scholarly journals High-rate altimetry in SNR-based GNSS-R: Proof-of-concept of a synthetic vertical array

2021 ◽  
Author(s):  
Mauricio Kenji Yamawaki ◽  
Felipe Geremia-Nievinski ◽  
João Francisco Monico
Keyword(s):  
Sea Level ◽  
Signal To Noise Ratio ◽  
Satellite System ◽  
High Rate ◽  
Proof Of Concept ◽  
Radio Waves ◽  
Vertical Array ◽  
Remote Sensing Technique ◽  
Single Antenna ◽  
Global Navigation Satellite

Global Navigation Satellite System Reflectometry (GNSS-R) has emerged as a promising remote sensing technique for coastal sea level monitoring. The GNSS-R based on signal-to-noise ratio (SNR) observations employs a single antenna and a conventional receiver. It performs best for low elevation satellites, where direct and reflected radio waves are very similar in polarization and direction of arrival. One of the disadvantages of SNR-based GNSS-R for sea level altimetry is its low temporal resolution, which is of the order of one hour for each independent satellite pass. Here we present a proof-of-concept based on a synthetic vertical array. It exploits the mechanical movement of a single antenna at high rate (about 1 Hz). SNR observations can then be fit to a known modulation, of the order of the antenna sweeping rate. We demonstrate that centimetric altimetry precision can be achieved in a 5-minute session. [©2021 IEEE]

scholarly journals High-rate altimetry in SNR-based GNSS-R: Proof-of-concept of a synthetic vertical array

2021 ◽  
Author(s):  
Mauricio Kenji Yamawaki ◽  
Felipe Geremia-Nievinski ◽  
João Francisco Monico
Keyword(s):  
Sea Level ◽  
Signal To Noise Ratio ◽  
Satellite System ◽  
High Rate ◽  
Proof Of Concept ◽  
Radio Waves ◽  
Vertical Array ◽  
Remote Sensing Technique ◽  
Single Antenna ◽  
Global Navigation Satellite

Global Navigation Satellite System Reflectometry (GNSS-R) has emerged as a promising remote sensing technique for coastal sea level monitoring. The GNSS-R based on signal-to-noise ratio (SNR) observations employs a single antenna and a conventional receiver. It performs best for low elevation satellites, where direct and reflected radio waves are very similar in polarization and direction of arrival. One of the disadvantages of SNR-based GNSS-R for sea level altimetry is its low temporal resolution, which is of the order of one hour for each independent satellite pass. Here we present a proof-of-concept based on a synthetic vertical array. It exploits the mechanical movement of a single antenna at high rate (about 1 Hz). SNR observations can then be fit to a known modulation, of the order of the antenna sweeping rate. We demonstrate that centimetric altimetry precision can be achieved in a 5-minute session. [©2021 IEEE]

Comparison of high rate GNSS and GNSS-R measurements for detecting tidal bores in the Garonne River

2020 ◽  
Author(s):  
Pierre Zeiger ◽  
José Darrozes ◽  
Frédéric Frappart ◽  
Guillaume Ramillien ◽  
Laurent Lestarquit ◽  
...  
Keyword(s):  
Sea Level ◽  
Sampling Rate ◽  
Acoustic Doppler Current Profiler ◽  
Satellite System ◽  
High Rate ◽  
Tidal Bore ◽  
Garonne River ◽  
Current Profiler ◽  
Oceanic Tides ◽  
Global Navigation Satellite

<p>The Reflected Global Navigation Satellite System (GNSS-R) is a bi-static radar system in which the receiver collect GNSS signals reflected from the Earth surface and compares them with corresponding direct signals. Measurements can be performed on the waveforms to determine the elevation of the free surface, leading to applications such as ocean altimetry, inland water level variations, soil moisture, snow depth and atmospheric water changes. This study presents the potential of in-situ GNSS-R for tidal bore detection and characterization, and compares it to high rate GNSS observations and other reference datasets.</p><p>The data we used were acquired on 17<sup>th</sup> and 18<sup>th</sup> October 2016 in the Garonne River, at 126 km upstream the mouth of the Gironde estuary. We processed GNSS-based elevations from data acquired on a buoy at a 20 Hz sampling rate using differential GNSS (DGNSS) technique. Acoustic Doppler Current Profiler (ADCP) measurements as well as pressure data were used for validation purposes. These techniques show good results in estimating the amplitude of the first wave, the period of the tidal bore and the oceanic tides. All of these datasets were compared to the retrieval of GNSS-R signals above the river. We have processed the changes in water height throughout the acquisition using <em>Larson et al.</em> (2013) and <em>Roussel et al.</em> (2015) techniques. We finally separate the atmospheric component from the tidal bore and the oceanic tides ones.</p><p> </p><p>Larson, K. M., Löfgren, J. S., and Haas, R. (2013). Coastal sea level measurements using a single geodetic gps receiver. Advances in Space Research, 51(8):1301–1310.</p><p>Roussel, N., Ramillien, G., Frappart, F. et al. (2015). Sea level monitoring and sea state estimate using a single geodetic receiver. Remote Sensing of Environment, 171:261 – 277.</p>

