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- Demchev, Denis, 1984, et al.
(författare)
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Alignment of Multi-Frequency SAR Images Acquired over Sea Ice Using Drift Compensation
- 2023
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Ingår i: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. - 2151-1535 .- 1939-1404. ; 16, s. 7393-7402
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the feasibility to align synthetic aperture radar (SAR) imagery based on a compensation for sea ice drift occurring between temporally shifted image acquisitions. The image alignment is a requirement for improving sea ice classification by combining multi-frequency SAR images acquired at different times. Images obtained at different radar frequencies provide complementary information, thus reducing ambiguities in the separation of ice types and the retrieval of sea ice parameters. For the alignment we use ice displacement vectors obtained from a sea ice drift retrieval algorithm based on pattern matching. The displacement vectors are organized on a triangular mesh and used for a piecewise affine transformation of the slave image onto the master image. In our case study we developed an alignment framework for pairs of ALOS-2 PALSAR-2 (L-band) and Sentinel-1 (C-band) images. We demonstrate several successful examples of alignment for time gaps ranging from a few hours to several days, depending on ice conditions. The data were acquired over three test sites in the Arctic: Belgica Bank, Fram Strait, and Lincoln Sea. We assess the quality of alignment using the structural similarity index (SSIM). From the displacement vectors, locations and extensions of patches of strong ice deformation are determined which allows to estimate the possible areal size of successful alignment over undeformed ice and a judgment of the expected quality for each image pair. The comprehensive assessment of hundreds of aligned L-C SAR pairs shows the potential of our method to work under various environmental conditions provided that the ice drift can be estimated reliably.
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- Eriksson, Leif, 1970, et al.
(författare)
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Alignment of L-and C-Band SAR Images for Enhanced Observations of Sea Ice
- 2022
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Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS). ; 2022-July, s. 3798-3801
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Konferensbidrag (refereegranskat)abstract
- This paper discusses the alignment of Synthetic Aperture Radar (SAR) image pairs with one image acquired at L-and the other at C-band. For our study we used data from ALOS-2 PALSAR-2 and Sentinel-1 taken over sea ice in the Fram Strait. The use of multifrequency SAR data is beneficial for sea ice characterization and classification because it combines the advantages of the frequency dependence of signal penetration depths and backscattering characteristics due to small-scale ice properties. For drifting sea ice, however, an immediate combination of image pairs acquired with a time gap is usually not possible. Such cases require to consider the effects of ice drift. In this study we investigate the possibility to compensate for sea ice drift for separation in acquisition time ranging from a few hours to several days. The first results are promising and suggest that alignment of SAR image pairs obtained at different frequencies is possible even for larger time gaps between acquisitions if drift and deformation can be estimated reliably.
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| 4. |
- Eriksson, Leif, 1970, et al.
(författare)
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Evaluation of multi-polarization SAR data at L-, C- and X-band for sea-ice monitoring in the Baltic Sea
- 2010
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Ingår i: Proceedings of the ESA Living Planet Symposium 2010, 28 June - 2 July 2010, Bergen, Norway. ; ESA SP-686
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- SAR data from the satellites ALOS, Envisat, Radarsat-2 and TerraSAR-X were compared in order to evaluate their usefulness for sea ice monitoring in the Baltic Sea. Different advantages and disadvantages were identified for the SAR systems and imaging modes. It has been shown that cross-polarized data improve the discrimination between sea-ice and open water. Another observation is that it is easier to identify ice ridges in L-band data than in images from shorter wavelengths. The information content of X- and C-band images is largely equivalent, whereas L-band data provide complementary information. L-band SAR also seems tobe less sensitive to wet snow cover on the ice.
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| 5. |
- Eriksson, Leif, 1970, et al.
(författare)
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Evaluation of new spaceborne SAR sensors for sea-ice monitoring in the Baltic Sea
- 2010
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Ingår i: Canadian journal of remote sensing. - : Informa UK Limited. - 0703-8992 .- 1712-7971. ; 36:1, s. S56-S73
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Tidskriftsartikel (refereegranskat)abstract
- In this study, synthetic aperture radar (SAR) data from the Advanced Land Observing Satellite (ALOS) and the Envisat, RADARSAT-2, and TerraSAR-X satellites were compared to evaluate their usefulness for sea-ice monitoring in the Baltic Sea. Radar signature characteristics at different frequencies, polarizations, and spatial resolutions are presented for three examples from 2009. C-band like-polarization data, which have been used for operational sea-ice mapping since the early 1990s, serve as a reference. Advantages and disadvantages were identified for the different SAR systems and imaging modes. One conclusion is that cross-polarized data improve the discrimination between sea ice and open water. Another observation is that it is easier to identify ice ridges in L-band data than in images from shorter wavelengths. The information content of X- and C-band images is largely equivalent, whereas L-band data provide complementary information. L-band SAR also seems to be less sensitive to wet snow cover on the ice.
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