Altimetric Analysis of the Sea-Surface GPS-Reflected Signals

Rius, A.; Cardellach, Estel; Martín-Neira, Manuel

doi:10.1109/tgrs.2009.2036721

Cited by 145 publications

(110 citation statements)

References 15 publications

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“…As for airborne altimetry a few kilometres or spaceborne altimetry of several hundreds of kilometres above the sea, the displacement between time point of the peak of the cross-correlation and that of the delay can be significant. To determine the true delay of the signal reflected at the specular point, the derivative of the delay waveforms can be exploited (Hajj & Zuffada 2003, Rius et al 2010. That is, the time point of the peak of the derivative of the waveform corresponds to the delay of the reflected signal.…”

Section: Fundamentalsmentioning

confidence: 99%

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Sea Surface Altimetry Based on Airborne GNSS Signal Measurements

Rizos

Dempster

2012

ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:In this study the focus is on ocean surface altimetry using the signals transmitted from GNSS (Global Navigation Satellite System) satellites. A low-altitude airborne experiment was recently conducted off the coast of Sydney. Both a LiDAR experiment and a GNSS reflectometry (GNSS-R) experiment were carried out in the same aircraft, at the same time, in the presence of strong wind and rather high wave height. The sea surface characteristics, including the surface height, were derived from processing the LiDAR data. A two-loop iterative method is proposed to calculate sea surface height using the relative delay between the direct and the reflected GNSS signals. The preliminary results indicate that the results obtained from the GNSS-based surface altimetry deviate from the LiDAR-based results significantly. Identification of the error sources and mitigation of the errors are needed to achieve better surface height estimation performance using GNSS signals.

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Section: Fundamentalsmentioning

confidence: 99%

“…Bridge-based experiments were reported by Rius et al (2011). Airborne experiments were carried out and reported by Lowe et al (2002) and Rius et al (2010). Results of ESA's spaceborne PARIS experiments and altimeter in-orbit demonstrator were reported by Martin-Neira et al (2011).…”

Section: Introductionmentioning

confidence: 99%

Sea Surface Altimetry Based on Airborne GNSS Signal Measurements

Rizos

Dempster

2012

ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci.

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“…On the other hand, upcoming GNSS-R altimeters use a bistatic (off-nadir) configuration, much lower transmitted power, narrower bandwidth 3 , and use frequency bands allocated for radionavigation 4 .…”

Section: Introductionmentioning

confidence: 99%

Numerical Computation of the Electromagnetic Bias in GNSS-R Altimetry

Ghavidel

Schiavulli

Camps

2016

IEEE Trans. Geosci. Remote Sensing

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In radar altimetry the electromagnetic (EM) bias is originated by the smaller reflectivity of wave crests than troughs, thus the average sea surface height is under-estimated. Bias uncertainty is currently the largest factor in altimetry error budgets. The EM bias in a bistatic forward-scattering configuration at L-band, such as in Global Navigation Satellite SystemsReflectometry (GNSS-R) altimetry, remains one of the major sources of uncertainty in the altimetry error budget. In this work the EM bias is computed using numerical simulations.To do so, a time-dependent synthetic non-Gaussian sea surface is created using the PiersonMoskowitz and Elfouhaily sea surface height spectra and spreading function. The sea surface is then discretized in facets and "illuminated" using a Right Hand Circular Polarization data at C-and Ku-bands. Then, the numerical model is applied at L-band, for bistatic configurations, including different azimuth angles, and different wind speeds. It is found that the EM bias is almost insensitive to the sea surface spectra selected and increases with increasing wind speed and incidence/scattering angle (up to ~20 cm at θi,s = 45° and U10 = 12 m/s), and it also exhibits a non-negligible azimuthal dependence, that must be accounted for in the error budgets of upcoming GNSS-R altimetry missions.

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“…This technique, also known as GNSS-Reflectometry (GNSS-R), can provide a dense spatial and temporal sampling capability over the Earth surface in a low-cost way. During the past two decades, several theoretical and experimental studies have been performed to demonstrate the feasibility of ocean altimetry using reflected GNSS signals, e.g., in [2][3][4][5][6][7][8][9], and several studies have been performed on scatterometric applications, such as sea surface wind, sea ice and soil moisture. A comprehensive tutorial of GNSS-R technique and its applications can be found in [10].…”

Section: Introductionmentioning

confidence: 99%

The Impact of Inter-Modulation Components on Interferometric GNSS-Reflectometry

Rius

Fabra

et al. 2016

Remote Sensing

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Abstract:The interferometric Global Navigation Satellite System Reflectometry (iGNSS-R) exploits the full spectrum of the transmitted GNSS signal to improve the ranging performance for sea surface height applications. The Inter-Modulation (IM) component of the GNSS signals is an additional component that keeps the power envelope of the composite signals constant. This extra component has been neglected in previous studies on iGNSS-R, in both modelling and instrumentation. This letter takes the GPS L1 signal as an example to analyse the impact of the IM component on iGNSS-R ocean altimetry, including signal-to-noise ratio, the altimetric sensitivity and the final altimetric precision. Analytical results show that previous estimates of the final altimetric precision were underestimated by a factor of 1.5∼1.7 due to the negligence of the IM component, which should be taken into account in proper design of the future spaceborne iGNSS-R altimetry missions.

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Altimetric Analysis of the Sea-Surface GPS-Reflected Signals

Cited by 145 publications

References 15 publications

Sea Surface Altimetry Based on Airborne GNSS Signal Measurements

Sea Surface Altimetry Based on Airborne GNSS Signal Measurements

Numerical Computation of the Electromagnetic Bias in GNSS-R Altimetry

The Impact of Inter-Modulation Components on Interferometric GNSS-Reflectometry

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