Testing the usability of truncated angle count sample plots as ground truth in airborne laser scanning-based forest inventories

Abstract

Airborne laser scanner (ALS)-based forest inventory method usually adopt a laser canopy height distribution approach in which forest characteristics are predicted using measures such as percentiles of the distribution of laser canopy heights across a fixed area. The method requires a ground-truth sample of accurately measured field plots. One possibility for reducing the costs lies in the use of existing field plots for ground-truth purposes. The most obvious alternative in Finland would be to use truncated angle count sample plots of the National Forest Inventory or more locally data of checking of inventory by compartments. Due to the lack of suitable angle count ground-truth data and corresponding laser data, we tested this possibility using data on fixed-area sample plots, in which tree locations were simulated. The trees for a truncated angle count sample plot were then chosen and the resulting data together with the characteristics of an ALS-based canopy height distribution were used to construct regression models to predict stem volume, basal area, stem number, basal area median diameter and height. The accuracy of the stand attributes was found to be almost as good as in the case of models of fixed-area plots. © Institute of Chartered Foresters, 2006. All rights reserved.