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

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
M. A. R. Fagundes ◽  
I. Mendonça-Tinti ◽  
A. L. Iescheck ◽  
D. M. Akos ◽  
F. Geremia-Nievinski
Keyword(s):  
Open Source ◽  
Sea Level ◽  
Tide Gauge ◽  
Signal To Noise Ratio ◽  
Low Cost ◽  
Satellite System ◽  
Open Science ◽  
Coastal Sea ◽  
Commercial Off The Shelf ◽  
Global Navigation Satellite

AbstractMonitoring 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.

Performance Assessment of GNSS-R Polarimetric Observations for Sea Level Monitoring

2021 ◽  
Author(s):  
Mahmoud Rajabi ◽  
Mstafa Hoseini ◽  
Hossein Nahavandchi ◽  
Maximilian Semmling ◽  
Markus Ramatschi ◽  
...  
Keyword(s):  
Time Series ◽  
Circular Polarization ◽  
Sea Level ◽  
Tide Gauge ◽  
Satellite System ◽  
Sea Surface ◽  
Analysis Tool ◽  
Lower Accuracy ◽  
Coastal Sea ◽  
Global Navigation Satellite

<p>Determination and monitoring of the mean sea level especially in the coastal areas are essential, environmentally, and as a vertical datum. Ground-based Global Navigation Satellite System Reflectometry (GNSS-R) is an innovative way which is becoming a reliable alternative for coastal sea-level altimetry. Comparing to traditional tide gauges, GNSS-R can offer different parameters of sea surface, one of which is the sea level. The measurements derived from this technique can cover wider areas of the sea surface in contrast to point-wise observations of a tide gauge.  </p><p>We use long-term ground-based GNSS-R observations to estimate sea level. The dataset includes one-year data from January to December 2016. The data was collected by a coastal GNSS-R experiment at the Onsala space observatory in Sweden. The experiment utilizes three antennas with different polarization designs and orientations. The setup has one up-looking, and two sea-looking antennas at about 3 meters above the sea surface level. The up-looking antenna is Right-Handed Circular Polarization (RHCP). The sea-looking antennas with RHCP and Left-Handed Circular Polarization (LHCP) are used for capturing sea reflected Global Positioning System (GPS) signals. A dedicated reflectometry receiver (GORS type) provides In-phase and Quadrature (I/Q) correlation sums for each antenna based on the captured interferometric signal. The generated time series of I/Q samples from different satellites are analyzed using the Least Squares Harmonic Estimation (LSHE) method. This method is a multivariate analysis tool which can flexibly retrieve the frequencies of a time series regardless of possible gaps or unevenly spaced sampling. The interferometric frequency, which is related to the reflection geometry and sea level, is obtained by LSHE with a temporal resolution of 15 minutes. The sea level is calculated based on this frequency in six modes from the three antennas in GPS L1 and L2 signals.</p><p>Our investigation shows that the sea-looking antennas perform better compared to the up-looking antenna. The highest accuracy is achieved using the sea-looking LHCP antenna and GPS L1 signal. The annual Root Mean Square Error (RMSE) of 15-min GNSS-R water level time series compared to tide gauge observations is 3.7 (L1) and 5.2 (L2) cm for sea-looking LHCP, 5.8 (L1) and 9.1 (L2) cm for sea-looking RHCP, 6.2 (L1) and 8.5 (L2) cm for up-looking RHCP. It is worth noting that the GPS IIR block satellites show lower accuracy due to the lack of L2C code. Therefore, the L2 observations from this block are eliminated.</p>

scholarly journals Potential Applications of GNSS-R Observations over Agricultural Areas: Results from the GLORI Airborne Campaign

2018 ◽  
Vol 10 (8) ◽  
pp. 1245 ◽  
Author(s):  
Mehrez Zribi ◽  
Erwan Motte ◽  
Nicolas Baghdadi ◽  
Frédéric Baup ◽  
Sylvia Dayau ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Signal To Noise Ratio ◽  
Soil Surface ◽  
Satellite System ◽  
Area Index ◽  
Vegetation Height ◽  
Study Sites ◽  
Global Navigation Satellite ◽  
Vegetation Characteristic ◽  
Agricultural Areas

