A production line for forest stem volume measurements from VHF SAR data

Retrieval of forest stem volume has been the main civilian application investigated for VHF SAR data during recent years. Based on promising results obtained from previous studies, a project was defined with the objective to develop a fully integrated system for retrieval of stem volume at high spatial resolution from CARABAS-II VHF SAR images. Using the developed production line, stem volume can easily be retrieved within predefined forest stands or within homogeneous areas defined by segmentation of optical satellite images. In order to evaluate the accuracy and efficiency of the production line, CARABAS-II images have been collected and analyzed over a test area covering 25×25 km². The major part of the area is owned by the Swedish forest company Holmen Skog AB. For coniferous forest stands, exhibiting normal forest production conditions, the accuracy in terms of root mean square error (RMSE) for estimation of forest stem volume is about 44 m³ ha^-1 (22% of the average stem volume) in the range of 70-400 m³ ha^-1, using the developed production line. In comparison to earlier research tools, the developed production line speeds up the analyses approximately 10 times.