Research Highlights: The present study case investigates the differences occurring when tree’s biophysical parameters are extracted through single and multiple scans. Scan sessions covered mountainous and hill regions of the Carpathian forests. Background and Objectives: We focused on analyzing stems, as a function of diameter at breast height (DBH) and the total height (H), at sample plot level for natural forests, with the purpose of assessing the potential for transitioning available methodology to field work in Romania. Materials and Methods: We performed single and multiple scans using a FARO Focus 3D X130 phase shift terrestrial laser scanner at 122 kpts and 0.3:0.15 mm noise compression ratio, resulting in an average point density of 6pts at 10m. The point cloud we obtained underpinned the DBH and heights analysis. In order to reach values similar to those measured in the field, we used both the original and the segmented point clouds, postprocessed in subsamples of different radii. Results: Pearson’s correlation coefficient above 0.8 for diameters showed high correlation with the field measurements. Diameter averages displayed differences within tolerances (0.02 m) for 10 out of 12 plots. Height analysis led to poorer results. For both acquisition methods, the values of the correlation coefficient peaked at 0.6. The initial hypothesis that trees positioned at a distance equivalent to their height can be measured more precise, was not valid; no increase in correlation strength was visible for either heights or diameters as the distance from scanner varied (r = 0.52). Conclusions: With regard to tree biophysical parameters extraction, the acquisition method has no major influence upon visible trees. We emphasize the term “visible”, as an increase in the number of acquisitions led to an increased number of detected trees (16% in old stands and 29% in young stands).

中文翻译：

---

陆地激光扫描反演森林结构参数：罗马尼亚案例研究

研究重点：本研究案例调查了通过单次和多次扫描提取树木的生物物理参数时发生的差异。扫描会议覆盖了喀尔巴阡山脉的山区和丘陵地区。背景与目标：我们专注于分析天然林的样地水平上随胸高直径（DBH）和总高（H）而变的茎，目的是评估将可用方法过渡到田间的潜力在罗马尼亚工作。材料和方法：我们使用FARO Focus 3D X130相移地面激光扫描仪以122 kpts和0.3：0.15 mm的噪声压缩比执行了单次和多次扫描，在10m处的平均点密度为6pts。我们获得的点云为DBH和高度分析奠定了基础。为了达到类似于现场测量的值，我们使用原始和分段的点云，并在不同半径的子样本中进行了后处理。结果：直径的皮尔森相关系数高于0.8，与现场测量结果显示出高度相关性。直径平均值在12个图中的10个图中显示在公差（0.02 m）内的差异。高度分析导致较差的结果。对于这两种采集方法，相关系数的峰值均为0.6。最初的假设是，可以更精确地测量位于等于其高度的距离处的树木的说法，但这是无效的。随着距扫描仪的距离变化（r = 0.52），相关强度无论是高度还是直径都没有增加。结论：关于树木生物物理参数的提取，采集方法对可见树木没有重大影响。我们强调“可见”一词，因为收购数量的增加导致被检测树木的数量增加（老林分16％，年轻林分29％）。