无人机摄影获取单木三维信息方法研究

Method of Obtaining Single-tree Information by UAV Photographers

随着无人机航空摄影测量技术的成熟和发展,改变了传统森林调查的手段,加快了森林调查的数字化、智能化发展。为提高单木因子的采集效率和精度,降低外业的工作强度,基于倾斜摄影测量技术,以多旋翼无人机为数据采集平台,实现了孤立单木的三维点云模型重建。在此基础上,建立了单木三维信息量测算法,提出切割法和投影法两种提取树冠投影面积的方法,并提取树高、树干任意处直径、树冠投影面积、冠幅、树冠表面积、树冠体积6项测树因子参数。结果表明:1)树木的总高度和第一枝下高的提取精度分别为96.28%和95.61%,胸径和上部直径的提取精度分别为96.24%和93.78%;2)利用切割法和投影法提取树冠投影面积的精度分别为96.28%和98.24%,提取冠幅的精度分别为89.65%和91.50%,提取树冠表面积的精度分别为96.78%和97.58%,提取树冠体积的精度分别为94.29%和96.14%;3)实践证明,该技术可很好地应用到古树名木的保护工作中,并可对森林调查的方式提供新的技术参考,具有较高的现实意义和实际应用价值。

With the maturation and development of drone aerial photogrammetry technology,the means of traditional forest surveys have been changed and the digital and intelligent development of forest surveys has been accelerated.In order to improve the collection efficiency and accuracy of single tree factor and reduce the working strength in the field,a 3D point cloud model reconstruction for isolated single tree was realized and based on tilted photogrammetry technology,and used multi-rotor UAV as data acquisition platform. On this basis,a three-dimensional information measurement algorithm for single tree was established,and two methods,cutting method and projection method,were proposed to extract projection area of tree crown,and six parameters of tree height,diameter of tree trunk at any place,projection area of tree crown,crown width,crown surface area and crown volume were extracted.The results show that:1) The total height of the single tree and the height of the first branch were 96.28% and 95.61% respectively,and the DBH and the upper diameter were 96.24% and 93.78% respectively;2) The accuracy of extracting canopy projection area by cutting method and projection method was 96.28% and 98.24%,the accuracy of extracting crown amplitude was 89.65% and 91.50%,respectively,and the accuracy of extracting canopy surface area was 96.78% and 97.58%,respectively,and the accuracy of tree crown volume was 94.29% and 96.14% respectively;3) Practice has proved that this technology can be well applied to the protection of ancient and famous trees,and can provide a new technical reference for the way of forest survey,which has high practical significance and practical application value.