Airborne laser scanning applied to eucalyptus stand inventory at individual tree level

Abstract: The objective of this work was to evaluate the application of airborne laser scanning (ALS) to a large-scale eucalyptus stand inventory by the method of individual trees, as well as to propose a new method to estimate tree diameter as a function of the height obtained from point clouds. The study was carried out in a forest area of 1,681 ha, consisting of eight eucalyptus stands with ages varying from four to seven years. After scanning, tree heights were obtained using the local maxima algorithm, and total wood stock by summing up individual volumes. To determine tree diameters, regressions fit using data measured in the inventory plots were used. The results were compared with the estimates obtained from field sampling. The equation system proposed is adequate to be applied to the tree height data derived from ALS point clouds. The tree individualization approach by local maxima filters is efficient to estimate number of trees and wood stock from ALS data, as long as the results are previously calibrated with field data.

摘要：本研究旨在评估机载激光扫描（Airborne Laser Scanning, ALS）以单木方法开展大规模桉树林分调查的应用可行性，并提出一种基于点云获取的树高数据估算树木直径的新方法。本研究在一片面积为1681公顷的林区开展，该林区包含8个林龄介于4至7年的桉树林分。扫描完成后，采用局部极大值算法获取树木高度，并通过累加单木材积得到总木材蓄积量。树木直径的估算则利用由调查样地实测数据构建的回归模型完成。将上述估算结果与野外采样获取的结果进行对比。结果表明，所提出的方程组可有效应用于由ALS点云衍生的树高数据。基于局部极大值滤波的单木识别方法可高效地从ALS数据中估算林木株数与总木材蓄积量，前提是需预先利用野外实测数据对结果进行校准。