2.1 Parameters affecting soil moisture retrieval
2.1.1 Frequency or wavelength
The frequency of incident radiation has a direct
relationship with the penetration depth in the surface.
The L and C bandwidths are the most commonly used
wavelengths for soil moisture estimation. The longer
wavelengths (L-band) penetrate deeper in the soil
surface and/or vegetation canopy. L-band SAR sensor
is able to penetrate leaves and small branches and can
interact with tree trunks and branches as well as the
soil surface. In sparse vegetation, L band interacts
more with underlying surface rather than vegetation,
reducing its sensitivity to vegetation [20, 21].