II. DATA AND STUDY AREA
We use a reduced data set extracted from two GRFM mosaics
of JERS-1 SAR images covering the entire Central Africa
[16], [13]. The acquisition dates of the images, February and
November 1996, correspond to the high and low water seasons
of the Congo River respectively. The GRFM Africa mosaics are
derived from Level 2.1 NASDA high resolution and georeferenced
JERS-1 products (3-look, 12.5 m pixel spacing in both
azimuth and range). In this study,we use the Africa mosaic baseline
product with 100 meter resolution [13], [8]. The 100 m amplitude
backscatter images were generated by low-pass filtering
and decimation from the high resolution NASDA products. The
downsampling process is based on a multiresolution decomposition
where the scaling function is a cubic spline polynomial.