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Registros recuperados: 9
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A labelled ocean SAR imagery dataset of ten geophysical phenomena from Sentinel‐1 wave mode ArchiMer
Wang, Chen; Mouche, Alexis; Tandeo, Pierre; Stopa, Justin; Longépé, Nicolas; Erhard, Guillaume; Foster, Ralph C.; Vandemark, Douglas; Chapron, Bertrand.
The Sentinel‐1 mission is part of the European Copernicus program aiming at providing observations for Land, Marine and Atmosphere Monitoring, Emergency Management, Security and Climate Change. It is a constellation of two (Sentinel‐1 A and B) Synthetic Aperture Radar (SAR) satellites. The SAR wave mode (WV) routinely collects high‐resolution SAR images of the ocean surface during day and night and through clouds. In this study, a subset of more than 37,000 SAR images is labelled corresponding to ten geophysical phenomena, including both oceanic and meteorologic features. These images cover the entire open ocean and are manually selected from Sentinel‐1A WV acquisitions in 2016. For each image, only one prevalent geophysical phenomenon with its prescribed...
Tipo: Text Palavras-chave: Manual labelling; Ocean surface phenomena; Sentinel-1 wave mode; Synthetic aperture radar.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00512/62406/66659.pdf
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Análise de imagens orientada a objetos para integração de imagens SAR e ópticas no mapeamento de áreas periurbanas. Repositório Alice
XAUD, H. A. M.; FONSECA, L. M. da; SANTOS, J. R. dos; GOLTZ, G. A. M.; XAUD, M. R..
2011
Tipo: Artigo em anais de congresso (ALICE) Palavras-chave: Synthetic aperture radar.
Ano: 2011 URL: http://www.alice.cnptia.embrapa.br/handle/doc/989156
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Extraction of coastal ocean wave fields from SAR images ArchiMer
Collard, Fabrice; Ardhuin, Fabrice; Chapron, Bertrand.
Wave spectra derived from synthetic aperture radar (SAR) images acquired by ENVISATs are compared to in situ measurements by seven sensors, deployed in a field experiment carried out on the French coast of La Manche (English Channel). The wave spectra inversion scheme is adapted for shallow water from the European Space Agency (ESA)'s operational processing techniques used for level 2 ocean wave products. Under the low to moderate wind speed observed conditions, overall good agreement is found between in situ and SAR observations over a wide range of wave heights and directions, including waves propagating in the radar azimuth direction and incidence angles different from the standard imagette products.
Tipo: Text Palavras-chave: Synthetic aperture radar; Ocean waves.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-1109.pdf
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Limitation of SAR Quasi-Linear Inversion Data on Swell Climate: An Example of Global Crossing Swells ArchiMer
Jiang, Haoyu; Mouche, Alexis; Wang, He; Babanin, Alexander V.; Chapron, Bertrand; Chen, Ge.
Numerical wave models are powerful tools for investigating global wave climate. Here a global wave hindcast is employed to estimate the global pattern of crossing swells. However, the global patterns of crossing swells derived from the model are different from those derived from the synthetic aperture radar (SAR) wave mode products of quasi-linear inversion, indicating one of them is questionable. The comparison shows that the first two most energetic swells inversed by SAR are often not in accordance with the first two most energetic swells in the model, and this will have a large impact on the statistics of the data. Before this problem is solved, SAR wave products of quasi-linear inversion should be treated with care in wave climate studies.
Tipo: Text Palavras-chave: Synthetic aperture radar; Quasi-linear inversion; Crossing swells; Wave climate.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00369/47979/48003.pdf
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Observations globales des vents et des vagues de surface de l'océan à l'aide de mesures de radars à synthèse d'ouverture spatiaux ArchiMer
Huimin, Li.
Spaceborne synthetic aperture radar (SAR) has been demonstrated invaluable in observing the global ocean winds and waves. SAR images acquired by multiple sensors are employed, including Sentinel-1(S-1), Envisat/ASAR, Gaofen-3 and Radarsat-2. This thesis reviews the commonly used SAR parameters (NRCS and azimuth cutoff) in the first part. A series of calibration steps are required to obtain a proper NRCS and assessment of NRCS is carried out for S-1wave mode (WV). It turns out that WV is poorly calibrated and is thus re-calibrated to obtain accurate NRCS. Azimuth cut off is demonstrated to be complementary to NRCS and can account for the sea state impact on the wind retrieval. Based on the available fully polarimetric SAR products, azimuth cut off is found...
