TOWARD CONSISTENT REGIONAL-TO-GLOBAL-SCALE VEGETATION CHARACTERIZATION USING ORBITAL SAR SYSTEMS

A study was conducted to assess the potential of combined imagery from the existing European and Japanese orbital synthetic aperture radar ( SAR) systems, ERS-1 (C-band, VV-polarization) and JERS-1 (L-band, HH-p olarization), for regional-to-global-scale vegetation classification. For seven test sites from various ecoregions in North and South Americ a, ERS-1/JERS-1 composites mere generated using high-resolution digita l elevation model (DEM) data for terrain correction of geometric and r adiometric distortions. An edge-preserving speckle reduction process w as applied to reduce the fading variance and prepare the data for an u nsupervised clustering of the two-dimensional (2-D) SAR feature space. Signature-based classification of the clusters was performed for all test sites with the same set of radar backscatter signatures, which we re measured from well-defined polygons throughout all test sites. Whil e trained on one-half of the polygons, the classification result was t ested against the other half of the total sample population. The multi site study was followed by a multitemporal study in one test site, cle arly showing the necessity of including multitemporal data beyond a le vel 1 (woody, herbaceous, mixed) vegetation characterization. Finally, classifications with simulation of backscatter variations shows the d ependence of the classification results on calibration accuracy and on naturally occurring backscatter changes of natural surfaces. Overall, it is demonstrated that the combination of existing orbital L- and C- band SAR data is quite powerful for structural vegetation characteriza tion.