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TitleEvaluating cimulated RADARSAT constellation mission (RCM) compact polarimetry for open-water and flooded-vegetation wetland mapping
AuthorOlthof, I; Rainville, T
SourceRemote Sensing vol. 12, issue 9, 1476, 2020 p. 1-29, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200081
PublisherMDPI AG
Mediapaper; on-line; digital
File formatpdf; html
Subjectsgeophysics; hydrogeology; environmental geology; Science and Technology; Nature and Environment; Health and Safety; wetlands; floods; flood plains; mapping techniques; remote sensing; satellite imagery; radar methods; vegetation; surface waters; Emergency Geomatics Service; Radarsat-2; Radarsat Constellation Mission (RCM); Emergency services; monitoring; synthetic aperture radar surveys (SAR); Methodology
Illustrationssketch maps; flow diagrams; tables; plots; satellite images; aerial photographs
Released2020 05 06
AbstractWhen severe flooding occurs in Canada, the Emergency Geomatics Service (EGS) is tasked with creating and disseminating maps that depict flood extents in near real time. EGS flood mapping methods were created with efficiency and robustness in mind, to allow maps to be published quickly, and therefore have the potential to generate high-repeat water products that can enhance frequent wetland monitoring. The predominant imagery currently used is synthetic aperture radar (SAR) from RADARSAT-2 (R2). With the commissioning phase of the RADARSAT Constellation Mission (RCM) complete, the EGS is adapting its methods for use with this new source of SAR data. The introduction of RCM's circular-transmit linear-receive (CTLR) beam mode provides the option to exploit compact polarimetric (CP) information not previously available with R2. The aim of this study was to determine the most effective CP parameters for use in mapping open water and flooded vegetation, using current EGS methodologies, and compare these products to those created by using R2 data. Nineteen quad-polarization R2 scenes selected from three regions containing wetlands prone to springtime flooding were used to create reference flood maps, using existing EGS tools. These scenes were then used to simulate 22 RCM CP parameters at different noise floors and spatial resolutions representative of the three RCM beam modes. Using multiple criteria, CP parameters were ranked in order of importance and entered into a stepwise classification procedure, for evaluation against reference R2 products. The top four CP parameters-m-chi-volume or m-delta-volume, RR intensity, Shannon Entropy intensity (SEi), and RV intensity-achieved a maximum agreement with baseline R2 products of upward of 98% across all 19 scenes and three beam modes. Separability analyses between flooded vegetation and other land-cover classes identified four candidate CP parameters-RH intensity, RR intensity, SEi, and the first Stokes parameter (SV0)-suitable for flooded-vegetation-region growing. Flooded-vegetation-region-growing CP thresholds were found to be dependent on incidence angle for each of these four parameters. After region growing using each of the four candidate CP parameters, RH intensity was deemed best to map flooded vegetation, based on our evaluations. The results of the study suggest a set of suitable CP parameters to generate flood maps from RCM data, using current EGS methodologies that must be validated further as real RCM data become available.

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