| 1. |
- Berg, Anders, 1983, et al.
(author)
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X-Band Interferometric SAR Observations of Baltic Fast Ice
- 2015
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In: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892 .- 1558-0644. ; 53:3, s. 1248-1256
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Journal article (peer-reviewed)abstract
- Detailed mapping of fast-ice deformation can be used to characterize the rheological behavior of fast ice and subsequently improve sea ice modeling. This study uses interferometric synthetic aperture radar to map fast-ice deformation with unprecedented spatial resolution (meter range) and sensitivity (cm-mm range). Two interferometric acquisitions, each with a temporal baseline of 24 h, were performed by the X-band SAR satellite constellation Cosmo-SkyMed over the northeast Bay of Bothnia in the middle of the 2012 ice season. The first interferogram shows deformation of the fast ice due to force from impinging drift ice, and the normal strain within the fast ice is measured. Complementary intensity correlation measurements reveal a slow movement of the drift ice toward the fast ice. The second interferogram exhibits a low fringe rate over the fast ice with fringes being aligned along the coastline. Deformation appears to be stronger around leads, skerries, and grounded ice ridges. It is also observed that the coherence images provide information that is complementary to the information in the backscatter images.
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| 2. |
- Berg, Anders, 1983, et al.
(author)
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Demonstration of X-Band SAR Interferometry over Baltic Fast Ice
- 2013
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In: Proceedings of Earth Observation and Cryosphere Science, 13 - 16 November 2012, Frascati, Italy. - 1609-042X. - 9789290922766 ; 2013
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Conference paper (other academic/artistic)abstract
- This study utilizes X-band SAR images acquired by theCosmo-SkyMed satellite constellation to map fast icedeformation at high spatial resolution. Twointerferometric acquisitions were performed in themiddle of the ice season in 2012 and with a temporalbaseline of 24 hours. The first interferogram revealsdeformation of the fast ice which is being forced by theramming drift ice. The drift ice moved towards the fastice with up to 600 m based on phase correlationmeasurements. The second interferogram shows a ratherlow fringe rate over the fast ice with fringes beingaligned along the coastline. Emerging cracks are easilyidentified with the associated phase discontinuities. It isalso observed that the backscatter and coherence levelsare connected in certain regions.
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| 3. |
- Berg, Anders, 1983, et al.
(author)
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Evaluation of a sea ice algorithm for SAR data from the Bay of Bothnia
- 2010
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In: Proceedings of the Third International Workshop SeaSAR 2010, 25-29 January 2010, Frascati, Italy. - 1609-042X. - 9789292212438 ; ESA SP-679
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Conference paper (other academic/artistic)abstract
- A sea ice drift algorithm published by M. Thomas et. al.(2008) has been implemented and evaluated. Input tothe algorithm is Synthetic Aperture Radar (SAR)images, which are processed using phase correlation ina multi-resolution processing system. The algorithm hasbeen tested with horizontally co-polarized (HH)ENVISAT ASAR Wide Swath images andRADARSAT-2 ScanSAR images. The possible benefitsof using cross-polarized (HV) RADARSAT-2 ScanSARdata are investigated, and initial testing of the algorithmfor L-band SAR data from ALOS PALSAR has beendone.The validity of the produced motion fields has beentested in three different ways. Most of the SAR imagesin this analysis were acquired over the Bay of Bothnia.Five meteorological stations located in this region havebeen collecting wind data with a temporal resolution ofthree hours. It is confirmed that the wind data correlateswith the derived sea ice motion. Another source ofvalidation data that has been used is the daily ice chartspublished by the Swedish Meteorological andHydrological Institute (SMHI). The third method usedfor validation is straightforward, visual tracking of seaice features.The algorithm is facing some difficulties when it comesto ice tracking close to the shoreline, in archipelagoesetc, since the motionless solution will be favoured. Itcan however be suppressed by filtering areas of land.This addition gives a more robust algorithm.
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| 4. |
- Berg, Anders, 1983, et al.
(author)
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Evaluation of sea ice concentration algorithm for SAR data from the Bay of Bothnia
- 2010
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In: Proceedings of the ESA Living Planet Symposium 2010, 28 June - 2 July 2010, Bergen, Norway.
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Conference paper (other academic/artistic)abstract
- A sea ice coverage algorithm has been developed for C-band SAR data. It has been tested with images from ENVISAT ASAR in Wide Swath Mode (WSM) over the Bay of Bothnia and the Svalbard region. The algorithm is based on autocorrelation in combination with Otsu’s thresholding method. Ice charts over the Bay of Bothnia have been used for a qualitative validation of the results.
