Influence of measurement set-up of ground-based LiDAR for derivation of tree structure

The objectives of this research were to investigate (1) the influence of a geometric laser measurement pattern and (2) the shadow effect on the accuracy of a quantitative mathematical description of individual tree structure using a terrestrial laser system. The commercially available SICK Laser-Measurement-System-200 (LMS200, Sick, A.G.) was used in this study to obtain 3D structural datasets with high point densities. An artificial tree was constructed in an experimental set-up, thereby creating the possibility to arrange the structural key elements (leaves and branches) according to predetermined patterns. The multidirectional accuracy and quality of the laser measurement set-ups (lateral sideway, lateral bottom-up, hemispherical bottom-up) subsequently were compared based on the development of a mathematical description of each case. Vertical plant profiles were computed for the different experimental set-ups showing the direct influence of the vertical distribution pattern of the laser beams on the estimation of plant material in a certain height bin. The main measurement direction proved to have the biggest impact on the quality of the dataset, since the derived vertical profile followed the main trend of this laser beam distribution pattern. The use of probability-based statistics was necessary to correct the vertical profiles in order to obtain an acceptable estimation of the amount of plant material per height bin of 0.05 m.