Abstract
The general approach to inversion for a specific rough-surface parameter through average power measurements is to maximize the sensitivity of the return power to the parameter of interest and minimize its sensitivity to other surface parameters. This is usually achieved by an appropriate choice of coherent or incoherent measurements, polarization, look angle and frequency.
To invert for rms surface height, sensing wavelength should be large compared with the surface height and coherent measurements at normal incidence are usually made. To recover the surface-roughness spectrum or surface correlation, incoherent measurements should be made over a wide range of incidence angles at a sufficiently low frequency or frequencies and at vertical polarization. On the other hand, to determine the rms slope of a randomly rough surface, it is better to choose an exploring wavelength small compared with both the horizontal and vertical roughness scales. Incoherent measurements should be carried out over a range of angles near vertical incidence. The sensing of the average surface permittivity for a natural terrain is currently done at C-band with an incidence angle around 10± for slightly rough to very rough terrains.
For unknown surfaces which can only be studied with remote sensors, it is possible to determine their roughness scales relative to the incident wavelength by examining their angular scattering characteristics at both vertically and horizontally polarized states. In general, an angular backscattering curve with no polarization dependence indicates scattering by roughness scales larger than the incident wavelength. Over angular regions where vertical and horizontal returns are well separated the scattering must be dominated by roughness scales small compared with the wavelength.
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© 1985 D. Reidel Publishing Company
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Fung, A.K. (1985). Inverse Methods in Rough-Surface Scattering. In: Boerner, WM., et al. Inverse Methods in Electromagnetic Imaging. NATO ASI Series, vol 143. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-5271-3_12
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DOI: https://doi.org/10.1007/978-94-009-5271-3_12
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