Estimating tree and stand variables in a Corsican Pine woodland from terrestrial laser scanner data

Abstract

A terrestrial laser scanner was used to take four scans of an area of trees, approximately 480 m² in area, within a coniferous tree stand situated in Leicestershire, UK. A number of measurements were extracted from the point cloud and compared with field measurements. Automatic stem recognition was achieved for all stems except those at the edge of the study plot. From the locations of detected stems, diameter at breast height (DBH) was measured with two least-squares shape-fitting algorithms and a circular Hough transformation method; the results were then compared with field measurements. The root mean squared error (RMSE) for DBH measurement from the laser scanner was found to be in the range 0.019–0.037 m, using three measures. Stem density (1031 stems ha⁻¹) and basal area (73 m² ha⁻¹) were also measured with reasonable accuracy. Estimation of tree volume was not as successful, in contradiction to previous research, as upper diameters and heights of trees could not be measured. This was probably a result of previous research being focused on low-density forest stands. This study presents an assessment of laser scanning capabilities in a forest environment with high (1000 stems ha⁻¹) stand density, and finds automation of the analysis to yield some important tree and stand variables to be very effective.