Application and statistical analysis of terrestrial laser scanning and forest growth simulations to determine selected characteristics of Douglas-Fir stands.

Abstract

Among others, the dbh, basal area, and tree height are the most important parameters to describe tree dimensions in forest inventories. In traditional forest inventories, these parameters are measured manually. In times of forest staff reduction and amalgamation of forest districts, terrestrial laser scanning (TLS) could evolve as a fast, efficient and automatic tool for the determination of basic inventory parameters such as the number of trees, diameter at breast height (dbh), basal area, tree height as well as stem and crown shape parameters. Since there has so far been little attention drawn to the accuracy and precision of TLS itself, we statistically investigated TLS in comparison with traditional inventory methods. We developed an investigation procedure, exemplified for a 49-year-old Douglas-Fir stand (Pseudotsuga menziesii var. Viridis Mirb.) near Eberswalde in the northeastern part of Germany to analyse the potential of TLS in terms of diameter at breast height (dbh) and height measurements. The results of the study suggest that the precision of the dbh measured from the laser scan point cloud return is sufficient. However, TLS was linked to an underestimation of dbh in comparison to the reference values measured with a diameter tape. Stand volume was accurately measured only if multiple scan positions were distributed in the forest stand.