Recovering Tree Heights from Airborne Laser Scanner Data

Abstract

Abstract Airborne laser scanner data collected over forests provide a canopy height. To obtain tree heights from airborne laser scanner data one needs a recovery model. Two such models, one (A) assuming that observations are sampled with probability proportional to displayed crown area, and the other (B) derived from the probability that a laser beam penetrates to a given canopy depth, were developed and applied to laser scanner data obtained over stands of Douglas-fir. Model estimates of recovered arithmetic mean tree heights and quantiles (75%, 85%, and 95%) were not significantly (P> 0.24) different from ground-based equivalents. An overall mean bias of-3 m in the laser canopy heights was eliminated by both methods. The median absolute difference between observed and predicted plot means and quantiles were reduced by 40 to 60%. Three alternative recovery procedures are presented for model B. For a single plot, the predictions varied significantly among the models and estimation procedures with no consistent pattern. Predictions of arithmetic mean heights were best for plots with no understory, while predictions of upper quantiles were consistent in all plots. For. Sci. 45(3):407-422.