A preliminary study on deforestation monitoring in Sumatra Island by PALSAR

An L-band normalized radar cross section (NRCS) characteristic derived from the Phased Array L-band Synthetic Aperture Radar (PALSAR) 50-m resolution dual-polarization mosaic and the land cover database in Riau province, Sumatra Island, represent that HV signals of natural forests are 2-3 dB larger than those of cleared and many plantations, indicating the usefulness of HV measurements for the detection of new deforestation. The 2007 and 2008 mosaic series, in fact, elucidates 3dB decreases in the HV channel for major deforested areas. On the other hand, HH shows no significant changes. 46-day repeat ScanSAR observations clarify common HH signal changes for the deforestation: they once increase departing from the annual cycle of natural forests and reach a peak in a rainy season. The result suggests the availability of the ScanSAR-derived HH time series for near-real-time deforestation monitoring. A HH signal variation on an acacia plantation cycle represents a similar characteristic to that for the deforestation: HH anomalously increases during the subsequent rainy season after the plantation. The increase level depends on an incidence angle, suggesting the dominance of surface scattering component over young acacia areas. With analogy with deforestations, it is suggested that the incidence angle dependency seems to be considered for the deforestation monitoring by ScanSAR.