Comparison of SAR and optical images of the rainforests of Borneo, Malaysia with field data

Preliminary results are described on the comparison of the optical and radar images of the rainforests of Sarawak, Malaysia, with the ground-truth data collected from the field survey. The test sites are the mangrove and adjacent virgin forests, and oil-palm plantation areas. Visible and infrared images acquired by the MOS-1b have shown their capability of extracting deforestation areas, but their applications to mangrove forests are limited. Operating at L-band with longer penetration depth, the JERS-1 SAR is superior to the ERS-2 C-band SAR for differentiating the mangrove from virgin forests, although both forests have biomass similar and well above the saturation range of the L-band RCS. The field data show that the mean tree diameter is about a half the radar wavelength in both the forests, indicating that the L-band microwave is "semi-transparent" in these forests. It is, thus, concluded that the lower (about 6 dB) RCS in the mangrove is due to specular reflection beneath the forests; while in the virgin forests there is a substantial amount of diffuse scattering by undergrowth. This hypothesis is supported by the difference in image intensity between the dry and wet seasons.