Ku BAND POLARIZATION CHARACTERISTICS OF CROPS
Hinds, Mark Richards
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A frequency modulated, continuous wave Ku-band, ground based scatterometer was modified into a full polarimeter for measurement of the back-scattered polarization characteristics of crops and soils. This thesis starts with a summary of important topics in radar, fading, and polarization theory applied to the Canadian Centre for Remote Sensing / (CCRS) Ground Microwave Operations (GMO) Ku-band Polarimeter. Once the polarimeter hardware is described, then the 1987 GMO polarimeter experiment on the polarization characteristics of spring wheat, durum wheat, barley, and canola is discussed. To properly evaluate this polarimeter data set, the analysis section considers the statistical independence and processing of the six, sequentially scanned, polarimeter intensity measurements. These six intensity measurements are partially dependent, but they are considered to be independent, for the purposes of calculating the estimated averages and variances of the polarization state parameters (the ellipse angles: &, orientation angle and x, the ellipticity angle; and m,the polarization ratio). The calculated polarization state parameters are displayed, graphically, for qualitative evaluation of the change in the received polarization state from that transmitted, for the four different crops under a variety of measurement conditions (transmit polarization, incidence angle, time [days during the growing season], range cell, row aspect angle, and planting conditions. From a review of the data, crop canopies primarily unpolarize the incident Ku-band polarized radiation, with no consistent depolarization effects observed. The crops display significantly different unpolarization signatures (from 3-D graphs of the polarization ratio) as a function of transmit polarization, incidence angle and time: • wheat, durum and barley (all cereal crops) exhibit significant unpolarization for vertical linear transmit polarization, but minimal unpolarization for horizontal linear transmit polarization; • canola exhibits similar unpolarization signatures for both linear transmit polarization states. The three cereal crops can be distinguished from canola , but wheat, durum, and barley can not be clearly distinguished among each other. The stronger interaction of the cereal crops with the vertical transmit polarization state confirms earlier work on the importance of e vii  in attenuation studies of wheat. Further, the polarization characteristics of canola indicate a much different, less orientation dependent scattering process. Finally the predominence of unpolarization in the canopy scattering process indicates that the cross polarization measurements done in scatterometer studies are primarily unpolarized power measurements.