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Sökning: id:"swepub:oai:research.chalmers.se:d6014f25-4526-4946-a3a6-da64f278d1bc" > Spaceborne Syntheti...

Spaceborne Synthetic Aperture Radar for Sea Ice Observations, Concentration and Dynamics

Berg, Anders, 1983 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
 (creator_code:org_t)
ISBN 9789173859677
2014
Engelska.
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)
Abstract Ämnesord
Stäng  
  • Spaceborne Synthetic Aperture Radar (SAR) is the primary choice for sea ice monitoring due to its all-weather, day-and-night capability and regular delivery of high resolution images. This thesis presents methods for estimation of sea ice concentration and drift, a multi-sensor study of Baltic Sea ice radar signatures and an interferometric study of landfast sea ice. The ice concentration is determined by combining spatial autocorrelation and backscatter intensity in a neural network, which is trained with ice charts for the Baltic Sea. The root-mean-square error of the estimated concentration is found to be 7 percentage points for a spatially uniform distribution of ice concentrations. The ice drift is estimated from sequential SAR images by combining two methods: 1) areal matching by phase correlation, and 2) feature-based matching by detection and tracking of individual floes. The first method includes a module to resolve rotation. The second method is designed to assist tracking in the marginal ice zone and processes images in two steps: Firstly, by segmentation based on intensity thresholding to obtain objects corresponding to floes, and secondly, by feature tracking of floe outlines. A thresholding method that locates the antimode of imbalanced bimodal distributions is introduced, as well as a novel method for handling of aggregated floes. Assessment against manual measurements showed that up to 98% of drift vectors were estimated correctly, though the number varies with image pair and internal settings. Further, the ice drift algorithm is applied to C-band SAR images from a two-week spring period in the Fram Strait, and the measured ice drift is compared to drift modelled by the ice-ocean model HIROMB. The model is shown to overestimate the drift by a factor 1-2.5, attributable to an underestimated ice thickness, and to exhibit a 10°-30° offset in drift direction, independent of the drift direction.The thesis also evaluates the usefulness of spaceborne SAR sensors for ice charting. The traditionally employed C-band data is compared against X- and L-band data in terms of information content. It is found that L-band co-polarisation aids identification of ridge clusters and is less affected by microscale ice structures, whereas the information content in C- and X-band data is largely equivalent. Finally, interferometric acquisitions over landfast sea ice in the Bay of Bothnia demonstrate the capability of X-band SAR for small-scale deformation mapping of fast ice. Deformation occurs for example around leads, rocky islands and grounded ice ridges.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Rymd- och flygteknik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Aerospace Engineering (hsv//eng)
TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Fjärranalysteknik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Remote Sensing (hsv//eng)
NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)
NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)
TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Signalbehandling (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Signal Processing (hsv//eng)
NATURVETENSKAP  -- Data- och informationsvetenskap -- Datorseende och robotik (hsv//swe)
NATURAL SCIENCES  -- Computer and Information Sciences -- Computer Vision and Robotics (hsv//eng)
TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Nyckelord

synthetic aperture radar
interferometry
satellite
sea ice dynamics
sea ice monitoring
sea ice concentration

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vet (ämneskategori)

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