm.The image control point plane RMSE was 0.42 cm.The elevation RMSE was 0.88 cm.The model details and texture were clear,with millimeter-level resolution.(2) The multi-phase model clearly described five stages of rill development:raindrop splash erosion,sheet erosion,small waterdrop erosion,intermittent rill erosion,and continuous rill erosion.The average width,depth,and density of rills on the slope surface developed from the initial values of 1.25 cm,0.82 cm,and 0.05 to the final values of 3.27 cm,4.75 cm and 0.23,respectively.The maximum trench length was 236 cm and the maximum trench depth was 14.23 cm.(3) As rainfall duration increased,the simulated values of soil erosion in rills were close to the real values and tended to become stable,with an average error of less than 10%.[Conclusion] UAV nap-of-the-object photogrammetry can better reflect rill development and evolution,and has significant advantages over traditional measurement methods in efficiency and convenience.