The aim of this study is to analyze the sensitivity of airborne Global Navigation Satellite System Reflectometry (GNSS-R) on soil surface and vegetation cover characteristics in agricultural areas. Airborne polarimetric GNSS-R data were acquired in the context of the GLORI’2015 campaign over two study sites in Southwest France in June and July of 2015. Ground measurements of soil surface parameters (moisture content) and vegetation characteristics (leaf area index (LAI), and vegetation height) were recorded for different types of crops (corn, sunflower, wheat, soybean, vegetable) simultaneously with the airborne GNSS-R measurements. Three GNSS-R observables (apparent reflectivity, the reflected signal-to-noise-ratio (SNR), and the polarimetric ratio (PR)) were found to be well correlated with soil moisture and a major vegetation characteristic (LAI). A tau-omega model was used to explain the dependence of the GNSS-R reflectivity on both the soil moisture and vegetation parameters.

scholarly journals Investigation of the Occurrence of Nighttime Topside Ionospheric Irregularities in Low-Latitude and Equatorial Regions Using CYGNSS Satellites

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 708 ◽  
Author(s):  
Liang Huang ◽  
Yi Liu ◽  
Qiong Tang ◽  
Guanyi Chen ◽  
Zhuangkai Wang ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Global Analysis ◽  
Satellite System ◽  
Ionospheric Irregularities ◽  
Wave Number ◽  
Significant Finding ◽  
Low Latitude ◽  
Zonal Wave Number ◽  
Global Navigation Satellite ◽  
Maximum Occurrence

By using multi-satellite observations of the L1 signal-to-noise ratio (SNR) from the Cyclone Global Navigation Satellite System (CYGNSS) taken in 2017, we present the occurrence of nighttime topside ionospheric irregularities in low-latitude and equatorial regions. The most significant finding of this study is the existence of longitudinal structures with a wavenumber 4 pattern in the topside irregularities. This suggests that lower atmospheric waves, especially a daytime diurnal eastward-propagating zonal wave number-3 nonmigrating tide (DE3), might play an important role in the generation of topside plasma bubbles during the low solar minimum. Observations of scintillation events indicate that the maximum occurrence of nighttime topside ionospheric irregularities occurs on the magnetic equator during the equinoxes. The current work, which could be regarded as an important update of the previous investigations, would be readily for the further global analysis of the topside ionospheric irregularities.

scholarly journals A Joint Method Based on Time-Frequency Distribution to Detect Time-Varying Interferences for GNSS Receivers with a Single Antenna

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1946 ◽  
Author(s):  
Qingshui Lv ◽  
Honglei Qin
Keyword(s):  
Hough Transform ◽  
Frequency Estimation ◽  
Satellite System ◽  
Time Varying ◽  
Actual Performance ◽  
Time Frequency ◽  
Single Antenna ◽  
Global Navigation Satellite ◽  
Mean Square Errors ◽  
Joint Method

In this paper, a joint method combining Hough transform and reassigned smoothed pseudo Wigner-Ville distribution (RSPWVD) is presented to detect time-varying interferences with crossed frequency for a Global Navigation Satellite System (GNSS) receiver with a single antenna. The proposed method can prevent the cross-term interference and detect the time-varying interferences with crossed frequency which cannot be achieved by the classical time-frequency (TF) analysis with the peak detection method. The actual performance of the developed method has been evaluated by experiments with conditions where the real BeiDou system (BDS) B1I signals are corrupted by the simulated chirp interferences. The results of experiments show that the introduced method is effectively able to detect chirp interferences with crossed frequency and provide the same root mean square errors (RMSE) of the parameter estimation for chirp one and the improved initial frequency estimation for chirp two compared with the Hough transform of Wigner-Ville distribution (WVD) when the jamming to noise ratio (JNR) equals or surpasses 4 dB.

scholarly journals Tracking of geodetic height of sea level in the west of Java Sea, Indonesia: A preliminary assessment

2019 ◽  
Vol 94 ◽  
pp. 01003 ◽  
Author(s):  
Poerbandono ◽  
Kosasih Prijatna ◽  
Irwan Gumilar
Keyword(s):  
Sea Level ◽  
Global Navigation Satellite System ◽  
Satellite System ◽  
Careful Examination ◽  
Navigation Satellite ◽  
The West ◽  
Geodetic Height ◽  
Java Sea ◽  
Global Navigation ◽  
Global Navigation Satellite

This paper assesses the agreement between observed heights of sea level from Global Navigation Satellite System (GNSS) and a global model of Mean Sea Surface (MSS). The assessment of the agreement is carried out according to the direct comparison between the height of MSS model and the geodetic height of actual sea level. Here, MSS is generated according to Gravity Recovery And Climate Experiment (GRACE) Gravity Model (GGM) and Mean Dynamic Ocean Topography (MDOT). The tracking of geodetic heights of actual sea level are done by Wide Area Differential (WA D) and Real Time Precise Point Positioning (RTPPP) Global Navigation Satellite System (GNSS) along an approximately 180 Nm SW-NE transect of away-return ship track in the west of the Java Sea, Indonesia. It is found that the overall agreement between geodetic height of sea level and MSS observed by WA DGNSS is 7.5 cm (away tracking), while those observed by RTPPP GNSS is 39.5 cm (away tracking) and 36.0 cm (return tracking). This work recommends selection of the best-fit tide model and careful examination on the dynamics of antenna offset due to vessel attitude.

