Combining TanDEM-X and Landsat 8 data for improved mapping of forest biomass

In this study, we assess the potential of combining forest tree height derived from interferometric SAR data with satellite optical data for improving accuracy of forest stem volume mapping. Study site was located near the Hyytiälä forestry station in central Finland, with terrain representative of the boreal coniferous forest. As a primary interferometric data, several data takes of TanDEM-X data are used. Satellite optical data were represented by Landsat 8 image. The ground reference data were information on stand level from forest management plans. Firstly, forest tree height is estimated from TanDEM-X interferometric SAR coherency. Further, retrieved tree heights are combined with optical data for predicting forest stem volume using linear regression framework. Results of regression analysis performed demonstrate considerable improvement in terms of obtained accuracy figures of the combined stem volume estimation (RMSE=34%, R²=0.57) compared with use of optical satellite data only (RMSE=40%, R²=0.43).