Tipo: Text Palavras-chave: Radar à synthèse d'ouverture; Vents et vagues océaniques; Synthetic aperture radar; Ocean winds; Ocean waves.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00504/61575/65505.pdf
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Partially supervised oil-slick detection by SAR imagery using kernel expansion ArchiMer
Mercier, Grégoire; Ardhuin, Fanny.
Spaceborne synthetic aperture radar (SAR) is well adapted to detect ocean pollution independently from daily or weather conditions. In fact, oil slicks have a specific impact on ocean wave spectra. Initial wave spectra may be characterized by three kinds of waves, namely big, medium, and small, which correspond physically to gravity and gravity-capillary waves. The increase of viscosity, due to the presence of oil damps gravity-capillary waves. This induces not only a damping of the backscattering to the sensor but also a damping of the energy of the wave spectra. Thus, local segmentation of wave spectra may be achieved by the segmentation of a multiscale decomposition of the original SAR image. In this paper, a semisupervised oil-slick detection is...
Tipo: Text Palavras-chave: Water pollution; Synthetic aperture radar; Sea surface; Satellite applications; Oil spill; Image analysis.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1948.pdf
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Preliminary Analysis of Chinese GF-3 SAR Quad-Polarization Measurements to Extract Winds in Each Polarization ArchiMer
Ren, Lin; Yang, Jingsong; Mouche, Alexis; Wang, He; Wang, Juan; Zheng, Gang; Zhang, Huaguo.
This study analyzed the noise equivalent sigma zero (NESZ) and ocean wind sensitivity for Chinese C-band Gaofen-3 (GF-3) quad-polarization synthetic aperture radar (SAR) measurements to facilitate further operational wind extraction from GF-3 data. Data from the GF-3 quad-polarization SAR and collocated winds from both NOAA/NCEP Global Forecast System (GFS) atmospheric model and National Data Buoy Center (NDBC) buoys were used in the analysis. For NESZ, the co-polarization was slightly higher compared to the cross-polarization. Regarding co-polarization and cross-polarization, NESZ was close to RadarSAT-2 and Sentinel-1 A. Wind sensitivity was analyzed by evaluating the dependence on winds in terms of normalized radar cross-sections (NRCS) and polarization...
Tipo: Text Palavras-chave: Gaofen-3; Synthetic aperture radar; Quad-polarization; Ocean surface wind; Noise equivalent sigma zero; Geophysical model function; Polarization ratio; Polarization difference.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00420/53104/54059.pdf
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Rain footprints on C-band synthetic aperture radar images of the ocean - Revisited ArchiMer
Alpers, Werner; Zhang, Biao; Mouche, Alexis; Zeng, Kan; Chan, Pak Wai.
It is well known that rain leaves footprints on the sea surface that sometimes become visible on synthetic aperture radar (SAR) images. Rain cells can easily be detected on SAR images at all radar frequencies when they are associated with a downdraft pattern. But rain cells are not always associated with downdraft and rain can also occur in other forms, as stratified rain, rain bands, and squall lines. It turns out that radar signatures of rain at C-band are much more complex than at L- or X-band radar and that it is particularly difficult to identify unambiguously rain events on C-band SAR images acquired over the ocean. This is because C-band lies in the transition region where raindrops impinging onto the sea surface can increase (usually) or decrease...
Tipo: Text Palavras-chave: Rain over the ocean; Synthetic aperture radar; Sea surface winds; C-band radar backscattering; Ring waves.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00355/46574/46446.pdf
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Strong and highly variable push of ocean waves on Southern Ocean sea ice ArchiMer
Stopa, Justin; Sutherland, Peter; Ardhuin, Fabrice.
Sea ice in the Southern Ocean has expanded over most of the past 20 y, but the decline in sea ice since 2016 has taken experts by surprise. This recent evolution highlights the poor performance of numerical models for predicting extent and thickness, which is due to our poor understanding of ice dynamics. Ocean waves are known to play an important role in ice break-up and formation. In addition, as ocean waves decay, they cause a stress that pushes the ice in the direction of wave propagation. This wave stress could not previously be quantified due to insufficient observations at large scales. Sentinel-1 synthetic aperture radars (SARs) provide high-resolution imagery from which wave height is measured year round encompassing Antarctica since 2014. Our...
Tipo: Text Palavras-chave: Wave-ice interaction; Southern Ocean marginal ice zone; Wave radiation stress; Sentinel-1 SAR; Synthetic aperture radar.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00444/55609/57255.pdf
Registros recuperados: 9
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