A visual inspection of SIR-C SAR images (Figure 5) reveals that some discrimination between forested and non-forested areas is possible with L-HV and, to a lesser extent, with L-HH band and polarization combinations.
At C-band, neither polarizations appear to reveal tonal differences that might be helpful for this discrimination. This behavior may be related to the fact that the longer wavelength radar radiation (L-band) penetrates further into the vegetation canopy, and is thereby able to discriminate primary forest from other vegetation classes.
The dependence of microwave backscatter on total above-ground biomass has been documented in previous works for pine forests (Le Toan et al, 1992; Beaudoin et al, 1992), mixed deciduous and coniferous (Ranson et al, 1994, Rignot et al, 1994). All these studies show similar results, that can be summarized as:
In the forthcoming analysis the relationship between tropical forest regeneration stages and SIR-C SAR data (means and CV) is studied, and the discriminatory power of these measures is quantitatively assessed. Similar conclusions to those above are drawn from the current data.