SAR imaging of waves in water and ice: Evidence for velocity bunching

Lyzenga, David R.; Shuchman, Robert A.; Lyden, J. D.; Rufenach, C. L.

doi:10.1029/jc090ic01p01031

Cited by 63 publications

(49 citation statements)

References 10 publications

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“…In a linear approximation, can be expressed in terms of the wave spectrum as (3) where is the orbital velocity transfer function given by (4) with incidence angle . Based on (2) and (3), the following integral expression can be derived for a SAR image of a moving sea surface [19] (5) where is the system resolution in the azimuth direction, and and are the spatial coordinates in azimuth and range, respectively. An important property of the transform (5) is that it maintains the mean intensity, i.e., [5].…”

Section: Rementioning

confidence: 99%

“…For deep water, is connected to the wavenumber via the dispersion relation with gravitational acceleration [16]. The modulation of the normalized RCS can then be written as (2) Here, is the RAR MTF, which is governed by different geometrical and hydrodynamic mechanisms [3]. The corresponding analytical expressions used in this study can be found in Appendix A.…”

Section: Rementioning

confidence: 99%

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Measurement of 2-D Sea Surface Elevation Fields Using Complex Synthetic Aperture Radar Data

Schulz‐Stellenfleth

Lehner

2004

IEEE Trans. Geosci. Remote Sensing

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A method is presented to derive two-dimensional sea surface elevation fields from complex synthetic aperture radar (SAR) data. Applied to spaceborne SAR data as acquired by European Remote Sensing 2 (ERS-2) or the Environmental Satellite (ENVISAT), the method allows to analyze the structure of ocean wave fields, e.g., wave grouping or individual wave heights on a global scale. The technique, thus, provides wave parameters not obtained with common SAR wave retrieval schemes, which are designed to estimate the 2-D wave spectrum, i.e., second-order statistical moments of the wave field. Estimates of sea surface elevation fields are obtained based on the existing theory of SAR ocean wave imaging, i.e., the modulation of the SAR image intensity due real aperture radar and motion-related effects. A power series expansion is derived for SAR intensity images that enables the analysis of nonlinear effects as well as to derive a quasi-linear approximation of the SAR imaging model in the spatial domain. A statistical analysis is performed based on a global dataset of 2-D wave spectra provided by the European Centre for Medium-Range Weather Forecast. Distributions are given for the relative error of the quasi-linear approximation in the spatial domain. It is shown that the error can be reduced by smoothing the SAR image in the azimuthal direction at the cost of lower resolution. Smoothed elevation fields are retrieved by the minimization of a cost function defined in the Fourier domain based on the quasi-linear approximation of the imaging process.A multilook technique is applied to infer the information on wave propagation directions, which is required because the SAR transfer function is non-Hermitian, i.e., the SAR image is not determined by the "frozen" sea surface, but wave motion has a significant impact. The method is applied to simulated SAR images as well as to data acquired by ERS-2. The errors of the retrieved wave field due to image noise, uncertainties in the SAR imaging model, and bandwidth limitations are analyzed. In particular, the fact that the estimated elevation field is smoothed due to the finite system resolution and smearing effects associated with wave motion is discussed. A statistical test is proposed to check the homogeneity of the SAR image. The method makes sure that atmospheric effects are not misinterpreted as being caused by ocean waves.

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Section: Rementioning

confidence: 99%

Section: Rementioning

confidence: 99%

Measurement of 2-D Sea Surface Elevation Fields Using Complex Synthetic Aperture Radar Data

Schulz‐Stellenfleth

Lehner

2004

IEEE Trans. Geosci. Remote Sensing

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“…As is known, targets that are moving to the SAR sensor will not be imaged (Lyzenga et al, 1985) is ~ 73 m for TerraSAR-X but almost twice as large, ~ 115 m, for Envisat due to different platform velocity V sar and slant range R o (Envisat altitude was 800 km). Thus, the smoothing of moving wave crests (also called the bunching effect; Alpers and Rufenach, 1979) is noticeably reduced.…”

Section: B Y S U S a N N E L E H N E R A N D R E Y P L E S K A C H mentioning

confidence: 99%

Meteo-Marine Parameters and Their Variability Observed by High Resolution Satellite Radar Images

Lehner¹,

Pleskachevsky²,

Velotto³

et al. 2013

oceanog

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“…• phase shift, or uniform modulations may appear depending on the SAR and wave parameters [420,421]. Because of this non-linearity, it has been suggested that wave information extracted from SAR data is not enough for operational use [436], including the possibility of detecting freak or rogue waves by SAR [438][439][440], claimed to have been observed by ERS-2 wave mode [441,442].…”

Section: Ocean Wavesmentioning

confidence: 99%

Recent Trend and Advance of Synthetic Aperture Radar with Selected Topics

2013

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The present article is an introductory paper in this special issue on synthetic aperture radar (SAR). A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSAR) data, and polarimetric SAR (PolSAR) data. The review is by no means extensive, and as such only brief summaries of of each selected topics and key references are provided. For further details, the readers are recommended to read the literature given in the references theirin.

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SAR imaging of waves in water and ice: Evidence for velocity bunching

Cited by 63 publications

References 10 publications

Measurement of 2-D Sea Surface Elevation Fields Using Complex Synthetic Aperture Radar Data

Measurement of 2-D Sea Surface Elevation Fields Using Complex Synthetic Aperture Radar Data

Meteo-Marine Parameters and Their Variability Observed by High Resolution Satellite Radar Images

Recent Trend and Advance of Synthetic Aperture Radar with Selected Topics

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