The use of airborne laser scanning to estimate sawlog volumes

This study of estimation of the sawlog volume of clear-cut stands from airborne laser scanning data considers both theoretical and factual recoveries. Theoretical sawlog volume estimates for the trees were calculated with a taper curve and factual estimates were obtained by multiplying the result by a model-based sawlog reduction factor, to allow for defects. Dominant tree species-specific models for the estimation of sawlog volumes per hectare were constructed with laser-based canopy height metrics as independent variables. The models were tested with the use of independently collected test data that consisted of 14 harvester-measured forest stands. Test data included information on the tapering of the stems and the volumes of the actually harvested assortments. The results indicate that the direct laser models are capable of producing satisfactory estimates for both the theoretical and the factual sawlog volumes of a clear-cut stand, with root mean squared errors of 9.1 and 18.0 per cent in the test data, respectively. In conclusion, the method presented here is quite suitable for pre-harvest estimation of sawlog volume, even though in cases where unpredictable defects (e.g. decay as a result of disease) exist the sawlog recoveries may be significantly overestimated.