Classification of Compact Polarimetric Synthetic Aperture Radar Images

The RADARSAT Constellation Mission (RCM) was launched in June 2019. RCM, in addition to dual-polarization (DP) and fully quad-polarimetric (QP) imaging modes, provides compact polarimetric (CP) mode data. A CP synthetic aperture radar (SAR) is a coherent DP system in which a single circular polarization is transmitted followed by the reception in two orthogonal linear polarizations. A CP SAR fully characterizes the backscattered field using the Stokes parameters, or equivalently, the complex coherence matrix. This is the main advantage of a CP SAR over the traditional (non-coherent) DP SAR. Therefore, designing scene segmentation and classification methods using CP complex coherence matrix data is advocated in this thesis. Scene classification of remotely captured images is an important task in monitoring the Earth's surface. The high-resolution RCM CP SAR data can be used for land cover classification as well as sea-ice mapping. Mapping sea ice formed in ocean bodies is important for ship navigation and climate change modeling. The Canadian Ice Service (CIS) has expert ice analysts who manually generate sea-ice maps of Arctic areas on a daily basis. An automated sea-ice mapping process that can provide detailed yet reliable maps of ice types and water is desirable for CIS. In addition to linear DP SAR data in ScanSAR mode (500km), RCM wide-swath CP data (350km) can also be used in operational sea-ice mapping of the vast expanses in the Arctic areas. The smaller swath coverage of QP SAR data (50km) is the reason why the use of QP SAR data is limited for sea-ice mapping. This thesis involves the design and development of CP classification methods that consist of two steps: an unsupervised segmentation of CP data to identify homogeneous regions (superpixels) and a labeling step where a ground truth label is assigned to each super-pixel. An unsupervised segmentation algorithm is developed based on the existing Iterative Region Growing using Semantics (IRGS) for CP data and is called CP-IRGS. The constituents of feature model and spatial context model energy terms in CP-IRGS are developed based on the statistical properties of CP complex coherence matrix data. The superpixels generated by CP-IRGS are then used in a graph-based labeling method that incorporates the global spatial correlation among super-pixels in CP data. The classifications of sea-ice and land cover types using test scenes indicate that (a) CP scenes provide improved sea-ice classification than the linear DP scenes, (b) CP-IRGS performs more accurate segmentation than that using only CP channel intensity images, and (c) using global spatial information (provided by a graph-based labeling approach) provides an improvement in classification accuracy values over methods that do not exploit global spatial correlation

Oil Spill Candidate Detection Using a Conditional Random Field Model on Simulated Compact Polarimetric Imagery

This is an Accepted Manuscript of an article published by Taylor & Francis in Canadian Journal of Remote Sensing on 20 April 2022, available online: https://doi.org/10.1080/07038992.2022.2055534Although the compact polarimetric (CP) synthetic aperture radar (SAR) mode of the RADARSAT Constellation Mission (RCM) offers new opportunities for oil spill candidate detection, there has not been an efficient machine learning model explicitly designed to utilize this new CP SAR data for improved detection. This paper presents a conditional random field model based on the Wishart mixture model (CRF-WMM) to detect oil spill candidates in CP SAR imagery. First, a “Wishart mixture model” (WMM) is designed as the unary potential in the CRF-WMM to address the class-dependent information of oil spill candidates and oil-free water. Second, we introduce a new similarity measure based on CP statistics designed as a pairwise potential in the CRF-WMM model so that pixels with strong spatial connections have the same class label. Finally, we investigate three different optimization approaches to solve the resulting maximum a posterior (MAP) problem, namely iterated conditional modes (ICM), simulated annealing (SA), and graph cuts (GC). The results show that our proposed CRF-WMM model can delineate oil spill candidates better than the traditional CRF approaches and that the GC algorithm provides the best optimization.Natural Sciences and Engineering Research Council of Canada (NSERC),Grant RGPIN-2017-04869 || NSERC, Grant DGDND-2017-00078 || NSERC, Grant RGPAS2017-50794 || NSERC, Grant RGPIN-2019-06744

