Revista Brasileira de Cartografia (Dec 2009)
Padrões de Respostas Polarimétricas SAR e Mecanismos de Espalhamento de Alvos Florestais Derivados de Radar de Banda L
Abstract
The objective of this study is to analyze the polarization responses derived from the airborne sensor SAR R99-B data (L-band) in areas of primary forest, secondary successions and forest with timber exploitation and those under recovery after a burning. In addition, we perform an exploratory analysis of the scattering mechanisms of each forest typology using an alternative procedure for SAR image classification based on target decomposition. The study site is located in the Tapajós region, Pará State (Brazil). Polarization response graphs were obtained by plotting the normalized cross-section of the forest targets, on a three-dimensional surface plot as a function of the orientation and ellipticity angles. The resulting surfaces were visually compared and the configuration of each plot was analyzed with support of physiognomic-structural information collected during forest inventories. The distinction between single and multiple scattering mechanisms was done by the association of entropy and alpha angle values derived from target decomposition for each sample area. Some results can be mentioned: (a) compared to areas of secondary succession, primary forests tend to present polarization responses with a higher pedestal, indicating greater variability in terms of scattering mechanisms; (b) for all thematic classes investigated, the distribution of pixels in the entropy-alpha angle classification space was more frequent at zones 4, 5 and 6, indicating the predominance of scattering processes with medium entropy. This study improves the understanding of the interaction mechanisms between L-band SAR signals and structural parameters of tropical rainforest, supporting inventory and the monitoring of forest in the Amazon region.
