Wetland characterization using polarimetric RADARSAT-2 capability

Abstract

The use of single-polarization (HH) RADARSAT-1 synthetic aperture radar (SAR) data has been shown to be important for wetland water extent characterization. However, the limited capability of the RADARSAT-1 single-polarization C-band SAR in vegetation type discrimination makes the use of clear-sky-dependent visible near-infrared (VNIR) satellite data necessary for wetland mapping. In this paper, the potential of polarimetric RADARSAT-2 data for wetland characterization is investigated. The Touzi incoherent decomposition is applied for the roll-invariant decomposition of wetland scattering. In contrast with the Cloude-Pottier decomposition that characterizes target scattering type with a real entity, α, the Touzi decomposition uses a complex entity, the symmetric scattering type, for unambiguous characterization of wetland target scattering. It is shown that, like the Cloude α scattering type, the magnitude αs of the symmetric scattering is not effective for vegetation type discrimination. The phase ϕαs of the symmetric scattering type has to be used for better characterization of wetland vegetation species. The unique information provided by ϕαs for an improved wetland class discrimination is demonstrated using Convair-580 polarimetric C-band SAR data collected over the Mer Bleue wetland in the east of Ottawa, Canada. The use of ϕαs makes possible the discrimination of shrub bog from sedge fen and even permits the discrimination between conifer-dominated treed bog and upland deciduous forest under leafy conditions.