| 1. |
- Carvajal, Gisela, 1983, et al.
(author)
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Comparison between current fields detected with infrared radiometry and modeled currents around Sweden
- 2013
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In: 33rd IEEE International Geoscience and Remote Sensing Symposium (IGARSS); 2013, Melbourne. - 9781479911141 ; , s. 1270-1273
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Conference paper (peer-reviewed)abstract
- The understanding of the relationship between surface currents derived from weather models and remote sensing data is essential in order to produce an improved and integrated surface current information of high quality and resolution. The large availability of satellite derived infrared radiometer data at the high latitudes of the coastal waters surrounding Sweden makes the Maximum Cross Correlation (MCC) method a feasible alternative to produce real time measurements of surface currents. This work compares current retrievals from the MCC method and model data around Sweden. Our results indicate a similar magnitude for both sources of current fields in most of the locations. However, there exist small discrepancies in the localization of the larger current values. Also, the MCC retrievals generally present more features than the modeled ones. Possible reasons for these discrepancies might be the MCC detection of circulation patterns not predicted by the model, or the depreciation in the MCC performance due to the influence of diurnal variability of the sea surface temperature, wind driven mixing due to upwelling or tides.
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| 2. |
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| 3. |
- Johansson, Malin, 1980, et al.
(author)
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Remote sensing for risk analysis of oil spills in the Arctic Ocean
- 2013
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In: Proceedings of the ESA Living Planet Symposium 2013, 9 - 13 September 2013, Edinburgh, UK.
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Conference paper (other academic/artistic)abstract
- Predicted decreases in sea-ice extent and shift from multiyear ice to seasonal ice open up for commercial shipping routes within the Arctic. With expected further growth of maritime activities the potential threat of accidents is increasing. Moreover, there is a lack of information on how an oil spill would affect the Arctic Ocean environment. A robust tool following international risk assessment standards is therefore vital to 1) try to prevent oil spills through use of scenario runs and 2) increase the possibilities to delimit the damage should a spill occur. We use remote sensing images to extract information about oil spill redistribution mechanisms. This combined with information about estimated volume, type ofoil and ecotoxicological data enables identification of areas in the Arctic Ocean especially vulnerable to maritimeactivities. We also include estimates on the probability ofan oil spill occurrence.
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| 5. |
- Berg, Anders, 1983, et al.
(author)
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Comparison between SAR derived sea ice displacement and hindcasts by the operational ocean model HIROMB
- 2013
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In: Proceedings of the IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Melbourne, Australia, July 21-26, 2013. - 9781479911141 ; , s. 3630-3633
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Conference paper (peer-reviewed)abstract
- The purpose of this paper is to compare measurements of sea ice displacement from SAR imagery with ice floe drift trajectories modeled by the operational ocean circulation model HIROMB. The study examines the ice movement in the Fram Strait during a two-week period in April, 2011. The results indicate that the HIROMB model overestimates the drift speed by a factor 1 - 2.5, which may be attributed to an underestimated thickness of the ice. The model data also exhibit a directional offset in the positive clockwise direction of 10 - 30 degrees over the whole study region. The results of this study may be used to direct the model development and improve the model initialization.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Berg, Anders, 1983, et al.
(author)
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Investigation of a Hybrid Algorithm for Sea Ice Drift Measurements Using Synthetic Aperture Radar Images
- 2014
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In: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892 .- 1558-0644. ; 52:8, s. 5023 - 5033
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Journal article (peer-reviewed)abstract
- Areal matching by phase correlation and feature tracking are two complementary methods used to measure sea ice drift between synthetic aperture radar images. This paper evaluates a new algorithm that combines the two methods. Areal matching is improved by new methods to handle large motions and rotated ice. It is shown that areal rotation can be resolved using a frequency-domain approach. Image segmentation is a prerequisite for feature tracking and achieved by a new method that performs better than Otsu's method for two-component Gaussian mixture distributions. A circular weighted median filter is found to be suitable for the filtering of the motion field. The algorithm is evaluated through a thorough analysis of the response and sensitivity to various algorithm settings. The accuracy of the algorithm varies by up to 50% for one image pair within the studied range of parameter settings, thus indicating the need for a proper initialization of the algorithm.
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| 10. |
- Berg, Anders, 1983, et al.
(author)
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Observations and Analysis of Sea Ice Motion with the Ice Buoy DRIVA during the 2010 Spring Field Campaign in the Bay of Bothnia
- 2011
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Reports (other academic/artistic)abstract
- The ice drift buoy DRIVA is tested for the first time in the environment for which it was designed. The communication with the buoy via satellite phone is working well. Temperatures could be read during the entire test period, and except from an unexplained loss of GPS data during 20 days, the GPS position was transmitted as expected. The rotary encoders did not function properly during the campaign. A sea ice drift algorithm is validated against the buoy data using ten image pairs acquired by the C‐band SAR satellite ENVISAT. The accuracy of the algorithm decreases with time and highest accuracy is achieved with the first three image pairs. For the first image pair, the computed translation differs by only 160 m from the translation measured by the buoy, which is a good result considering the pixel resolution of approximately 150 m. The root mean square error of the algorithm for the first three image pairs is 5% for the ice speed and 4 degrees for the direction of the ice. The decreasing accuracy can be related to an increase of melting during the campaign. The sea ice is very dynamic during the period, making the images very different. Large ice floes break into smaller pieces after a short time. As the ice floes melt and get smaller, rotation increases, and the shapes of the ice floes are not preserved. It appears that the buoy floats within a streak of slush ice during the last days of the time period. Tracking of the ice is more difficult under such circumstances, because the contours of an area of slush ice are constantly changing.
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