• Incorporating Incidence Angle Variation into Sar Image Segmentation 

      Doulgeris, Anthony Paul; Cristea, Anca (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-05)
      We present a new approach for incorporating incidence angle derived synthetic aperture radar (SAR) brightness variation directly into SAR image analysis. This approach is unique in that the incidence angle dependency is modeled explicitly into the probability density function rather than an image-wide pre-processing `correction'. It can then be used for supervised and unsupervised image analysis, ...
    • Incorporating Incidence Angle Variation into Sar Image Segmentation 

      Doulgeris, Anthony Paul; Cristea, Anca (Journal article; Tidsskriftartikkel; Peer reviewed, 2018)
      We present a new approach for incorporating incidence angle derived synthetic aperture radar (SAR) brightness variation directly into SAR image analysis. This approach is unique in that the incidence angle dependency is modeled explicitly into the probability density function rather than an image-wide pre-processing ‘correction’. It can then be used for supervised and unsupervised image analysis, ...
    • Integrating Incidence Angle Dependencies Into the Clustering-Based Segmentation of SAR Images 

      Cristea, Anca; Van Houtte, Jeroen; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-28)
      Synthetic aperture radar systems perform signal acquisition under varying incidence angles and register an implicit intensity decay from near to far range. Owing to the geometrical interaction between microwaves and the imaged targets, the rates at which intensities decay depend on the nature of the targets, thus rendering single-rate image correction approaches only partially successful. The decay, ...
    • Integrating incidence-angle compensation in the segmentation of UAVSAR images 

      Cristea, Anca; Doulgeris, Anthony Paul (Conference object; Konferansebidrag, 2018)
      <p>SAR images display a characteristic intensity variation along the range dimension, caused by the fact that the backscattered intensities depend on the incidence angle. In the case of wide-swath images, this intensity variation from near range to far range is significant enough to affect image segmentation performed on absolute intensity values. The effects are an over-segmentation which creates ...
    • A K-Wishart Markov random field model for clustering of polarimetric SAR imagery 

      Akbari, Vahid; Moser, Gabriele; Doulgeris, Anthony Paul; Anfinsen, Stian Normann; Eltoft, Torbjørn; Serpico, Sebastian Bruno (Peer reviewed; Bokkapittel; Bok; Book; Chapter, 2011-10-20)
      A clustering method that combines an advanced statistical distribution with spatial contextual information is proposed for multilook polarimetric synthetic aperture radar (PolSAR) data. It is based on a Markov random field (MRF) model that integrates a K-Wishart distribution for the PolSAR data statistics conditioned to each image cluster and a Potts model for the spatial context. Specifically, the ...
    • A K-Wishart Markov random field model for clustering of polarimetric SAR imagery 

      Moser, Gabriele; Akbari, Vahid; Eltoft, Torbjørn; Doulgeris, Anthony Paul; Anfinsen, Stian Normann; Sebastian, Serpico (Conference object; Konferansebidrag, 2011)
    • Late summer sea ice segmentation with multi-polarisation SAR features in C- and X-band 

      Fors, Ane Schwenke; Brekke, Camilla; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Renner, Angelika; Gerland, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-01)
      In this study we investigate the potential of sea ice segmentation by C- and X-band multi-polarisation synthetic aperture radar (SAR) features during late summer. Five high-resolution satellite SAR scenes were recorded in the Fram Strait covering iceberg- fast first-year and old sea ice during a week with air temperatures varying around zero degrees Celsius. In situ data consisting of sea ice ...
    • Leads in Arctic pack ice enable early phytoplankton blooms below snow-covered sea ic 

      Assmy, Philipp; Fernández-Méndez, Mar; Duarte, Pedro; Meyer, Amelie; Randelhoff, Achim; Mundy, Christopher John; Olsen, Lasse; Kauko, Hanna M.; Bailey, Allison; Chierici, Melissa; Cohen, Lana; Doulgeris, Anthony Paul; Ehn, Jens K.; Fransson, Agneta; Gerland, Sebastian; Hop, Haakon; Hudson, Stephen R.; Hughes, Nick; Itkin, Polona; Johnsen, Geir; King, Jennifer A.; Koch, Boris P.; Koenig, Zoe; Kwasniewski, Slawomir; Laney, Samuel R.; Nikolaus, Marcel; Pavlov, Alexey K.; Polashenski, Christopher M.; Provost, Christine; Rösel, Anja; Sandbu, Marthe; Spreen, Gunnar; Smedsrud, Lars H.; Sundfjord, Arild; Taskjelle, Torbjørn; Tatarek, Agnieszka; Wiktor, Josef; Wagner, Penelope Mae; Wold, Anette; Steen, Harald; Granskog, Mats A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-19)
      The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One critical challenge is to understand how productivity will change within the next decades. Recent studies have reported extensive phytoplankton blooms beneath ponded sea ice during summer, indicating ...
    • Mapping sea-ice types from Sentinel-1 considering the surface-type dependent effect of incidence angle 

