Retrieval of Forest Structural Parameters from Terrestrial Laser Scanning: A Romanian Case Study

Abstract

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 122kpts 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 (0.02m) 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).

Modelling and Comparing Shading Effects of 3D Tree Structures with Virtual Leaves

“…The development of the shadow model can be divided in four parts (Parts A-D, see Figure 1 To update our shadow model, the six wild cherry trees were scanned with a TLS Faro Focus 3D S120 (FARO Technologies, Inc.; Lake Mary, FL, USA) in early spring (April 2019), under windless and leaf-off conditions, for a better visibility of the woody compartments of the trees [48]. The scanned tree surface is representative of the last growing season.…”

Applications of TLS and ALS in Evaluating Forest Ecosystem Services: A Southern Carpathians Case Study

“…The airborne LiDAR data for the one-hectare plots were collected through the use of a full-wave airborne laser scanner [60]. The discrete points extraction was conducted by Regarding the TLS pre-processing methods for classification and segmentation of the point cloud prior to obtaining the stems and the foliage, an approach proposed by Pascu et al was followed [24,30,32,59] (Figure 2b).…”

“…New technologies, as is the case of terrestrial laser scanning, propose different approaches for estimating tree characteristics. These provide a more direct method that involves point cloud classification, tree segmentation, and stem reconstruction [30][31][32]. Besides the biophysical parameters, active remote-sensing systems are used to describe stands' structure through indirect analyses of the number of trees, canopy stratification, and trees distribution.…”

Development of Mathematical Models for the Estimation of Dendrometric Variables Based on Unmanned Aerial Vehicle Optical Data: A Romanian Case Study

“…Applied in stands characterized by variations in crown size and Kraft class, the detection rate of trees can be as high as 97.4% when DBH is above 12 cm, and 84.62% when DBH is below this threshold (as is the case in natural regenerations) [22]. However, research has also highlighted the potential limitations of using TLS, rooted in the complexity of crown structure [23].…”