A Theoretical Examination of Systematic Error in Crown Volume Estimation from Line-Transects by Airborne Laser Altimetry

Abstract

Previous studies have revealed wide variation in forest stand volume estimations derived from forest canopy profiles that were detected using a line-transect method of airborne laser altimetry, or LiDAR (Light Detection and Ranging). We suggest the possibility that a detected canopy profile may not accurately represent the true stand profile. For example, a vertical profile detected by LiDAR may not always intersect the tree crown centerline. We theoretically examined projected individual crown volume, which is normally estimated using the corresponding individual vertical crown profile. The results suggest there should theoretically be no bias in the projected crown volume, regardless of crown profile. On the other hand, the results also suggest that variation in projected crown volume can be greater when the canopy is not closed and/or when the crown features a sharper top.