On the use of Radarsat and JERS-1 satellite SARs for trail and road detection in tropical rainforests

The basic imaging geometry of the SAR is considered for the study of trail and road detectability in rainforests with no significant topographic relief, as a function of the SAR parameters and trail (or road) shape. It is shown that the visibility of these features on SAR images depends mainly on the SAR resolution, trail (or road) width and their orientation relative to the SAR viewing direction. The results are confirmed experimentally on a dense forest site in the south of Sumatra, Indonesia, using the multi-resolution capability of Radarsat. The best trail detectability was obtained with the fine modes at the highest incidence angle. The use of both ascending and descending fine modes permit even the detection of 5 to 6 m width trails under particular conditions. The same trails could not be detected using JERS-1 satellite SAR of coarser resolution. The resolution dominates trail detectability and the use of a longer wavelength (L-band for JERS-1) does not allow to resolve narrow trails