English
norskBlar i forfatter "Doulgeris, Anthony Paul"
Viser treff 1-20 av 58
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An Advanced Non-Gaussian Feature Space Method for POL-SAR Image Segmentation
(Conference object; Konferansebidrag, 2013)This work extends upon our simple feature-based multichannel SAR segmentation method to incorporate highly desirable statistical properties into a computationally simple approach. The desirable properties include Markov random field contextual smoothing and goodness-of-fit testing to automatically obtain the significant number of classes. To achieve this we need to find an explicit class model to ... -
Analysis of evolving oil spills in full-polarimetric and hybrid-polarity SAR
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-25)Oil spill detection using a time series of images acquired off Norway in June 2015 with the uninhabited aerial vehicle synthetic aperture radar is examined. The relative performance of a set of features derived from quad-polarization versus hybrid-polarity (HP) modes in detection of various types of slicks as they evolve on a high wind driven sea surface is evaluated. It is shown that the HP mode ... -
Arctic Field Summer Schools: training and awareness in the Arctic
(Conference object; Konferansebidrag, 2020-01)A series of three summer schools engaged nearly fifty graduate students in exploring science questions related to current Arctic challenges, and brought together leading Arctic researchers from the partner institutions. Each partner organised a Field School and each had their own unique styles and emphasis. This collaboration aimed to deepen the Arctic knowledge of the young generation, and to create ... -
Arctic Field Summer Schools: training the next generation of Arctic researchers
(Conference object; Konferansebidrag, 2018)<p>The Arctic Field Summer Schools project is funded by the Research Council of Norway (NFR) and Norwegian Centre for International Cooperation in Education (SIU), under the grant agreement number 261786/H30. <p>The project supports research and education collaboration among UiT - The Arctic University of Norway, University of Alaska Fairbanks (UAF), USA and University of Calgary (UC), Canada. <p>Through ... -
Aspects of model-based decompositions in radar polarimetry
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-12)In this paper, we further analyse the problem that polarimetric target decomposition methods in general have more physical parameters than equations, making the decomposition under-determined and hence have no unique solution. The common approach to get around this problem is to make certain assumptions, thus fixing one or more parameters, allowing the other free parameters to be solved from the set ... -
Assessing polarimetric SAR sea-ice classifications using consecutive day images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015)This paper investigates automatic segmentation and classification of C-band, polarimetric synthetic aperture radar (SAR) satellite images of Arctic sea ice under freezing conditions prior to melt. The objective is to investigate the robustness of the results obtained under slightly varying environmental conditions and different viewing geometries. Initially, three geographically overlapping SAR ... -
Automatic Detection of Low-Backscatter Targets in the Arctic Using Wide Swath Sentinel-1 Imagery
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-12)Low backscatter signatures in synthetic aperture radar (SAR) imagery are characteristic to surfaces that are highly smooth and specular reflective of microwave radiation. In the Arctic, these typically represent newly formed sea ice, oil spills, and localized weather phenomena such as low wind or rain cells. The operational monitoring of low backscatter targets can benefit from a stronger integration ... -
An Automatic U-distribution and Markov Random Field Segmentation Algorithm for PolSAR Images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015) -
A change detector for polarimetric SAR data based on the relaxed Wishart distribution
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-12)In this paper, we present an unsupervised change detection method for polarimetric synthetic aperture radar (PolSAR) images based on the relaxed Wishart distribution. Most polarimetric change detectors assume the Gaussian-based complex Wishart model for multilook covariance matrices, which is only satisfied for homogeneous areas with fully developed speckle and no texture. Liu et al. recently proposed ... -
A comparison of constant false alarm rate object detection algorithms for iceberg identification in L- and C-band SAR imagery of the Labrador Sea
(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 ... -
Comparison of feature based segmentation of full polarimetric SAR satellite sea ice images with manually drawn ice charts
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)In this paper we investigate the performance of an algorithm for automatic segmentation of full polarimetric, synthetic aperture radar (SAR) sea ice scenes. The algorithm uses statistical and polarimetric properties of the backscattered radar signals to segment the SAR image into a specified number of classes. This number was determined in advance from visual inspection of the SAR image and by ... -
Consistent ice and open water classification combining historical synthetic aperture radar satellite images from ERS-1/2, Envisat ASAR, RADARSAT-2 and Sentinel-1A/B
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-17)Synthetic Aperture Radar (SAR) satellite images are used to monitor Arctic sea ice, with systematic data records dating back to 1991. We propose a semi-supervised classification method that separates open water from sea ice and can utilise ERS-1/2, Envisat ASAR, RADARSAT-2 and Sentinel-1 SAR images. The classification combines automatic segmentation with a manual segment selection stage. The ... -
Consistent ice and open water classification combining historical synthetic aperture radar satellite images from ERS-1/2, Envisat ASAR, RADARSAT-2, and Sentinel-1A/B
(Journal article; Tidsskriftartikkel, 2020) -
Correction and Characterization of Radio Frequency Interference Signatures in L-band Synthetic Aperture Radar Data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Radio frequency interference (RFI) is a known issue in low-frequency radar remote sensing. In synthetic aperture radar (SAR) image processing, RFI can cause severe degradation of image quality, distortion of polarimetric signatures, and an increase of the SAR phase noise level. To address this issue, a processing system was developed that is capable of reliably detecting, characterizing, and mitigating ... -
Cross-platform application of a sea ice classification method considering incident angle dependency of backscatter intensity and its use in separating level and deformed ice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021)Wide-swath C-band synthetic aperture radar (SAR) has been used for sea ice classification and estimates of sea ice drift and deformation since it first became widely available in the 1990s. Here, we examine the potential to distinguish surface features created by sea ice deformation using ice type classification of SAR data. To perform this task with extended spatial and temporal coverage, we ... -
Data Augmentation for SAR Sea Ice and Water Classification Based on Per-Class Backscatter Variation With Incidence Angle
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-03)Monitoring sea ice in polar regions is critical for understanding global climate change and supporting marine navigation. Recently, researchers started to utilize machine/deep learning methodologies to automate the separation of sea ice and open water in synthetic aperture radar imagery. However, this requires a large amount of reliably labeled training data. We here propose an augmentation routine ... -
The Hotelling-Lawley trace statistic for change detection in polarimetric SAR data under the complex Wishart distribution
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-27)In this paper we propose a new test statistic for unsupervised changedetectioninpolarimetricsyntheticapertureradar(PolSAR) data. We work with multilook complex (MLC) covariance matrix data, whose underlying model is assumed to be the scaled complex Wishart distribution. We use the complex kind Hotelling-Lawley (HL) trace statistic for measuring the similarity of two covariance matrices. The sampling ... -
Imaging Sea Ice Structure by Remote Sensing Sensors
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-14)This paper will investigate how new developments in remote sensing and sensor technologies can be applied to image the structure of the sea ice surface. Both segmentation of multipolarimetric synthetic aperture radar images and strategies for the analyses of polarimetric SAR data of sea ice are addressed. The analysis is based on a Radarsat 2 PolSAR scene of from the Fram Strait in September ... -
Improved LLM Methods Using Linear Regression
(Journal article; Peer reviewed, 2017-12-04)This paper is focused on investigations of the improved correction of the effect of variation in incidence angle on ScanSAR data. Conventional correction methods (such as LLM, locally linear mapping) typically assume that each target class has a similarity distribution in the middle of the image. The objectives of this study are to extend the correction algorithm to full swath width without any ... -
Incident Angle Dependence of Sentinel-1 Texture Features for Sea Ice Classification
(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 ...