      Lohse, Johannes; Doulgeris, Anthony Paul; Dierking, Wolfgang (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-23)
      Automated classification of sea-ice types in Synthetic Aperture Radar (SAR) imagery is complicated by the class-dependent decrease of backscatter intensity with Incidence Angle (IA). In the log-domain, this decrease is approximately linear over the typical range of space-borne SAR instruments. A global correction does not consider that different surface types show different rates of decrease in ...
    • Model-Based Polarimetric Decomposition With Higher Order Statistics 

      Eltoft, Torbjørn; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-11)
      This letter presents a new general framework for solving polarimetric target decompositions that extends them to use more statistical information and include radar texture models. Polarimetric target decomposition methods generally have more physical parameters than equations and are, thus, underdetermined and have no unique solution. The common approach to solve them is to make certain assumptions, ...
    • Modeling Microwave Scattering From Rough Sea Ice Surfaces 

      Xu, Xu; Doulgeris, Anthony Paul; Melandsø, Frank; Brekke, Camilla (Conference object; Konferansebidrag, 2017)
      In this paper, COMSOL Multiphysics® was used to simulate the microwave scattering from the rough sea ice surface. A nonperiodic model and a periodic model were built. The nonperiodic model considers the rough surface of finite length and introduces a tapered incident wave. In this model, the strategy of total and scattered-field decomposition (TSFD) was used to formulate the finite-element method ...
    • Monitoring glacier changes using multitemporal multipolarization SAR images 

      Akbari, Vahid; Doulgeris, Anthony Paul; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • A Multitexture Model for Multilook Polarimetric Synthetic Aperture Radar Data 

      Eltoft, Torbjørn; Anfinsen, Stian Normann; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      A statistical model for multilook polarimetric radar data is presented where the polarimetric channels are associated with individual texture variables having potentially different statistical properties. The feasibility of producing closed form probability density functions under certain restrictions is outlined. Mellin kind statistics are derived under various assumptions on the texture variables, ...
    • Non-gaussian clustering of SAR images for glacier change detection 

      Akbari, Vahid; Doulgeris, Anthony Paul; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel, 2010-12)
      Our aim is to use unsupervised, non-Gaussian clustering of Arctic glaciers for post-classification change detection. Firstly, we demonstrate the consistency of non-Gaussian clustering algorithms for Envisat ASAR images by characterizing the expected random error level for different SAR acquisition conditions (such as incidence angle). This allows us to determine whether an observed variation is ...
    • Non-Gaussian Clustering of SAR images for Glacier Change Detection 

      Akbari, Vahid; Eltoft, Torbjørn; Doulgeris, Anthony Paul (Conference object; Konferansebidrag, 2010)
    • Non-Gaussian statistical analysis of polarimetric synthetic aperture radar images 

      Doulgeris, Anthony Paul (Doctoral thesis; Doktorgradsavhandling, 2011-02-18)
      This thesis describes general methods to analyse polarimetric synthetic aperture radar images, with the primary application of unsupervised image segmentation. The fundamental physics of electromagnetic scattering from distributed targets leads to the image phenomenon called speckle. Speckle is shown to be potentially non-Gaussian and several statistical distributions are investigated. Non-Gaussianity ...
    • Numerical Analysis of Microwave Scattering from Layered Sea Ice Based on the Finite Element Method 

      Xu, Xu; Brekke, Camilla; Doulgeris, Anthony Paul; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-21)
      A two-dimensional scattering model based on the Finite Element Method (FEM) is built for simulating the microwave scattering of sea ice, which is a layered medium. The scattering problem solved by the FEM is formulated following a total- and scattered-field decomposition strategy. The model set-up is first validated with good agreements by comparing the results of the FEM with those of the small ...
    • Numerical Simulation of Microwave Scattering from Sea Ice Based on The Finite Element Method 

      Xu, Xu; Doulgeris, Anthony Paul; Melandsø, Frank; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-03)
      In this paper, a 2-dimensional scattering model for sea ice based on the Finite Element Method (FEM) is presented. The scattering problem is formulated following a physics-separate strategy. The wave in the air domain is expressed by the scattered field formulation, while the wave in the sea ice domain is expressed by the total field formulation. The two separate physics and formulations are coupled ...
    • On Importance of Off-Diagonal Elements in the Polarimetric Covariance Matrix: A Sea Ice Application Perspective 

      Ratha, Debanshu; Doulgeris, Anthony Paul; Marinoni, Andrea; Eltoft, Torbjørn (Conference object; Konferansebidrag, 2023-06)
    • On the potential of hand-held GPS tracking of fjord ice features for remote-sensing validation 

      Negrel, Jean; Gerland, Sebastian; Doulgeris, Anthony Paul; Lauknes, Tom Rune; Rouyet, Line (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-14)
      Research on young thin sea ice is essential to understand the changes in the Arctic. But it is also the most challenging to investigate, both in situ and from satellites. If satellite remote sensing techniques are developing rapidly, fieldwork remains crucial for the mandatory validation of such data. In April 2016, an Arctic fieldwork campaign was conducted at Kongsfjorden, Svalbard. This campaign ...