A semi-empirical backscattering model at L-band and C-band for asoybean canopy with soil moisture inversion |
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Authors: | de Roo RD Yang Du Ulaby FT Dobson MC |
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Affiliation: | Dept. of Electr. Eng. & Comput. Sci., Michigan Univ., Ann Arbor, MI; |
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Abstract: | Radar backscatter measurements of a pair of adjacent soybean fields at L-band and C-band are reported. These measurements, which are fully polarimetric, took place over the entire growing season of 1996. To reduce the data acquisition burden, these measurements were restricted to 45° in elevation and to 45° in azimuth with respect to the row direction. Using the first order radiative transfer solution as a form for the model of the data, four parameters were extracted from the data for each frequency/polarization channel to provide a least squares fit to the model. For inversion, particular channel combinations were regressed against the soil moisture and area density of vegetation water mass. Using L-band cross-polarization and VV-polarization, the vegetation water mass can be regressed with an R 2=0.867 and a root mean square error (RMSE) of 0.0678 kg/m 2. Similarly, while a number of channels, or combinations of channels, can be used to invert for soil moisture, the best combination observed, namely, L-band VV-polarization, C-band HV- and VV-polarizations, can achieve a regression coefficient of R2=0.898 and volumetric soil moisture RMSE of 1.75% |
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