JERS-1 SAR (合成開ロレーダ) 画像データによるブラジル中央アマゾニア地域の熱帯雨林の解析

抄録

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.