基于光流法地形跟随的矿区复杂地形无人机摄影测量

受开采沉陷或地表资源剥离的影响,矿区地形一般较为复杂。传统摄影测量作业时根据矿区平均高程和测量精度要求,设计一个固定航高,按照该高度进行无人机影像采集。该方法因受地形起伏的影响,测区内摄影比例尺、影像重叠度、分辨率相差较大,导致测量精度不一致,甚至无法构成立体视觉条件,导致空三加密失败。为克服传统方法的不足,在分析地形起伏对测量精度影响的基础上,基于地形跟随技术,采用轻小型机器视觉模块,通过设计开发基于拓扑约束的快速光流估计算法,实时估计无人机相对地面的航高,并根据地形变化调整无人机飞行高度,实现实时地形跟随的矿区复杂地形摄影测量,从而保证在矿区复杂地形条件下摄影比例尺、影像重叠度、分辨率一致,满足精度均匀的摄影测量条件。研究表明:在矿区复杂地形条件下,能够达到1∶500大比例尺矿区地形图测绘精度要求,证明了该方法的有效性。

Unmanned Aerial Vehicle Photogrammetry for Mining Area Complex Terrain Based on Optical Flow Terrain Following

Affected by mining subsidence or surface resources stripping，the terrain of mining area is generally complex.In the traditional photogrammetry，a fixed aerial height is designed according to the requirements of average terrain and precision in the mining area，and UAV （Unmanned aerial vehicle） image collection is carried out according to this height. Due to the influence of topographic fluctuation，the photographic scale，image overlap degree and resolution difference in the measurement area are large，resulting in inconsistent measurement accuracy，even can not constitute stereoscopic visual conditions，air triangulation encryption failure.In order to overcome the shortcomings of traditional methods，on the basis of analyzing the influence of topographic relief on measuring accuracy，combing with the terrain following technique，the light and small machine vision module is adopted，the relative altitude of the UAV in real time can be estimated through developing the fast optical flow estimation algorithm based on topology constraints，besides that，the UAV flying height can be adjusted based on the changes of terrain，so as to realize the photogrammetry method of complex terrain in mining areas with real-time terrain tracking.In this way， the uniform photographic scale，image overlap and resolution can be guaranteed under the complex terrain conditions of the mining area，and the uniform photogrammetry can meet the requirements of expected accuracy.The study results show that the accuracy of 1∶500 large scale topographic map can be achieved in the complex terrain of mining area，which proves the effectiveness of the method.