Prediction of Plot - Level Forest Variables Using TerraSAR - X Stereo SAR Data

12 Promising results have been obtained in recent years in the use of high-resolution X-band stereo SAR 13 satellite images (with the spatial resolution being in order of meters) in the extraction of elevation 14 data. In the case of forested areas, the extracted elevation values appear to be somewhere between 15 the ground surface and the top of the canopy, depending on the forest characteristics. If the ground 16 surface elevations are known by using a Digital Terrain Model derived from Airborne Laser Scanning 17 surveys, it is possible to obtain information related to forest resources. To the best of our 18 knowledge, this paper, presents the first attempt to obtain forest variables at plot level based on 19 TerraSAR-X stereo SAR images (non-interferometric data). The study set consisted of 109 circular 20 test plots for which forest variables were observed by performing tree-specific measurements. The 21 statistical features were calculated for each test plot from the elevation values extracted from stereo 22 SAR data. This was followed by predicting field-observed plot-level forest variables from the features 23 derived from stereo SAR data using the Nearest Neighbors approach which employs the Random 24 Forest technique in selection of the nearest neighbors. The relative errors (RMSE%) for predicting 25 *Manuscript