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Fitting a two-component scattering model to polarimetric SAR data from forests

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dc.contributor.author Freeman, Anthony
dc.date.accessioned 2008-11-06T15:43:22Z
dc.date.available 2008-11-06T15:43:22Z
dc.date.issued 2007-08
dc.identifier.citation IEEE Transactions on Geoscience And Remote Sensing, Vol. 45, No. 8, p. 2583-2592, August 2007 doi 10.1109/TGRS.2007.897929 en_US
dc.identifier.clearanceno 06-3761
dc.identifier.uri http://hdl.handle.net/2014/41005
dc.description.abstract Two simple scattering mechanisms are fitted to polarimetric synthetic aperture radar (SAR) observations of forests. The mechanisms are canopy scatter from a reciprocal medium with azimuthal symmetry and a ground scatter term that can represent double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants or Bragg scatter from a moderately rough surface, which is seen through a layer of vertically oriented scatterers. The model is shown to represent the behavior of polarimetric backscatter from a tropical forest and two temperate forest sites by applying it to data from the National Aeronautic and Space Agency/Jet Propulsion Laboratory's Airborne SAR (AIRSAR) system. Scattering contributions from the two basic scattering mechanisms are estimated for clusters of pixels in polarimetric SAR images. The solution involves the estimation of four parameters from four separate equations. This model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem. The model is used to develop an understanding of the ground-trunk double-bounce scattering that is present in the data, which is seen to vary considerably as a function of incidence angle. Two parameters in the model fit appear to exhibit sensitivity to vegetation canopy structure, which is worth further exploration. Results from the model fit for the ground scattering term are compared with estimates from a forward model and shown to be in good agreement. The behavior of the scattering from the ground-trunk interaction is consistent with the presence of a pseudo-Brewster angle effect for the air-trunk scattering interface. If the Brewster angle is known, it is possible to directly estimate the real part of the dielectric constant of the trunks, a key variable in forward modeling of backscatter from forests. It is also shown how, with a priori knowledge of the forest height, an estimate for the attenuation coefficient of the canopy can be obtained directly from the multi-incidence-angle polarimetric observations. This attenuation coefficient is another key variable in forward models and is generally related to the canopy density. en_US
dc.description.sponsorship NASA/JPL en_US
dc.language.iso en_US en_US
dc.publisher IEEE en_US
dc.subject polarimetry en_US
dc.subject scattering mechanisms en_US
dc.subject synthetic aperture radar (SAR) en_US
dc.subject tropical forests en_US
dc.subject temperate forests en_US
dc.title Fitting a two-component scattering model to polarimetric SAR data from forests en_US
dc.type Article en_US


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