Experimental results of multipath behavior for GPS L1-L2 and Galileo E1-E5b in static and kinematic scenarios

2019 ◽  
Vol 13 (4) ◽  
pp. 279-289 ◽  
Author(s):  
Alexandra Avram ◽  
Volker Schwieger ◽  
Noha El Gemayel
Keyword(s):  
Signal To Noise Ratio ◽  
Measurement Data ◽  
Absolute Error ◽  
Autonomous Driving ◽  
Satellite System ◽  
Natural Environments ◽  
Navigation Systems ◽  
Global Navigation Satellite ◽  
The Impact ◽  
Measurement Campaigns

Abstract Current trends like Autonomous Driving (AD) increase the need for a precise, reliable, and continuous position at high velocities. In both natural and man-made environments, Global Navigation Satellite System (GNSS) signals suffer challenges such as multipath, attenuation, or loss-of-lock. As Highway Assist and Highway Pilot are AD next steps, multipath knowledge is necessary for this typical user-case and kinematic situations. This paper presents a multipath performance analysis for GPS and Galileo satellites in static, slow, and high kinematic scenarios. The data is provided from car test-drives in both controlled and unrestricted, near-natural environments. The Code-Minus-Carrier (CMC) and cycle-slip implementations are validated with measurement data from consecutive days. Multipath statistical models based on satellite elevation are evaluated for the three investigated scenarios. Static models derived from the car setup measurements for GPS L1, L2 and Galileo E1 and E5b show a good agreement with a state-of-the-art model as well as the enhanced Galileo signals performance. Slow kinematic multipath results in a controlled environment showed an improvement for both navigation systems compared to the static measurements at the same place. This result is confirmed by static and slow kinematic multipath simulations with the same GNSS receiver. Post-processing analysis on highway measurements revealed a bigger multipath bias, compared to the open-sky static and slow kinematic measurement campaigns. Although less critical as urban or rural, this indicates the presence of multipath in this kind of environment as well. The impact of different parameters, including receiver architecture and Signal-to-noise ratio (SNR) are analyzed and discussed. Differential position (DGNSS) based on code is computed for each epoch and compared against GNSS/INS integrated position for all three measurement campaigns. The most significant 3D absolute error occurs where the greatest multipath envelope is found.

scholarly journals Rupture kinematics of 2020 January 24 Mw 6.7 Doğanyol-Sivrice, Turkey earthquake on the East Anatolian Fault Zone imaged by space geodesy

2020 ◽  
Vol 223 (2) ◽  
pp. 862-874 ◽  
Author(s):  
Diego Melgar ◽  
Athanassios Ganas ◽  
Tuncay Taymaz ◽  
Sotiris Valkaniotis ◽  
Brendan W Crowell ◽  
...  
Keyword(s):  
Fault Zone ◽  
Satellite System ◽  
High Rate ◽  
Slip Model ◽  
Slip Region ◽  
Global Navigation Satellite ◽  
Rupture Kinematics ◽  
Source Duration ◽  
East Anatolian Fault Zone ◽  
East Anatolian Fault

SUMMARY Here, we present the results of a kinematic slip model of the 2020 Mw 6.7 Doğanyol-Sivrice, Turkey Earthquake, the most important event in the last 50 yr on the East Anatolian Fault Zone. Our slip model is constrained by two Sentinel-1 interferograms and by 5 three-component high-rate GNSS (Global Navigation Satellite System) recordings close to the earthquake source. We find that most of the slip occurs predominantly in three regions, two of them at between 2 and 10 km depth and a deeper slip region extending down to 20 km depth. We also relocate the first two weeks of aftershocks and find a distribution of events that agrees with these slip features. The HR-GNSS recordings suggest a predominantly unilateral rupture with the effects of a directivity pulse clearly seen in the waveforms and in the measure peak ground velocities. The slip model supports rupture propagation from northeast to southwest at a relatively slow speed of 2.2 km s−1 and a total source duration of ∼20 s. In the absence of near-source seismic stations, space geodetic data provide the best constraint on the spatial distribution of slip and on its time evolution.

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