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TitlePhase of target scattering for wetland characterization using polarimetric C-band SAR
AuthorTouzi, R T; Deschamps, A D; Rother, G R
SourceIEEE Transactions on Geoscience and Remote Sensing (Institute of Electrical and Electronics Engineers) vol. 47, issue 9, 2009 p. 3241-3261,
Alt SeriesEarth Sciences Sector, Contribution Series 20090207
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Mediapaper; on-line; digital
File formatpdf
NTS31G/05; 31G/06
AreaOttawa; Mer Bleue
Subjectsgeophysics; Science and Technology; Nature and Environment; remote sensing; satellite imagery; radar imagery; radar methods; wetlands; bogs; fens; change detection; synthetic aperture radar surveys (SAR); Classification; Methodology
ProgramRemote Sensing Science
Released2009 06 05
AbstractWetlands continue to be under threat, and there is a major need for mapping and monitoring wetlands for better management and protection of these sensitive areas. Only a few studies have been published on wetland characterization using polarimetric synthetic aperture radars (SARs). The most successful results have been obtained using the phase difference between HH and VV polarizations, phi HH - phi VV , which has shown promise for separating flooded wetland classes. Recently, we have introduced a new decomposition, the Touzi decomposition, which describes target scattering type in terms of a complex entity, the symmetric scattering type. Huynen's target helicity is used to assess the symmetric nature of target scattering. In this paper, the new complex-scattering-type parameters, the magnitude alpha s and phase Phi alpha s , are investigated for wetland characterization. The use of the dominant-scattering-type phase Phi alpha s makes it possible to discriminate shrub bogs from poor (sedge or shrub) fens. These two classes cannot be separated using phi HH - phi VV , or the radiometric scattering information provided by alpha s , the Cloude alpha, the entropy H , and the multipolarization HH-HV-VV channels. phi alpha s , which cannot detect deep (45 cm below the peat surface) water flow in a bog, is more sensitive to the shallower (10-20-cm) fen beneath water, and this makes possible the separation of poor fens from shrub bogs. Phi alpha s also permits the discrimination of conifer-dominated treed bog from upland deciduous forest under leafy conditions. Target helicity information is exploited to introduce a new parameter, the target asymmetry. The latter is shown very promising for detection of forest changes between leafy and no-leaf conditions. The analysis of low-entropy marsh scattering showed that both the scattering-type magnitude and phase alpha s and Phi alpha s , respectively, as well as the maximum polarization intensity of the dominant scattering m , are needed for a better understanding of marsh complex scattering mechanisms. The unique information provided by the new roll-invariant decomposition parameters are demonstrated using repeat-pass Convair-580 polarimetric C-band SAR data collected in June and October 1995 over the RAMSAR Mer Bleue wetland site near Ottawa (Canada).

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