Abstract
The transmittance of laser beams for different thinning intensities and the effects of sampling density on the estimation of stand density and tree height in the airborne laser scanner measurement of a Cryptomeria japonica stand were investigated. The transmittance of laser beams in plots of heavy thinning, light thinning and no thinning, which affected the accuracy of DEM (digital elevation model), were 95.8%, 86.5%, and 75.2% respectively. The extraction rates of standing trees from DCM (digital canopy model) in 0.25 meter meshes, which were derived from airborne laser scanner data, were 28.1%, 26.8% and 21.3% in plots of heavy thinning, light thinning and no thinning, respectively. The correlation coefficient between tree height derived from DCM and that derived from the field survey was 0.92. The rate of extraction of standing trees from DCM declined suddenly when the sampling density was below 3-5 points/m^2. The mean difference between tree heights derived from DCM with high sampling density and one with low sampling density was 0.5-0.6 meter and the height was underestimated by the low sampling density beams.
