The effect of soil and crop residue characteristics on polarimetric radar response

Although the interaction between linear polarized microwaves and agricultural targets has been studied extensively, far less is understood about the added information provided from polarimetric Synthetic Aperture Radars (SARs). Using 1994 Spaceborne Imaging Radar-C (SIR-C) data, this study examines the sensitivity of linear polarizations and polarimetric parameters to conditions present on agricultural fields during the period of preplanting and postharvest. The polarimetric parameters investigated include circular polarized backscatter, pedestal height, and co-polarized phase differences (PPD). The co-polarizations signature plots are also discussed. Results indicate that the dominant scattering mechanism from these fields varies depending on the type and amount of residue cover, and whether the crop had been harvested. Radar parameters most sensitive to volume and multiple scattering perform best at characterizing these surface conditions. These parameters are the pedestal height, as well as the linear cross-polarization (HV) and the circular co-polarizations (RR). The co-polarizations signature plots and the standard deviation associated with the PPD are also useful in categorizing these cover types. However, the field average PPD provides little information on residue and soil characteristics.