• Alignment of Multifrequency SAR Images Acquired over Sea Ice Using Drift Compensation 

      Demchev, Denis; Eriksson, Leif E.B.; Hildeman, Anders; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-07)
      In this article, 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 multifrequency SAR images acquired at different times. Images obtained at different radar frequencies provide ...
    • Automatic Detection of Small Icebergs in Fast Ice Using Satellite Wide-Swath SAR Images 

      Soldal, Ingri Halland; Dierking, Wolfgang Fritz Otto; Korosov, Anton; Marino, Armando (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-03)
      Automatic detection of icebergs in satellite images is regarded a useful tool to provide information necessary for safety in Arctic shipping or operations over large ocean areas in near-real time. In this work, we investigated the feasibility of automatic iceberg detection in Sentinel-1 Extra Wide Swath (EWS) SAR images which follow the preferred image mode in operational ice charting. As test region, ...
    • Automatic Selection of Relevant Attributes for Multi-Sensor Remote Sensing Analysis: A Case Study on Sea Ice Classification 

      Khachatrian, Eduard; Chlaily, Saloua; Eltoft, Torbjørn; Dierking, Wolfgang Fritz Otto; Dinessen, Frode; Marinoni, Andrea (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-26)
      It is of considerable benefit to combine information obtained from different satellite sensors to achieve advanced and improved characterization of sea ice conditions. However, it is also true that not all the information is relevant. It may be redundant, corrupted, or unnecessary for the given task, hence decreasing the performance of the algorithms. Therefore, it is crucial to select an optimal ...
    • A comparison of constant false alarm rate object detection algorithms for iceberg identification in L- and C-band SAR imagery of the Labrador Sea 

      Færch, Laust; Dierking, Wolfgang Fritz Otto; Hughes, Nick; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-15)
      In this study, we pursue two objectives: first, we compare six different “constant false alarm rate” (CFAR) algorithms for iceberg detection in SAR images, and second, we investigate the effect of radar frequency by comparing the detection performance at C- and L-band. The SAR images were acquired over the Labrador Sea under melting conditions. In an overlapping optical Sentinel-2 image, 492 icebergs ...
    • Dynamics of the Terra Nova Bay Polynya: The potential of multi-sensor satellite observations 

      Hollands, Thomas; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-10)
      Research on processes leading to formation, maintenance, and disappearance of polynyas in the Polar Regions benefits significantly from the use of different types of remote sensing data. The Sentinels of the European Space Agency (ESA), together with other satellite missions, provide a variety of data from different parts of the electromagnetic spectrum, at different spatial scales, and with ...
    • Estimating statistical errors in retrievals of ice velocity and deformation parameters from satellite images and buoy arrays 

      Dierking, Wolfgang Fritz Otto; Stern, Harry L.; Hutchings, Jennifer K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-15)
      The objective of this note is to provide the background and basic tools to estimate the statistical error of deformation parameters that are calculated from displacement fields retrieved from synthetic aperture radar (SAR) imagery or from location changes of position sensors in an array. We focus here specifically on sea ice drift and deformation. In the most general case, the uncertainties of ...
    • Impact of sea ice drift retrieval errors, discretization and grid type on calculations of ice deformation 

      Griebel, Jakob; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-03)
      We studied two issues to be considered in the calculation of parameters characterizing sea ice deformation: the effect of uncertainties in an automatically retrieved sea ice drift field, and the influence of the type of drift vector grid. Sea ice deformation changes the local ice mass balance and the interaction between atmosphere, ice, and ocean, and constitutes a hazard to marine traffic and ...
    • Improving satellite-based monitoring of the polar regions: Identification of research and capacity gaps 

      Gabarró, Carolina; Hughes, Nick; Wilkinson, Jeremy; Bertino, Laurent; Bracher, Astrid; Diehl, Thomas; Dierking, Wolfgang Fritz Otto; Gonzalez-Gambau, Veronica; Lavergne, Thomas; Madurell, Theresa; Malnes, Eirik; Wagner, Penelope Mae (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-17)
      We present a comprehensive review of the current status of remotely sensed and in situ sea ice, ocean, and land parameters acquired over the Arctic and Antarctic and identify current data gaps through comparison with the portfolio of products provided by Copernicus services. While we include several land parameters, the focus of our review is on the marine sector. The analysis is facilitated by the ...
    • Incident Angle Dependence of Sentinel-1 Texture Features for Sea Ice Classification 

      Lohse, Johannes; Doulgeris, Anthony Paul; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)
      Robust and reliable classification of sea ice types in synthetic aperture radar (SAR) images is needed for various operational and environmental applications. Previous studies have investigated the class-dependent decrease in SAR backscatter intensity with incident angle (IA); others have shown the potential of textural information to improve automated image classification. In this work, we investigate ...
    • Linking sea ice deformation to ice thickness redistribution using high-resolution satellite and airborne observations 

      Von Albedyll, Luisa; Haas, Christian; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-04)
      An unusual, large, latent-heat polynya opened and then closed by freezing and convergence north of Greenland’s coast in late winter 2018. The closing presented a natural but well-constrained full-scale ice deformation experiment. We observed the closing of and deformation within the polynya with satellite synthetic-aperture radar (SAR) imagery and measured the accumulated effects of dynamic ...
    • Method for detection of leads from Sentinel-1 SAR images 

