摘要 【目的】获取森林单木参数的信息是经营、管理森林过程中的一项重要内容。倾斜摄影测量技术以其多角度拍摄方法,成为目前高效获得单木信息的研究方法之一。【方法】本研究以内蒙古旺业甸油松林为研究对象,利用无人机倾斜摄影测量技术获取油松单木的树高、冠幅和材积,探究了4种不同的相片分辨率(1、0.5、0.25、0.1 m)对单木信息提取能力的影响。采用基于点云数据的均值漂移算法和基于冠层高度模型(CHM)的分水岭算法分割单木树冠,以样地实测单木参数和激光雷达提取的单木数据作为验证数据,探索了相片分辨率与单木提取能力的关系,比较了两种分割方法的准确度及最优分辨率。建立了基于CHM提取树高与单木材积的异速生长模型(y=0.0001x2.717,R2=0.5717),并绘制了测区油松单木材积分布图。【结果】(1)摄影测量提取单木油松冠幅,分水岭算法和均值漂移分割算法均在0.5 m相片分辨率的分割准确度最好,且分水岭算法提取的冠幅较均值漂移算法有较少的漏分、过度分割,其F得分分别为0.87和0.82;而在0.5 m分辨率下均值漂移算法提取的冠幅数值准确度较好,分水岭算法和均值漂移算法得到的参考树冠与分割树冠的相关系数分别为0.850和0.892,且在P<0.01水平上极显著。(2)分水岭分割算法和均值漂移算法提取油松树高的能力相近,0.5 m相片分辨率得到的单木树高平均误差最小且相差不大,分别为0.42和0.66 m。【结论】研究明确了倾斜摄影测量技术提取油松单木的关键方法和最佳相片分辨率参数,提高了调查效率,为设置合理无人机数据获取的参数提供了科学依据。 [Objective]It is an important content in the process of forest management to obtain the information of single wood parameters.Oblique photogrammetry has become one of the most efficient methods to obtain single wood information with its multi-angle shooting method.[Method]In this study,taking Chinese pine forest in Wangyedian,Inner Mongolia of northern China as the research object,the tree height,crown width and stem volume were obtained by UAV tilt photography,and the effects of four different photo resolutions(1,0.5,0.25,0.1 m)on the information extraction ability of single tree were investigated.The mean-shift algorithm based on the point cloud data and the watershed algorithm based on CHM were used to segment the single tree crown.Taking the measured single tree parameters of the sample plot and the single tree data extracted by LiDAR as the verification data,the relationship between the resolution of photo and the extraction ability of single tree was explored,and the accuracy and the optimal resolution of the two segmentation methods were compared.The allometric model(y=0.0001x2.717,R2=0.5717)was established to extract tree height and volume with CHM,and the volume distribution map of Chinese pine in the survey area was drawn.According to the experimental results,the key parameters of oblique photogrammetry,such as the reasonable resolution requirements of UAV photos and the flight altitude range were obtained.[Result]The watershed algorithm and mean-shift algorithm had the best segmentation accuracy at 0.5 m photo resolution,and the canopy extracted by watershed algorithm had less missing points and over segmentation than mean shift algorithm,with F-scores of 0.87 and 0.82,respectively.While at the resolution of 0.5 m,the crown value extracted by mean-shift algorithm was more accurate.The correlation coefficients between the reference crown and the segmented crown obtained by watershed algorithm and mean-shift algorithm were 0.850 and 0.892,respectively,which were very significant at the level of 0.0
出处 《北京林业大学学报》 CAS CSCD 北大核心 2021年第4期77-86,共10页 Journal of Beijing Forestry University
基金 国家重点研发计划(2017YFD0600900) 国家级大学生创新创业训练计划(G201910022004)。
关键词 倾斜摄影 树高 冠幅 材积 分水岭分割算法 均值漂移算法 oblique photogrammetry tree height crown width stem volume watershed segmentation algorithm mean-shift algorithm
