Individual tree measurements in a planted woodland with terrestrial laser scanner

Abstract

Terrestrial light detection and ranging technology provides an accurate measurement of individual tree parameters that areessential for managing forest resources, modeling forest fires, planning forest operations, etc. This study aimed to measure individualtree parameters to model a single tree using terrestrial laser scanner (TLS) data. A high-resolution digital terrain model (DTM) wasgenerated using point cloud data (2,800,430 points) to obtain the tree parameters. Next, the diameter of breast heights (DBH), treeheights, tree lengths, tree projection areas, and crown parameters were calculated using 3D Forest 0.42 software. In order to evaluatethe capabilities of TLS data, estimated tree parameters were compared with the parameters obtained by field measurements. Regressionanalysis and paired sample t-test were performed to compare the DBH and tree height values estimated by TLS with those obtainedfrom field measurements. We found a strong relationship between the field measurements and TLS estimates for DBHs (R2 = 0.99) with1.65 cm root mean square error (RMSE) and tree heights (R2 = 0.98) with RMSE = 0.724 m. The paired Wilcoxon signed-rank test forDBH groups showed no significant difference (P = 0.7285 > 0.05), whereas according to the results of the paired sample t-test for theheight groups, there were significant differences between tree heights (P = 0.015 < 0.05; t = –2.55). The results also indicate that TLSis an effective measurement tool to provide highly accurate and precise results for 3D modelling of tree structure parameters withoutcutting trees. TLS also has great potential to provide many individual tree attributes with high accuracy, which can be used for furtherevaluations in many forestry disciplines such as silviculture, nature conservation, forest management, and urban forestry.