Frequency dependence of polarization phase difference

Polarimetric AIRSAR data of 13 July 1990 acquired over Mahantango watershed area were processed for the identification of cornfields and forested areas. Polarization Phase Difference (PPD) values were computed for the cornfields at P-, L- and C- bands and studied as a function of frequency. The results compare well with the model calculations at 24° incidence angle, whereas the locations of cornfields were computed to be at 35° incidence angle. The discrepancy is attributed to a lack of accurate ground truth and the undulating topography of the cornfields. Another study reported here deals with the usefulness of the Polarization Index (PI) for the study of vegetation. PI was found to be dependent on the frequency for the cornfields, whereas for forest trees no such dependence was noticed. PI HH,HV is a more useful parameter than PI HH,HV even for the study of cornfields.