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| 5. |
- Berg, Anders, 1983, et al.
(author)
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SAR Algorithm for Sea Ice Concentration - Evaluation for the Baltic Sea
- 2012
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In: IEEE Geoscience and Remote Sensing Letters. - 1558-0571 .- 1545-598X. ; 9:5, s. 938 - 942
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Journal article (peer-reviewed)abstract
- A new sea ice concentration algorithm has been developed for C-band synthetic aperture radar data. Detailed autocorrelation statistics are derived and adopted by the algorithm, and a neural network is utilized for training against 41 sea ice charts. The charts are produced by ice analysts at the Swedish Ice Service and cover the Baltic Sea. The classification of open water pixels is accurate to 94% on average, and the classification of sea ice pixels has an accuracy of 87%. This results in a root-mean-square error of 6.7 percentage points in estimating the sea ice concentration.
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| 6. |
- Carvajal, Gisela, 1983, et al.
(author)
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Operational Retrieval of Sea-Surface Dynamics from SAR data for Safety and Security
- 2010
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Conference paper (other academic/artistic)abstract
- The European Community’s Seventh Framework Programmeproject SECTRONIC will provide informationon safety and security to maritime infrastructures at aglobal scale. Focus of this paper is on two implementedalgorithms that employ data from Synthetic ApertureRadar (SAR) sensors. The first algorithm retrieves winddirection directly from the SAR image using standard imageprocessing techniques. Wind speed is estimated bythe inversion of a geophysical model function (GMF),having wind direction estimates as an input. Operationalimplemetation of mentioned algorithms is described andan example of results is provided.
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| 7. |
- Eriksson, Leif, 1970, et al.
(author)
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ALOS PALSAR calibration and validation activities in Sweden
- 2008
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In: Proceedings of The First Joint PI Symposium of ALOS Data Nodes for ALOS Science Program in Kyoto, Kyoto, Japan, 19 - 23 November, 2007. - 1349-113X. - 9784906653041 ; JAXA-SP-07-012
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Conference paper (other academic/artistic)
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| 8. |
- Eriksson, Leif, 1970, et al.
(author)
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ALOS PALSAR Calibration and Validation Results from Sweden
- 2007
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In: IEEE Geoscience and Remote Sensing Symposium (IGARSS 2007), Barcelona, Spain, July 23-27, 2007. ; DOI: 10.1109/IGARSS.2007.4423115, s. 1589-1592
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Conference paper (other academic/artistic)abstract
- In 2006 calibration activities for ALOS PALSAR wereconducted in Sweden. Four five-metre trihedral corner reflectorsand three smaller dihedral reflectors were deployed and operatedduring eight months. 23 PALSAR scenes were acquired over thecalibration site allowing an evaluation of the quality and temporalstability of the data. Results show that the co-polarized datahave been stable during the whole calibration period with variationsin the trihedral responses lower than 0.7 dB. The measuredresolution in azimuth was 4.4 m and in slant range 4.7 m forsingle polarization images and 9.5 m for polarimetric data. Forthe cross-polarized data large variations in the dihedral responseswere found. It is assumed that this is caused by a larger sensitivityto pointing errors. For the polarimetric data, estimation ofFaraday rotation gave values ranging from 0.1º to 3º.
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| 9. |
- Eriksson, Leif, 1970, et al.
(author)
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Backscatter signatures of wind-thrown forest in satellite SAR images
- 2012
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In: International Geoscience and Remote Sensing Symposium (IGARSS). - 2153-6996 .- 2153-7003. - 9781467311588 ; , s. 6435-6438
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Conference paper (peer-reviewed)abstract
- Two field experiments have been conducted in Sweden to allow an evaluation of the backscatter signatures of wind-thrown forest from L-band, C-band and X-band Synthetic Aperture Radar. When the trees are felled the backscattered signal from TerraSAR-X (X-band) increase with about 1.5 dB, while for ALOS PALSAR (L-band) a decrease with the same amount is observed. Radar images with fine spatial resolution also show shadowing effects that should be possible to use for identification of storm felled forest.
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| 10. |
- Eriksson, Leif, 1970, et al.
(author)
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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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In: Proceedings of the ESA Living Planet Symposium 2010, 28 June - 2 July 2010, Bergen, Norway. ; ESA SP-686
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Conference paper (other academic/artistic)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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