SNR-based GNSS reflectometry for coastal sea-level altimetry: results from the first IAG inter-comparison campaign

Geremia‐Nievinski, Felipe; Hobiger, Thomas; Haas, Rüdiger; Liu, Wei; Strandberg, Joakim; Tabibi, Sajad; Vey, Sibylle; Wickert, Jens; Williams, Simon

doi:10.1007/s00190-020-01387-3

Cited by 73 publications

(42 citation statements)

References 62 publications

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“…The latest results from an inter-comparison campaign (Geremia-Nievinski et al 2020) demonstrated an excellent agreement and the capability to derive sea surface heights with a quality of better than 5 cm. Hence, ground-based GNSS-R by means of SNR-analysis seems to be developing into an operational tool for coastal sea-level altimetry, that could possibly reach the quality level of wellestablished observation methods used by conventional tide gauges.…”

Section: Introductionmentioning

confidence: 87%

Revision of the Atmospheric Modeling for SNR Observations in Ground-Based GNSS Reflectometry

Reinking¹

2021

Preprint

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The application of signal-to-noise ratio (SNR) observations from ground-based GNSS Reflectometry is becoming an operational tool for coastal sea-level altimetry. As in all data analyses, systematic influences must be reduced here too, to achieve reliable results. A prominent influence results from atmospheric refraction. Different approaches exist to describe or to correct for this influence. In our contribution we will revise the latest developments and suggest a simple atmospheric interferometric delay model that takes into account ray bending as well as along-path propagation delay. The model takes into account a spherical reflector and can therefore be applied for data from very low elevation angles, too. The findings are double-checked by numerical experiments based on a step-by-step raytracing procedure.

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Section: Introductionmentioning

confidence: 87%

Revision of the Atmospheric Modeling for SNR Observations in Ground-Based GNSS Reflectometry

Reinking¹

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…The latest results from an inter-comparison campaign [7] demonstrated an excellent agreement and the capability to derive sea surface heights with a quality of better than 5 cm. Hence, groundbased GNSS-R by means of SNR-analysis seems to be developing into an operational tool for coastal sea-level altimetry, that could possibly reach the quality level of well-established observation methods used by conventional tide gauges.…”

Section: Introductionmentioning

confidence: 89%

“…Figure 4 shows that we can calculate the interferometric delay in the same way as in the vacuum case, but we do have to take into account the change of the elevation angle and replace e by e+e and in esp by esp+esp in eq. (4), (6) and (7). 4.…”

Section: Atmospheric Ray Pathsmentioning

confidence: 99%

Revision of the Atmospheric Modeling for SNR Observations in Ground-Based GNSS Reflectometry

Reinking¹

2020

Preprint

View full text Add to dashboard Cite

The application of signal-to-noise (SNR) observations from ground-based GNSS Reflectometry is becoming an operational tool for coastal sea-level altimetry. As in all data analyses, systematic influences must be reduced here too, to achieve reliable results. A prominent influence results from atmospheric refraction. Different approaches exist to describe or to correct for this influence. In our contribution we will revise the latest developments and suggest a simple atmospheric interferometric delay model that takes into account ray bending as well as along-path propagation delay. The findings are double-checked by numerical experiments based on a step-by-step raytracing procedure.

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“…A critical aspect is a dependence on the phase of reflections, making inapplicable much of GNSS-R studies developed for incoherent scattering. On the experimental side, about forty existing GNSS stations have been demonstrated for sea-level altimetry (Geremia-Nievinski et al 2020), from which we highlight the first ones and those with the longest duration, as follows. The pioneer was Anderson (2000), after which there was a decade long hiatus, followed by two other demonstrations (Rodriguez-Alvarez et al 2011a;Hongguang et al 2012).…”

Section: Previous Workmentioning

confidence: 99%

An open-source low-cost sensor for SNR-based GNSS reflectometry: design and long-term validation towards sea-level altimetry

et al. 2021

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Monitoring sea level is critical due to climate change observed over the years. Global Navigation Satellite System Reflectometry (GNSS-R) has been widely demonstrated for coastal sea-level monitoring. The use of signal-to-noise ratio (SNR) observations from ground-based stations has been especially productive for altimetry applications. SNR records an interference pattern whose oscillation frequency allows retrieving the unknown reflector height. Here we report the development and validation of a complete hardware and software system for SNR-based GNSS-R. We make it available as open source based on the Arduino platform. It costs about US$200 (including solar power supply) and requires minimal assembly of commercial off-the-shelf components. As an initial validation towards applications in coastal regions, we have evaluated the system over approximately 1 year by the Guaíba Lake in Brazil. We have compared water-level altimetry retrievals with independent measurements from a co-located radar tide gauge (within 10 m). The GNSS-R device ran practically uninterruptedly, while the reference radar gauge suffered two malfunctioning periods, resulting in gaps lasting for 44 and 38 days. The stability of GNSS-R altimetry results enabled the detection of miscalibration steps (10 cm and 15 cm) inadvertently introduced in the radar gauge after it underwent maintenance. Excluding the radar gaps and its malfunctioning periods (reducing the time series duration from 317 to 147 days), we have found a correlation of 0.989 and RMSE of 2.9 cm in daily means. To foster open science and lower the barriers for entry in SNR-based GNSS-R research and applications, we make a complete bill of materials and build tutorials freely available on the Internet so that interested researchers can replicate the system.

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SNR-based GNSS reflectometry for coastal sea-level altimetry: results from the first IAG inter-comparison campaign

Cited by 73 publications

References 62 publications

Revision of the Atmospheric Modeling for SNR Observations in Ground-Based GNSS Reflectometry

Revision of the Atmospheric Modeling for SNR Observations in Ground-Based GNSS Reflectometry

Revision of the Atmospheric Modeling for SNR Observations in Ground-Based GNSS Reflectometry

An open-source low-cost sensor for SNR-based GNSS reflectometry: design and long-term validation towards sea-level altimetry

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