• 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 ...
    • Machine Learning Automatic Model Selection Algorithm for Oceanic Chlorophyll-a Content Retrieval 

      Blix, Katalin; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-17)
      Ocean Color remote sensing has a great importance in monitoring of aquatic environments. The number of optical imaging sensors onboard satellites has been increasing in the past decades, allowing to retrieve information about various water quality parameters of the world’s oceans and inland waters. This is done by using various regression algorithms to retrieve water quality parameters from remotely ...
    • Machine Learning for Arctic Sea Ice Physical Properties Estimation Using Dual-Polarimetric SAR Data 

      Blix, Katalin; Espeseth, Martine; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-22)
      This work introduces a novel method that combines machine learning (ML) techniques with dual-polarimetric (dual-pol) synthetic aperture radar (SAR) observations for estimating quad-polarimetric (quad-pol) parameters, which are presumed to contain geophysical sea ice information. In the training phase, the output parameters are generated from quad-pol observations obtained by Radarsat-2 (RS2), and ...
    • Machine Learning simulations of quad-polarimetric features from dual-polarimetric measurements over sea ice 

      Blix, Katalin; Espeseth, Martine; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06)
      In this paper, we investigated the capabilities of the Gaussian Process Regression (GPR) algorithm in predicting of two quad-polarimetric parameters (relevant for sea ice analysis) from 6-dimensional dual-polarimetric input vectors. The GRP is trained on few hundred samples selected randomly from an image subset, and tested on the entire image. The performance is assessed by visual comparisons, and ...
    • 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, ...
    • Monitoring glacier changes using multitemporal multipolarization SAR images 

      Akbari, Vahid; Doulgeris, Anthony Paul; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • A Multimodal Feature Selection Method for Remote Sensing Data Analysis Based on Double Graph Laplacian Diagonalization 

      Khachatrian, Eduard; Chlaily, Saloua; Eltoft, Torbjørn; Marinoni, Andrea (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-13)
      When dealing with multivariate remotely sensed records collected by multiple sensors, an accurate selection of information at the data, feature, or decision level is instrumental in improving the scenes’ characterization. This will also enhance the system’s efficiency and provide more details on modeling the physical phenomena occurring on the Earth’s surface. In this article, we introduce a flexible ...
    • 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, ...
    • A new spectral harmonization algorithm for Landsat-8 and Sentinel-2 remote sensing reflectance products using machine learning: a case study for the Barents Sea (European Arctic) 

      Asim, Muhammad; Matsuoka, Atsushi; Ellingsen, Pål Gunnar; Brekke, Camilla; Eltoft, Torbjørn; Blix, Katalin (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-12)
      The synergistic use of Landsat-8 operational land imager (OLI) and Sentinel-2 multispectral instrument (MSI) data products provides an excellent opportunity to monitor the dynamics of aquatic ecosystems. However, the merging of data products from multisensors is often adversely affected by the difference in their spectral characteristics. In addition, the errors in the atmospheric correction (AC) ...
    • 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)
    • 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)
    • Performance Analysis of Roll-Invariant PolSAR Parameters from C-band images with Regard to Sea Ice Type Separation 

      Ratha, Debanshu; Johansson, Malin; Marinoni, Andrea; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06)
      The Polarimetric Synthetic Aperture Radar (PolSAR) backscatter from a target is dependent on the incidence angle. Consequently, the associated roll invariant parameters are affected by changes in incidence angle. In this work, we identify a few of these parameters that remain robust in identifying sea ice features even under large incidence angle variations. We conclude that the helicity angle ...
    • Polarimetric SAR Change Detection with the Complex Hotelling-Lawley Trace Statistic 

      Akbari, Vahid; Anfinsen, Stian Normann; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Moser, Gabriele; Serpico, Sebastian Bruno (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-15)
      In this paper, we propose a new test statistic for unsupervised change detection in polarimetric radar images. We work with multilook complex covariance matrix data, whose underlying model is assumed to be the scaled complex Wishart distribution. We use the complex-kind Hotelling-Lawley trace statistic for measuring the similarity of two covariance matrices. The distribution of the Hotelling-Lawley ...
    • Remote Sensing of Water Quality Parameters over Lake Balaton by Using Sentinel-3 OLCI 

      Blix, Katalin; Pálffy, Károly; Tóth, Viktor R.; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-11)
      The Ocean and Land Color Instrument (OLCI) onboard Sentinel 3A satellite was launched in February 2016. Level 2 (L2) products have been available for the public since July 2017. OLCI provides the possibility to monitor aquatic environments on 300 m spatial resolution on 9 spectral bands, which allows to retrieve detailed information about the water quality of various type of waters. It has only been ...
    • Retrieval of Marine Surface Slick Dielectic Properties From Radarsat-2 Data via a Polarimetric Two-Scale Model 

      Quigley, Cornelius; Brekke, Camilla; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-27)
      We propose the use of a polarimetric two-scale surface scattering model to retrieve the dielectric parameters of oil slick from the polarimetric synthetic aperture radar. The ocean surface is modeled as an ensemble of randomly orientated, slightly roughened, tilted facets, for which the small perturbation model is assumed to be valid under the condition of no tilt. The orientation of the random ...
    • SAR and Passive Microwave Fusion Scheme: A Test Case on Sentinel-1/AMSR-2 for Sea Ice Classification 

      Khachatrian, Eduard; Dierking, Wolfgang; Chlaily, Saloua; Eltoft, Torbjørn; Dinessen, Frode; Hughes, Nick; Marinoni, Andrea (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-14)
      The most common source of information about sea ice conditions is remote sensing data, especially images obtained from synthetic aperture radar (SAR) and passive microwave radiometers (PMR). Here we introduce an adaptive fusion scheme based on Graph Laplacians that allows us to retrieve the most relevant information from satellite images. In a first test case, we explore the potential of sea ice ...
    • Sea Ice Classification of SAR Imagery Based on Convolution Neural Networks 

      Khaleghian, Salman; Ullah, Habib; Kræmer, Thomas; Hughes, Nick; Eltoft, Torbjørn; Marinoni, Andrea (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-29)
      We explore new and existing convolutional neural network (CNN) architectures for sea ice classification using Sentinel-1 (S1) synthetic aperture radar (SAR) data by investigating two key challenges: binary sea ice versus open-water classification, and a multi-class sea ice type classification. The analysis of sea ice in SAR images is challenging because of the thermal noise effects and ambiguities ...
    • 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 ...