The usefulness of SAR data for the extraction of biophysical parameters is most dependent on frequency. Microwaves at lower frequencies such as L-band (2.0-1.0 GHz) and P-band (1.0-0.3 GHz) are better able to penetrate the canopy and interact more extensively with its structural components (leaves, branches, trunks). Microwaves at higher frequencies (C-band, 3.8 - 7.5GHz) tend to interact primarily with the upper portion of the canopy. The sensors at higher frequency therefore have a more limited potential use in the discrimination of variations in dry biomass whereas it is expected that L-band data and P-Band data can be used to discriminate increasing biomass variations.
9.3.2 Polarization Dependence
Le Toan et al., 1992 showed that the dynamic range of backscatter over uniform pine stands had a strong variation with polarization e.g., the dynamic range for such data obtained at P-band for the HV polarization was approximately 15 dB, at HH approximately 11 dB, and at VV approximately 4.8 dB. At L-band, the dynamic range was reduced , with a dynamic range of approximately 8.6 dB at HV, approximately 5.3 dB at HH and approximately 4.6 dB at VV. At C-band the dynamic range was significantly lower, with data for the HV polarization showing the greatest range (approximately 4 dB) and those in HH and VV polarizations showing a dynamic range of only 2dB.
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