Investigation of Tropical Rain Forest in Central Amazonia, Brazil based on JERS-1 SAR Images

Abstract

Taking advantage of capability of SAR (Synthetic Aperture Radar) on board Japanese earth observation satellite, JERS-1, which can observe ground condition through clouds, an attempt is made to investigate of tropical rain forests in two sites in Central Amazonia, Brazil. The first site extends from 0.5 S to 5.5 S and from 59 W to 65 W and the second site is a smaller area of about 75 km×150km located to the south of the first site.Since the coverage of 1 scene of SAR image is approximately 75 km×80km, it is necessary to mosaic 90 scenes of SAR images for the first site and 2 scenes of SAR images for the second site respectively. A practical scheme of processing a large amount of SAR image data is developed.Through the analyses of the mosaic images following features are found. The tropical rain forest is well conserved in the first site while a fairly lage deforestation is found in the second site. The estimated deforested area from SAR images is at least 607.1 km2 on October 27 1992 and 661.5 km2 on June 4 1993 in Sena Madureira, while in Rondonia it is estimated that at least forest of 302.7 km2 was newly cut down between July 19 1992 and April 9 1993 and the deforested area is at least 4, 629.0 km2 on October 2 1993. It is also found that features of river system under the continuous coverage of tree layer can be detected.As the typical values of σ° (differential scattering coefficient, which is the average value of the scattering cross-section per unit area) following values are obtained. (1) Dense forest -10.88-5.96dB, (2) Forest in wet lands (or flooded land) -7.67-2.48 dB, (3) Deforestedarea -15.24-8.68 dB, (4) Shrubs/short trees in sterile soils called “campinarana” -17.87-8.16dB.