Ocean Surface's Scattering Coefficient Retrieval by Delay–Doppler Map Inversion

Valencia, E.; Camps, A.; Marchan-Hernandez, J.F.; Park, Hyuk; Bosch-Lluis, X.; Rodriguez-Alvarez, Nereida; Ramos-Perez, I.

doi:10.1109/lgrs.2011.2107500

Cited by 55 publications

(47 citation statements)

References 12 publications

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“…A GNSS-R instrument can be understood as a bistatic Synthetic Aperture Radar (SAR) using navigation signals as sources of opportunity with a very short integration time, as limited by the coherent integration time (typically TR iR1 ms), followed by long incoherent averaging so as to reduce speckle noise (typically NR incohR ranges from 1000 to 10000, corresponding to 1-10 s total integration) [24]. As for low-resolution SAR sensors (the case of GNSS-R instruments), the number of scatterers in the resolution cell is very large, 1 T the statistics of SAR images follow the predictions of the Rayleigh model, and the Exponential model matches well the actual data (e.g., [25]).…”

Section: Discussionmentioning

confidence: 99%

Time-domain Statistics of the Electromagnetic Bias in GNSS-Reflectometry

Ghavidel

Camps

2015

Remote Sensing

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Global Navigation Satellite Systems-Reflectometry (GNSS-R) is an emerging remote sensing technique that uses navigation signals reflected on the Earth's surface as sources of opportunity for scatterometry and altimetry. The time-domain statistics of the electromagnetic bias in GNSS-R altimetry are investigated to assess the residual electromagnetic bias after averaging during the dwell time (as long as 100 s). A three-dimensional time-evolving sea surface is generated using Elfouhaily's ocean surface height spectrum and spreading function. This surface is illuminated by a right hand circular polarization electromagnetic wave at L-band. Then, the scattered waves are computed using the Physical Optics method under the Kirchhoff Approximation. The electromagnetic bias is estimated using a numerical technique previously validated at C-and Ku-bands, and then extrapolated at L-band. Montecarlo simulations for different sea surface realizations consecutive in time are performed so as to analyze the electromagnetic bias statistics up to the 4P th P order moments. Histograms and distribution of the time domain electromagnetic bias are also used for statistical interpretation. All statistical descriptors confirmed that the electromagnetic bias has a non-Gaussian behavior. This study is important to assess the residual electromagnetic bias in future GNSS-R altimetry missions, such as the "GNSS Reflectometry, Radio Occultation and Scatterometry on board the International Space Station" experiment onboard the International Space Station. OPEN ACCESSRemote Sens. 2015, 7 11152

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Section: Discussionmentioning

confidence: 99%

Time-domain Statistics of the Electromagnetic Bias in GNSS-Reflectometry

Ghavidel

Camps

2015

Remote Sensing

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“…The main idea of the method is directly restoring the scattering coefficient from the DDMs using the DDM deconvolution proposed in [7], and then computing the PDF of the surface slope using (3). Eventually the wind state can be retrieved by using the relationship between wind state and the features of slope PDF.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, Valencia et al have proposed scattering coefficient retrieval method from the DDM [7]. Based on the scattering coefficients restored using the method in [7], a new approach to retrieve the wind speed is proposed in this study.…”

Section: Introductionmentioning

confidence: 99%

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New approach to sea surface wind retrieval from GNSS-R measurements

Park

Valencia

Rodriguez-Alvarez

et al. 2011

2011 IEEE International Geoscience and Remote Sensing Symposium

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So far, GNSS-R studies on sea surface wind retrieval from Delay-Doppler Maps (DDM) have focused on the best fitting of the model to the measurements. This paper proposes a new approach to retrieve the sea surface wind using DDM deconvolution. The proposed method is based on the direct restoration of scattering coefficients from two measured DDMs. Using the restored scattering coefficient images, the sea surface slope is estimated, and eventually the wind speed is retrieved from the sea surface slope. This paper presents the performance of the proposed method with the simulation results, and the advantages of the method.

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“…So far, one of the main applications of GNSS-R is sea state estimation and monitoring, and several approaches and techniques to estimate the local wind speed from GNSS-R observables have been developed in the last years [16]- [19]. Other very recent applications of the GNSS-R technology concern the surface scattering coefficient retrieval [20], [21], ocean topography [22], oil slick detection [23], [24], and tsunami detection [25], [26]. Due to the absence of a transmitter module, GNSS-R payloads can be mounted on nano-or small-satellites-as the recently launched 3 Cat-2 satellite by UPC [27]-with the potential to be deployed in wide constellations.…”

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confidence: 99%

Sea Target Detection Using Spaceborne GNSS-R Delay-Doppler Maps: Theory and Experimental Proof of Concept Using TDS-1 Data

Simone

Park

Riccio

et al. 2017

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Abstract-This study addresses a novel application of global navigation satellite system-reflectometry (GNSS-R) delay-Doppler maps (DDMs), namely sea target detection. In contrast with other competing remote sensing technologies, such as synthetic aperture radar and optical systems, typically exploited in the field of sea target detection, GNSS-R systems could be employed as satellite constellations, so as to fulfill the temporal requirements for near real-time ships and sea ice sheets monitoring. In this study, the revisit time offered by GNSS-R systems is quantitatively evaluated by means of a simulation analysis, in which three different realistic GNSS-R missions are simulated and analyzed. Then, a sea target detection algorithm from spaceborne GNSS-R DDMs is described and assessed. The algorithm is based on a sea clutter compensation step and uses an adaptive threshold to take into account spatial variations in the sea background and/or noise statistics. Finally, the sea target detector algorithm is tested and validated for the first time ever using experimental GNSS-R data from the U.K. TechDemoSat-1 dataset. Performance is assessed by providing the receiver operating characteristic curves, and some preliminary experimental results are presented.Index Terms-Constant false alarm rate (CFAR), global navigation satellite system-reflectometry (GNSS-R), maritime surveillance, sea state, sea target detection.

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Ocean Surface's Scattering Coefficient Retrieval by Delay–Doppler Map Inversion

Cited by 55 publications

References 12 publications

Time-domain Statistics of the Electromagnetic Bias in GNSS-Reflectometry

Time-domain Statistics of the Electromagnetic Bias in GNSS-Reflectometry

New approach to sea surface wind retrieval from GNSS-R measurements

Sea Target Detection Using Spaceborne GNSS-R Delay-Doppler Maps: Theory and Experimental Proof of Concept Using TDS-1 Data

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