Abstract
The aim of this study was to exploit fully polarimetric SAR data acquired during TanDEM-X – Science Phase (2014/2015) over herbaceous wetlands of the Biebrza National Park (BbNP) in North-Eastern Poland for mapping seasonally flooded grasslands and permanent natural vegetation associations. The main goal of this work was to estimate the advantage of fully polarimetric radar images (QuadPol) versus alternative polarization (AltPol) modes. The methodology consisted in processing of several data subsets through polarimetric decompositions of complex quad-pol datasets, classification of multitemporal backscattering images, complementing backscattering images with Shannon Entropy, exploitation of interferometric coherence from tandem operations. In each case the multidimensional stack of images has been classified using ISODATA unsupervised clustering algorithm. With 6 QUAD-POL TSX/TDX acquisitions it was possible to distinguish correctly 5 thematic classes related to their water regime: permanent water bodies, temporarily flooded areas, wet grasslands, dry grasslands and common reed. This last category was possible to distinguish from deciduous forest only with Yamaguchi 4 component decomposition. The interferometric coherence calculated for tandem pairs turned out not so efficient as expected for this wetland mapping.
Highlights
The hundreds of scientific papers, reports and books have been published on remote sensing of wetlands since decades
The methodology consisted in processing of several data subsets, their thematic classifications and accuracy assessment as follows: - polarimetric decompositions and classifications of complex quad-pol datasets, - classification of multitemporal backscattering images, - complementing backscattering images with Shannon Entropy parameter possible to retrieve in dual-pol mode (Single Receive Antenna), - exploitation of interferometric coherence between two images acquired during tandem operations
With 6 QUAD-POL TSX/TDX acquisitions it was possible to distinguish correctly 5 thematic classes related to their water regime: permanent water bodies, temporarily flooded areas, wet grasslands, dry grasslands and common reed
Summary
The hundreds of scientific papers, reports and books have been published on remote sensing of wetlands since decades. The last decades microwave (radar) technologies became largely exploited in wetland remote sensing due to their all-weather imaging ability and sensibility to specific features of the wetlands i.g. vegetation structure (types, species, biomass,...), water content in soils and plants, surface roughness determined by vegetal cover. The differences in imaging angles have been exploited as factors having influence on the penetration depth in vegetal cover and in consequence on scattering mechanisms proportions. Another interesting aspect of flooded vegetation mapping with SAR is interferometric coherence (Hong & Wdowinski 2015). The achieved results of mapping and/or monitoring based on classification of the multitemporal stack of
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