Spatial Modeling of Compact Polarimetric Synthetic Aperture Radar Imagery

The RADARSAT Constellation Mission (RCM) utilizes compact polarimetric (CP) mode to provide data with varying resolutions, supporting a wide range of applications including oil spill detection, sea ice mapping, and land cover analysis. However, the complexity and variability of CP data, influenced by factors such as weather conditions and satellite infrastructure, introduce signature ambiguity. This ambiguity poses challenges in accurate object classification, reducing discriminability and increasing uncertainty. To address these challenges, this thesis introduces tailored spatial models in CP SAR imagery through the utilization of machine learning techniques. Firstly, to enhance oil spill monitoring, a novel conditional random field (CRF) is introduced. The CRF model leverages the statistical properties of CP SAR data and exploits similarities in labels and features among neighboring pixels to effectively model spatial interactions. By mitigating the impact of speckle noise and accurately distinguishing oil spill candidates from oil-free water, the CRF model achieves successful results even in scenarios where the availability of labeled samples is limited. This highlights the capability of CRF in handling situations with a scarcity of training data. Secondly, to improve the accuracy of sea ice mapping, a region-based automated classification methodology is developed. This methodology incorporates learned features, spatial context, and statistical properties from various SAR modes, resulting in enhanced classification accuracy and improved algorithmic efficiency. Thirdly, the presence of a high degree of heterogeneity in target distribution presents an additional challenge in land cover mapping tasks, further compounded by signature ambiguity. To address this, a novel transformer model is proposed. The transformer model incorporates both fine- and coarse-grained spatial dependencies between pixels and leverages different levels of features to enhance the accuracy of land cover type detection. The proposed approaches have undergone extensive experimentation in various remote sensing tasks, validating their effectiveness. By introducing tailored spatial models and innovative algorithms, this thesis successfully addresses the inherent complexity and variability of CP data, thereby ensuring the accuracy and reliability of diverse applications in the field of remote sensing

