Laser-scanning for the Derivation of Forest Stand Parameters

Forest stand parameters are derived from airborne laser scanner data. Data from three laser scanner flights by the company "TopoSys" are used, a winter flight with last pulse recorded and two summer flights, with last and first pulse recorded respectively. The laser data are reduced to relative (ground) heights with a high quality ground elevation model (DEM) that was interpolated from the winter data. The proportion of crown coverage of coniferous trees are estimated from data for 50 stands. Stand heights and basal area proportion of coniferous versus deciduous trees are estimated through regression analysis against terrestrial reference data from 110 angle count points, each with approximatly 10 trees. The results are very promising with regression coefficients of 0.8 to 0.95 for all measures. The usual systematic under-estimation of tree heights cannot be proved due to the high sample point density. The mean errors of the tree heights are in the range of ±1.8 – ±2.7 m. Basal and projected crown area proportions can be estimated with similar precision. Summer last and first pulse elevations differ insignificantly, suggesting there is no need to have both flights. Only one winter flight is necessary.