Análise multitemporal das mudanças radiométricas em imagens de satélite de bordas de foresta para inferir áreas de corte seletivo na foresta Amazônica

Abstract

Radiometric changes observed in multi-temporal optical satellite images have an important role in efforts to characterize selective-logging areas. Te aim of this study was to analyze the multi-temporal behavior of spectral-mixture responses in satellite images in simulated selective-logging areas in the Amazon forest, considering red/near-infrared spectral relationships. Forest edges were used to infer the selective-logging infrastructure using differently oriented edges in the transition between forest and deforested areas in satellite images. TM/Landsat-5 images acquired at three dates with different solar-illumination geometries were used in this analysis. Te method assumed that the radiometric responses between forest with selective-logging effects and forest edges in contact with recent clear-cuts are related. Te spatial frequency attributes of red/near infrared bands for edge areas were analyzed. Analysis of dispersion diagrams showed two groups of pixels that represent selective-logging areas. Te attributes for size and radiometric distance representing these two groups were related to solar-elevation angle. Te results suggest that detection of timber exploitation areas is limited because of the complexity of the selective-logging radiometric response. Thus, the accuracy of detecting selective logging can be influenced by the solar-elevation angle at the time of image acquisition. We conclude that images with lower solar-elevation angles are less reliable for delineation of selecting logging.