Quaternary tephrochronology in Iceland dating principles & applications

This thesis presents multi- method numerical ages and age estimates obtained from the previously undated Ókoli Tephra of the Vestfírôir Peninsula, NW Iceland and the Þórsmörk Ignimbrite (ÞIG), Eastern Volcanic Zone, S. Iceland. These provide unique chronological constraints for Quaternary landscape evolution, ice sheet extent and ice -sheet thickness. In addition, they allow ice -free area hypotheses in Iceland to be tested and terrestrial and marine records of palaeoenvironmental change in the North Atlantic region to be linked more securely. The 2.26±0.11 Ma fission-track age of the OÞoli Tephra is particularly important because it places a major new age restriction on glacially driven, macroscale landscape evolution processes of fjord network formation on the Vestfírdir Peninsula.The pre- radiocarbon, Quaternary era is a vital period in which current glacial /interglacial cycles developed and caused widespread environmental change. Dating controls for this era are limited because of widespread glacial erosion, but in Iceland certain tephra deposits have survived glacial overriding and can provide accurate age constraints and precise spatial correlation for stratigraphic sequences. The two tephra deposits chosen for this study are of great palaeoenvironmental significance. The 013oli Tephra rests unconformably 580 -600 m.a.s.l. near the plateau surface of Skagafjall (NW Iceland). The 100 -160 m thick sequence of ice -dammed lake deposits beneath it were thought to have formed `20- 17,000' years ago. The ÞIG (Eastern Volcanic Zone, EVZ, S. Iceland) is the largest Quaternary -age ignimbrite deposit in Iceland and glass compositions have been geochemically linked with the highly silicic (Si0₂ >68 wt %) component of North Atlantic Ash Zone-2 (NAAZ-2), 48-58 ka.Correlation, fission -track (FT) and thermoluminescence (TL) methods were used to produce ages from the glass shards that overwhelmingly dominate the highly silicic airfall and /or pyroclastic flow ash components of these deposits. Dating glass shards is advantageous because they form during the magma -quenching phase of an eruption and nearly always reflect the `true' eruption age. They are also the most far- travelled and geochemically diagnostic phase of Icelandic tephra. Geochemical correlation age estimates were obtained for the Ókoli Tephra and ÞIG by applying multivariate statistical methods to new and published glass -shard data from 104 highly silicic tephra layers /microtephra horizons of Tertiary- Quaternary age from various marine /terrestrial repositories in and around the northern North Atlantic. The isothermal plateau and diameter corrected fission -track (ITPFT & DCFT) methods used are well -established, grain specific, glass -phase dating techniques that produce accurate ages from tephra deposits older than ca. 70 ka. A new coarse -grain (90 -150 gm), glass -phase (2.3 -2.4 gcm⁻³/<2.4 gcm⁻³) TL dating method was developed to take advantage of the glass -rich, phenocryst and micro -inclusion poor nature of the selected deposits. To reconstruct palaeodose values, the established multiple aliquot additive dose TL (MAAD -TL) procedure and an adaptation of a single aliquot regeneration (SAR) luminescence dating procedure, (SAR -TL), that allows continuous assessment of, and correction for, changes in sample TL sensitivity, were used on the Okoli Tephra. The NG, with a ca. 50 ka correlation age estimate, was used as a pseudo -age control for the SAR -TL experiment.Seven correlation age matches ranging from ca. 100 ka -13 Ma were found for the Ókoli Tephra. Composite correlation age matches for the NG are all in the 48.5 -58 ka age range with 48.5 ka the best correlative. Chemical correlation dating is therefore useful in constraining the age of distinctive tephra deposits in the late Pleistocene, but is not always effective over longer timescales. The weighted mean ITPFT/DCFT age of the Ókoli Tephra is 2.26±0.11 Ma and considered accurate. No spontaneous fission tracks were observed for the kirsmórk Ignimbrite, consistent with ca. 50 ka age and glass shard uranium content of 3-4 ppm. The natural SAR -TL signal is located in a second phase of approximately linear dose response growth of the TL signal beyond the first main phase of signal saturation. This meant age estimates greater than the generally quoted 0.8 Ma upper limit of luminescence dating could be calculated. Eight out of eleven TL dating attempts were successful with an age range of 0.6 -4.8 Ma. The weighted mean age from the three successful MAAD -TL runs with a 5 hour, 155°C pre -heat was 2.06 ±0.27 Ma. Longer, low temperature pre -heats (16 hrs, 135°C) reduced age estimates by approximately half. Chánges in TL sensitivity were observed during all SAR -TL experiments restricting age estimates to minimum -maximum age ranges. Nevertheless, the ÓÞoli Tephra SAR -TL age range of 1.74 ±0.37- 4.69±0.74 Ma (pre-heat: 2 minutes, 220°C) encompasses the fission-track age. The natural, glass -phase TL signal of the ÞIG ash is located in the first phase of linear dose response growth before first phase saturation. The minimum -maximum SAR -TL age range is 29 ±7 -40 ±10 ka. The ca. 40 ka maximum SAR -TL age estimate is significantly less than the minimum correlation age estimate, but considered most representative of the geological age because changes in TL sensitivity were greater than for the Ópoli Tephra. The TL methods used need refining, but these results are highly encouraging for developing and applying glass -phase dating procedures across a broader than expected chronological range.The new numerical ages and context of the Ókoli Tephra suggest a proto-fjord network of similar configuration to the current fjord system had formed early in the Quaternary in NW Iceland and that Iceland-wide glacial activity in the first part of the early Pleistocene (2.5-2.0 Ma) was more extensive and /or more widely distributed than previously thought. The Óboli eruption is tentatively linked to the Húsafell volcanic complex on the western mainland and is thought to be one of the first deglaciation induced, massive eruption events of the Pleistocene. The Skagafjall deposits were preserved beneath cold -based non -erosive parts of overriding mid -late Pleistocene ice -sheets. Large TL age errors, caused by uncertain palaeowater content estimates, currently prevent the use of TL dating to establish if the I örsmórk Ignimbrite was deposited by single or multiple eruption events 60 -30 ka. Nevertheless, new ca. 40 ka SAR -TL and 48.5 ka correlation ages of the NG provide a critical 40 -50 ka age constraint on glacial and volcanic processes in the EVZ of southern Iceland. They suggest that volcanic activity in this region was responsible for at least one component of NAAZ -2. The ca. 40 ka SAR -TL dated deposit is an age underestimate or could be the second of at least two discrete 60 -30 ka eruptions in the EVZ of similar magnitude and geochemistry. These eruptions were massive events, possibly triggered by abrupt climatic upturns between 60 -30 ka during the rapidly fluctuating, but generally downward climatic trend towards the LGM

Estimation of the Degree of Polarization in Polarimetric SAR Imagery : Principles and Applications

