Estimation of forest parameters using CARABAS-II VHFSAR data

The use of airborne CARABAS-II VHF (20-90 MHz) SAR data for retrieval of fo rest parameters has been investigated, The investigation was performed at a test site located in the southwest: of Sweden consisting mainly of Norway spruce forests. Regression models predicting forest parameters from radar b ackscattering amplitude were developed and evaluated. The results showed a linear relationship between backscattering amplitude and forest stem volume , stem diameter, and tree height. The analysis also showed that the radar s ignal is strongly affected by ground slope conditions. The root mean square errors from the regression analysis, restricted to forest stands on near-h orizontal ground, were found to be 66 m(3) ha(-1), 3.2 cm, and 2.3 m for st em volume, stem diameter, and tree height respectively. No saturation of th e backscattered signal was observed up to the maximum stem volume of 625 m( 3) ha(-1), corresponding to a biomass of 375 tons ha(-1). The results imply that VHF SAR data have significant potential for operational use in forest ry.