Retrieval of Sea Surface Range Velocities From Envisat ASAR Doppler Centroid Measurements

Hansen, Morten W.; Collard, Fabrice; Dagestad, Knut‐Frode; Johannessen, Johnny A.; Fabry, P.; Chapron, Bertrand

doi:10.1109/tgrs.2011.2153864

Cited by 85 publications

(71 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first step is estimating the Doppler centroid f0 for each range cell [11,[15][16][17][18][19], and then shifting the Doppler spectrum centroid of the single-look complex image to zero. Note that ocean currents can lead to an additional local shift of the Doppler centroid [20][21][22]. However, the Doppler shift resulting from the ocean current is generally less than 5% of the PRF, which can be neglected in the method proposed in this paper.…”

Section: Example 1: Qualitative Analysis For the Estimation Methods Inmentioning

confidence: 99%

See 1 more Smart Citation

Doppler Spectrum-Based NRCS Estimation Method for Low-Scattering Areas in Ocean SAR Images

et al. 2017

View full text Add to dashboard Cite

Abstract:The image intensities of low-backscattering areas in synthetic aperture radar (SAR) images are often seriously contaminated by the system noise floor and azimuthal ambiguity signal from adjacent high-backscattering areas. Hence, the image intensity of low-backscattering areas does not correctly reflect the backscattering intensity, which causes confusion in subsequent image processing or interpretation. In this paper, a method is proposed to estimate the normalized radar cross-section (NRCS) of low-backscattering area by utilizing the differences between noise, azimuthal ambiguity, and signal in the Doppler frequency domain of single-look SAR images; the aim is to eliminate the effect of system noise and azimuthal ambiguity. Analysis shows that, for a spaceborne SAR with a noise equivalent sigma zero (NESZ) of −25 dB and a single-look pixel of 8 m × 5 m, the NRCS-estimation precision of this method can reach −38 dB at a resolution of 96 m × 100 m. Three examples are given to validate the advantages of this method in estimating the low NRCS and the filtering of the azimuthal ambiguity.

show abstract

Section: Example 1: Qualitative Analysis For the Estimation Methods Inmentioning

confidence: 99%

“…Note that ocean currents can lead to an additional local shift of the Doppler centroid [20][21][22]. However, the Doppler shift resulting from the ocean current is generally less than 5% of the PRF, which can be neglected in the method proposed in this paper.…”

Section: Example 1: Qualitative Analysis For the Estimation Methods Inmentioning

confidence: 99%

Doppler Spectrum-Based NRCS Estimation Method for Low-Scattering Areas in Ocean SAR Images

et al. 2017

View full text Add to dashboard Cite

show abstract

“…[7,18] In practice, because of the system and yaw steering errors, the Doppler centroids of the pixels in stripmap SAR image often fluctuate in range but stay stable in azimuth. [22] Thus, in conventional InSAR co-registration, an invariant Doppler centroid (a zero Doppler centroid or a nearly zero Doppler centroid) is used for interpolations generally. As for the cases of acute range Doppler centroids' variations, the range varied Doppler centroids are considered to avoid the interpolation errors.…”

Section: Co-registration Related To 2-d Doppler Centroid Estimationmentioning

confidence: 99%

A novel SAR interferometry processing method in high resolution spotlight SAR

2015

Journal of Electromagnetic Waves and Applications

View full text Add to dashboard Cite

Synthetic Aperture Radar Interferometry (InSAR) can produce accurate Digital Elevation Model (DEM), and a novel spotlight SAR can get higher azimuth resolution than conventional strip-map SAR. Hence, the combination of InSAR and spotlight SAR techniques implies the potential to obtain higher resolution DEMs which will show more tiny terrain variations. However, in spotlight InSAR processing, additional azimuth interferometric fringes and misregistration decorrelation will be induced by conventional co-registration methods which ignore azimuth varied Doppler centroids in interpolations. Meanwhile, because interferometric fringes in regions with high resolution terrain variations can easily be damaged by random phase noise, there will generate more unreliable unwrapped phase areas with conventional phase unwrapping methods. To eliminate residual azimuth fringes, misregistration decorrelation and unreliable unwrapped phase areas, this paper firstly proposes a novel spotlight SAR interferometry processing method based on co-registration related to two-dimensional Doppler centroid estimation and joint phase unwrapping, and it is validated by using TerraSAR-X spotlight data. The final generated 4 m × 4 m grid space DEM not only preserves high resolution, but also has low root mean square error and absolute mean error which are less than 3 m with respect to the Google earth DEM.

show abstract

“…This is caused by the distance and illumination angle of the SAR sensor. The amplitude discontinuities in the range direction correspond to a bias introduced by mispointing of the SAR antenna [27]. The bias produces erroneous variations of the SAR wind speed retrievals but it is expected to be lower than the nominal error of 2 m/s.…”

Section: Deep Water Velocities From S1 Mooringmentioning

confidence: 99%

Correlation between Synthetic Aperture Radar Surface Winds and Deep Water Velocity in the Amundsen Sea, Antarctica

et al. 2013

View full text Add to dashboard Cite

Abstract:The recent observed thinning of the glacier ice shelves in the Amundsen Sea (Antarctica) has been attributed to warm deep currents, possibly induced by along-coast winds in the vicinity of the glacial ice sheet. Here, high resolution maps of wind fields derived from Synthetic Aperture Radar (SAR) data have been studied and correlated with subsurface measurements of the deep water velocities in the Amundsen Sea area. Focus is on periods with low ice coverage in 2010 and 2011. In 2010, which had comparatively low ice coverage, the results indicate a more rapid response to wind forcing in the deep currents than in 2011. The SAR wind speed maps have better spatial resolution than available reanalysis data, and higher maximum correlation was obtained with SAR data than with reanalysis data despite the lower temporal resolution. The maximum correlation was R = 0.71, in a direction that is consistent with wind-driven Ekman theory. This is significantly larger than in previous studies. The larger correlation could be due to the better spatial resolution or the restriction to months with minimum ice coverage. The results indicate that SAR is a useful complement to infer the subsurface variability of the ocean circulation in remote areas in polar oceans. OPEN ACCESSRemote Sens. 2013, 5 4089

show abstract

Retrieval of Sea Surface Range Velocities From Envisat ASAR Doppler Centroid Measurements

Cited by 85 publications

References 27 publications

Doppler Spectrum-Based NRCS Estimation Method for Low-Scattering Areas in Ocean SAR Images

Doppler Spectrum-Based NRCS Estimation Method for Low-Scattering Areas in Ocean SAR Images

A novel SAR interferometry processing method in high resolution spotlight SAR

Correlation between Synthetic Aperture Radar Surface Winds and Deep Water Velocity in the Amundsen Sea, Antarctica

Contact Info

Product

Resources

About