Les radars à synthèse d’ouverture (RSO) polarimétriques sont devenus incontournables dans le domaine de la télédétection, grâce à leur zone de couverture étendue, ainsi que leur capacité à acquérir des données dans n’importe quelles conditions atmosphériques de jour comme de nuit. Au cours des trois dernières décennies, plusieurs RSO polarimétriques ont été utilisés portant une variété de modes d’imagerie, tels que la polarisation unique, la polarisation double et également des modes dits pleinement polarimétriques. Grâce aux recherches récentes, d’autres modes alternatifs, tels que la polarisation hybride et compacte, ont été proposés pour les futures missions RSOs. Toutefois, un débat anime la communauté de la télédétection quant à l’utilité des modes alternatifs et quant au compromis entre la polarimétrie double et la polarimétrie totale. Cette thèse contribue à ce débat en analysant et comparant ces différents modes d’imagerie RSO dans une variété d’applications, avec un accent particulier sur la surveillance maritime (la détection des navires et de marées noires). Pour nos comparaisons, nous considérons un paramètre fondamental, appelé le degré de polarisation (DoP). Ce paramètre scalaire a été reconnu comme l’un des paramètres les plus pertinents pour caractériser les ondes électromagnétiques partiellement polarisées. A l’aide d’une analyse statistique détaillée sur les images polarimétriques RSO, nous proposons des estimateurs efficaces du DoP pour les systèmes d’imagerie cohérente et incohérente. Ainsi, nous étendons la notion de DoP aux différents modes d’imagerie polarimétrique hybride et compacte. Cette étude comparative réalisée dans différents contextes d’application dégage des propriétés permettant de guider le choix parmi les différents modes polarimétriques. Les expériences sont effectuées sur les données polarimétriques provenant du satellite Canadian RADARSAT-2 et le RSO aéroporté Américain AirSAR, couvrant divers types de terrains tels que l’urbain, la végétation et l’océan. Par ailleurs nous réalisons une étude détaillée sur les potentiels du DoP pour la détection et la reconnaissance des marées noires basée sur les acquisitions récentes d’UAVSAR, couvrant la catastrophe de Deepwater Horizon dans le golfe du Mexique. ABSTRACT : Polarimetric Synthetic Aperture Radar (SAR) systems have become highly fruitful thanks to their wide area coverage and day and night all-weather capabilities. Several polarimetric SARs have been flown over the last few decades with a variety of polarimetric SAR imaging modes; traditional ones are linear singleand dual-pol modes. More sophisticated ones are full-pol modes. Other alternative modes, such as hybrid and compact dual-pol, have also been recently proposed for future SAR missions. The discussion is vivid across the remote sensing society about both the utility of such alternative modes, and also the trade-off between dual and full polarimetry. This thesis contributes to that discussion by analyzing and comparing different polarimetric SAR modes in a variety of geoscience applications, with a particular focus on maritime monitoring and surveillance. For our comparisons, we make use of a fundamental, physically related discriminator called the Degree of Polarization (DoP). This scalar parameter has been recognized as one of the most important parameters characterizing a partially polarized electromagnetic wave. Based on a detailed statistical analysis of polarimetric SAR images, we propose efficient estimators of the DoP for both coherent and in-coherent SAR systems. We extend the DoP concept to different hybrid and compact SAR modes and compare the achieved performance with different full-pol methods. We perform a detailed study of vessel detection and oil-spill recognition, based on linear and hybrid/compact dual-pol DoP, using recent data from the Deepwater Horizon oil-spill, acquired by the National Aeronautics and Space Administration (NASA)/Jet Propulsion Laboratory (JPL) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). Extensive experiments are also performed over various terrain types, such as urban, vegetation, and ocean, using the data acquired by the Canadian RADARSAT-2 and the NASA/JPL Airborne SAR (AirSAR) system

Multifrequency Aperture-Synthesizing Microwave Radiometer System (MFASMR). Volume 1

Background material and a systems analysis of a multifrequency aperture - synthesizing microwave radiometer system is presented. It was found that the system does not exhibit high performance because much of the available thermal power is not used in the construction of the image and because the image that can be formed has a resolution of only ten lines. An analysis of image reconstruction is given. The system is compared with conventional aperture synthesis systems

Polarimetric Synthetic Aperture Radar

This open access book focuses on the practical application of electromagnetic polarimetry principles in Earth remote sensing with an educational purpose. In the last decade, the operations from fully polarimetric synthetic aperture radar such as the Japanese ALOS/PalSAR, the Canadian Radarsat-2 and the German TerraSAR-X and their easy data access for scientific use have developed further the research and data applications at L,C and X band. As a consequence, the wider distribution of polarimetric data sets across the remote sensing community boosted activity and development in polarimetric SAR applications, also in view of future missions. Numerous experiments with real data from spaceborne platforms are shown, with the aim of giving an up-to-date and complete treatment of the unique benefits of fully polarimetric synthetic aperture radar data in five different domains: forest, agriculture, cryosphere, urban and oceans

Comparison of sea-ice freeboard distributions from aircraft data and cryosat-2

The only remote sensing technique capable of obtain- ing sea-ice thickness on basin-scale are satellite altime- ter missions, such as the 2010 launched CryoSat-2. It is equipped with a Ku-Band radar altimeter, which mea- sures the height of the ice surface above the sea level. This method requires highly accurate range measure- ments. During the CryoSat Validation Experiment (Cry- oVEx) 2011 in the Lincoln Sea, Cryosat-2 underpasses were accomplished with two aircraft, which carried an airborne laser-scanner, a radar altimeter and an electro- magnetic induction device for direct sea-ice thickness re- trieval. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a study about the comparison of the sea-ice freeboard and thickness dis- tribution of airborne validation and CryoSat-2 measure- ments within the multi-year sea-ice region of the Lincoln Sea in spring, with respect to the penetration of the Ku- Band signal into the snow