      Murashkin, Dmitrii; Spreen, Gunnar; Huntemann, Marcus; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-05)
      The presence of leads with open water or thin ice is an important feature of the Arctic sea ice cover. Leads regulate the heat, gas and moisture fluxes between the ocean and atmosphere and are areas of high ice growth rates during periods of freezing conditions. Here, an algorithm providing an automatic lead detection based on synthetic aperture radar images is described that can be applied to a ...
    • A method to improve high-resolution sea ice drift retrievals in the presence of deformation zones 

      Griebel, Jakob; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-12)
      Retrievals of sea ice drift from synthetic aperture radar (SAR) images at high spatial resolution are valuable for understanding kinematic behavior and deformation processes of the ice at different spatial scales. Ice deformation causes temporal changes in patterns observed in sequences of SAR images; which makes it difficult to retrieve ice displacement with algorithms based on correlation and ...
    • A New Retracking Algorithm for Retrieving Sea Ice Freeboard from CryoSat-2 Radar Altimeter Data during Winter–Spring Transition 

      Shen, Xiaoyi; Similä, Markku H.; Dierking, Wolfgang Fritz Otto; Zhang, Xi; Ke, Changqing; Liu, Meijie; Wang, Manman (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-20)
      A new method called Bézier curve fitting (BCF) for approximating CryoSat-2 (CS-2) SAR-mode waveform is developed to optimize the retrieval of surface elevation of both sea ice and leads for the period of late winter/early spring. We found that the best results are achieved when the retracking points are fixed on positions at which the rise of the fitted Bézier curve reaches 70% of its peak in case ...
    • Object-based detection of linear kinematic features in sea ice 

      Linow, Stefanie; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-18)
      Inhomogenities in the sea ice motion field cause deformation zones, such as leads, cracks and pressure ridges. Due to their long and often narrow shape, those structures are referred to as Linear Kinematic Features (LKFs). In this paper we specifically address the identification and characterization of variations and discontinuities in the spatial distribution of the total deformation, which ...
    • An Optimal Decision-Tree Design Strategy and Its Application to Sea Ice Classification from SAR Imagery 

      Lohse, Johannes; Doulgeris, Anthony Paul; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-03)
      We introduce the fully automatic design of a numerically optimized decision-tree algorithm and demonstrate its application to sea ice classification from SAR data. In the decision tree, an initial multi-class classification problem is split up into a sequence of binary problems. Each branch of the tree separates one single class from all other remaining classes, using a class-specific selected feature ...
    • Results of the Dragon 4 Project on New Ocean Remote Sensing Data for Operational Applications 

      Gibert, Ferran; Boutin, Jacqueline; Dierking, Wolfgang Fritz Otto; Granados, Alba; Li, Yan; Makhoul, Eduard; Meng, Junmin; Supply, Alexandre; Vendrell, Ester; Vergely, Jean-Luc; Wang, Jin; Yang, Jungang; Xiang, Kunsheng; Yin, Xiaobin; Zhang, Xi (Journal article; Tidsskriftsartikkel, 2021-07-20)
      This paper provides an overview of the Dragon 4 project dealing with operational monitoring of sea ice and sea surface salinity (SSS) and new product developments for altimetry data. To improve sea ice thickness retrieval, a new method was developed to match the Cryosat-2 radar waveform. Additionally, an automated sea ice drift detection scheme was developed and tested on Sentinel-1 data, and the ...
    • Sea ice local surface topography from single-pass satellite InSAR measurements: A feasibility study 

      Dierking, Wolfgang Fritz Otto; Lang, Oliver; Busche, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-29)
      Quantitative parameters characterizing the sea ice surface topography are needed in geophysical investigations such as studies on atmosphere–ice interactions or sea ice mechanics. Recently, the use of space-borne single-pass interferometric synthetic aperture radar (InSAR) for retrieving the ice surface topography has attracted notice among geophysicists. In this paper the potential of InSAR ...
    • Sea Ice Remote Sensing—Recent Developments in Methods and Climate Data Sets 

      Sandven, Stein; Spreen, Gunnar; Heygster, Georg; Girard-Ardhuin, Fanny; Farrell, Sinéad L.; Dierking, Wolfgang Fritz Otto; Allard, Richard A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-03)
      Sea ice monitoring by polar orbiting satellites has been developed over more than four decades and is today one of the most well-established applications of space observations. This article gives an overview of data product development from the first sensors to the state-of-the-art regarding retrieval methods, new products and operational data sets serving climate monitoring as well as daily operational ...
    • Sea ice segmentation using Tandem-X pursuit mono static and alternative bistatic modes 

      Yitayew, Temesgen Gebrie; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Dierking, Wolfgang Fritz Otto; Brekke, Camilla; Rösel, Anja (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)
      In this paper we investigate interferometric pairs of SAR images acquired by Tandem-X with the monostatic pursuit and the alternative bistatic modes for sea ice segmentation. The individual SAR images are modelled as non-Gaussian, and from the modelled data different features are extracted, stacked together and clustered. The interferometric coherence is regarded as an additional feature and utilized ...