基于改进α-shape算法的三维点云树冠体积计算方法  

Calculation Method of 3D Point Cloud Canopy Volume Based on Improvedα-shape Algorithm

作　　者：程钢[1] 王敬宇 杨杰 赵宗泽 王磊[1] CHENG Gang;WANG Jingyu;YANG Jie;ZHAO Zongze;WANG Lei(School of Surveying and Land Information Engineering,Henan Polytechnic University,Jiaozuo 454000,China;Dean's Office,Henan Polytechnic University,Jiaozuo 454000,China)

机构地区：[1]河南理工大学测绘与国土信息工程学院,焦作454000 [2]河南理工大学教务处,焦作454000

出　　处：《农业机械学报》2021年第5期175-183,共9页Transactions of the Chinese Society for Agricultural Machinery

基　　金：国家重点研发计划项目(2016YFC08033103);国家自然科学基金项目(41001226);国家自然科学基金青年基金项目(41801318);中国博士后科学基金面上项目(2015M582831);河南省高校基本科研业务费专项资金项目(NSFRF180329)。

摘　　要：为准确测量树冠体积,深入研究三维绿量和区域碳循环,针对现有点云数据测量树冠体积方法存在的高估与低估问题,提出了一种顾及点云边界密度、变阈值α-shape边界提取方法,并通过实验分析确定最优线性迭代步长和分层间距,实现了对树冠体积的精确计算。首先,对树冠点云数据进行等间距切片处理;然后,采用改进α-shape算法提取点云切片更为真实、自然的边界多边形;最后,计算切片面积和各层点云间的台体体积,并累加台体体积,获得树冠体积。实验表明:树冠体积计算的准确性与树冠内部枝叶结构和点云密度相关;无论对于高密度还是低密度树冠,采用改进α-shape算法的树冠体积计算结果不仅具有良好的稳定性,而且相较于已有其他方法更为准确,避免了Graham凸包算法的高估问题,与体元累加法相比也更利于树冠总体占用空间的计算。Canopy volume is an important tree measurement factor for trees,and the accurate measurement of its volume value plays an important role in the in-depth study of three-dimensional green quantity and regional carbon cycle.Aiming at the problems of overestimation and underestimation in the existing methods of measuring tree canopy volume from point cloud data,aα-shape boundary extraction method that took into account the point cloud boundary density and variable threshold was proposed.The length of the optimal linear-iterative step and the interval between layers of the method were determined through experimental analysis,so as to realize the accurate calculation of canopy volume.Firstly,the canopy point cloud data was sliced at equal intervals;then,an improvedα-shape algorithm was used to extract the more realistic and natural boundary polygons of the point cloud slices;finally,the section area and the volume of the platform between each layer point cloud were calculated,and the canopy volume was obtained by adding the platform volumes.The experimental results showed that the accuracy of obtaining the canopy volume was related to the structure of branches and leaves inside the canopy and the point cloud density.Regardless of high-density or low-density canopies,the canopy volume value calculated by the improvedα-shape algorithm not only had good stability,but also was more accurate than that of existing methods,which avoided the overestimation of Graham convex hull algorithm,and was more conducive to the calculation of the overall volume of the canopy compared with the volume element accumulation method.

关 键 词：树冠体积 点云数据 边界提取 改进α-shape算法 

分 类 号：P225.2[天文地球—大地测量学与测量工程]