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首页> 外文期刊>International journal of remote sensing >Estimation of tree crown volume from airborne lidar data using computational geometry
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Estimation of tree crown volume from airborne lidar data using computational geometry

机译：使用计算几何从机载激光雷达数据估计树冠体积

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摘要

Although simple geometrical shapes are commonly used to describe tree crowns, computational geometry enables calculation of the individual crown properties directly from airborne lidar point clouds. Our objective was to calculate crown volumes (CVs) using this technique and validate the results by comparing them with field-measured values and modelled ellipsoidal crowns. The CVs of standing trees were obtained by measuring the crown radii at different heights, integrating the obtained crown profiles as solids of revolution, and finally averaging the volumes obtained from the four separate profiles. With the lidar data, the CVs were extracted using 3D alpha shape and 3D convex hull techniques. Crown base heights (CBHs) were also estimated from the lidar data and used to exclude echoes from the understory, which was also done using field-based CBHs to exclude this error source. The results show that the field-measured CVs had a high correlation with lidar-based estimates (best R~2 = 0.83), but the lidar-based estimates were generally smaller than the field values. The best correspondence (root mean square difference (RMSD) = 45.0%, average difference = -24.7%) was obtained using the convex hull of the point data and field-measured CBH. The CBHs were consistently overestimated (RMSD = 37.3%; average difference = -20.0%), especially in spruces with long crowns. Thus using lidar-based CBH also increased the inaccuracy of the CV estimates. While the underestimation of CV is mainly explained by the inadequate number of echoes from the lower regions of the crowns, the CVs obtained from the lidar were better than those obtained with ellipsoids fitted by using general models for crown dimensions. The utility of the estimated CVs in the prediction of stem diameter is also demonstrated.
机译：尽管通常使用简单的几何形状来描述树冠，但计算几何可以直接从机载激光雷达点云计算单个树冠的属性。我们的目标是使用这种技术来计算牙冠体积（CV），并通过与实测值和建模的椭圆形牙冠进行比较来验证结果。通过测量不同高度的树冠半径，将获得的树冠轮廓作为旋转实体进行积分，最后平均从四个单独的轮廓中获得的体积，可以得出站立树木的CV。利用激光雷达数据，使用3D alpha形状和3D凸包技术提取CV。冠底高度（CBH）也从激光雷达数据中估算出来，并用于排除地下层的回波，这也可以使用基于现场的CBH来排除此误差源。结果表明，现场测量的CV与基于激光雷达的估计值具有高度相关性（最佳R〜2 = 0.83），但基于激光雷达的估计值通常小于现场值。使用点数据的凸包和现场测量的CBH，可获得最佳对应关系（均方根差（RMSD）= 45.0％，平均差= -24.7％）。 CBH始终被高估（RMSD = 37.3％；平均差异= -20.0％），特别是在长冠的云杉中。因此，使用基于激光雷达的CBH也增加了CV估计的不准确性。尽管对CV的低估主要是由来自冠下部区域的回波数量不足引起的，但从激光雷达获得的CV优于通过使用一般尺寸冠模型拟合的椭圆体获得的CV。还证明了估计的CV在茎直径的预测中的实用性。

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  • 来源
    《International journal of remote sensing》 |2013年第20期|7236-7248|共13页
  • 作者

    Lauri Korhonen; Jari Vauhkonen; Ami Virolainen; Aarne Hovi; Ilkka Korpela;

  • 作者单位

    School of Forest Sciences, University of Eastern Finland, Joensuu, Finland;

    Department of Forest Sciences, University of Helsinki, Helsinki, Finland;

    School of Forest Sciences, University of Eastern Finland, Joensuu, Finland;

    Department of Forest Sciences, University of Helsinki, Helsinki, Finland;

    Department of Forest Sciences, University of Helsinki, Helsinki, Finland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
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