Feasibility analysis of GNSS-based ionospheric observation on a fast-moving train platform (GIFT)

AbstractThe ionospheric effect plays a crucial role in the radio communications. For ionospheric observing and monitoring, the Global Navigation Satellite System (GNSS) has been widely utilized. The ionospheric condition can be characterized by the Total Electron Contents (TEC) and TEC Rate (TECR) calculated from the GNSS measurements. Currently, GNSS-based ionospheric observing and monitoring largely depend on a global fiducial network of GNSS receivers such as the International GNSS Service (IGS) network. We propose a new approach to observe the ionosphere by deploying a GNSS receiver on a Hong Kong Mass Transit Railway (MTR) train. We assessed the TECR derived from the MTR-based GNSS receiver by comparing it with the TECR derived from a static GNSS receiver. The results show that the Root-Mean-Squares (RMS) errors of the TECR derived from the MTR-based GNSS receiver is consistently approximately 23% higher than that derived from the static GNSS receiver. Despite the increased error, the findings suggest that the GNSS observation on a fast-moving platform is a feasible approach to observe the ionosphere over a large region in a rapid and cost-effective way.

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MONITORING OF IONOSPHERIC SCINTILLATION PHENOMENA USING SYNTHETIC APERTURE RADAR (SAR)

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-iv-5-331-2018 ◽

2018 ◽

Vol IV-5 ◽

pp. 331-337

Author(s):

S. Mohanty ◽

C. Carrano ◽

G. Singh

Keyword(s):

Satellite System ◽

Synthetic Aperture ◽

Ionospheric Scintillation ◽

Electron Content ◽

Data Sets ◽

Low Frequencies ◽

Total Electron ◽

Gnss Receiver ◽

Synthetic Aperture Radars ◽

Global Navigation Satellite

Abstract. The applications of synthetic aperture radars (SAR) have increased manifold in the past decade, which includes numerous Earth observation applications such as agriculture, forestry, disaster monitoring cryospheric- and atmospheric- studies. Among them, the potential of SAR for ionospheric studies is gaining importance. The susceptibility of SAR to space weather dynamics, and ionosphere in particular, comes at low frequencies of L- and P-bands. This paper discusses one such scintillation event that was observed by L-band Advanced Land Observation Satellite (ALOS)-2 Phased Array L-type SAR (PALSAR) over southern India on March 23, 2015. The sensors also acquired data sets on four other days on which the ionosphere was quiet. Ionospheric parameter measurements of total electron content (TEC) and amplitude scintillation (S4) index from ground-based Global Navigation Satellite System (GNSS) receiver at Tirunelveli was used to establish the ionospheric conditions on the days of SAR acquisition as well as to corroborate the S4 estimated from SAR. Multi-temporal ALOS-2 data sets were utilized to calculate S4 from two separate methods and the results have a good agreement with GNSS receiver measurements. This highlights the potential of SAR as an alternate technique of monitoring ionospheric scintillations that can be utilized as complementary to the highly accurate and dedicated measurements from the GNSS networks.

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Correlation between Ionospheric TEC and the DCB Stability of GNSS Receivers from 2014 to 2016

Remote Sensing ◽

10.3390/rs11222657 ◽

2019 ◽

Vol 11 (22) ◽

pp. 2657 ◽

Cited By ~ 4

Author(s):

Choi ◽

Sohn ◽

Lee

Keyword(s):

Estimation Method ◽

Satellite System ◽

Electron Content ◽

Strong Positive Correlation ◽

Low Latitude ◽

Total Electron ◽

Gnss Receiver ◽

Gnss Receivers ◽

Global Navigation Satellite ◽

The Relationship

The Global Navigation Satellite System (GNSS) differential code biases (DCBs) are a major obstacle in estimating the ionospheric total electron content (TEC). The DCBs of the GNSS receiver (rDCBs) are affected by various factors such as data quality, estimation method, receiver type, hardware temperature, and antenna characteristics. This study investigates the relationship between TEC and rDCB, and TEC and rDCB stability during a three-year period from 2014 to 2016. Linear correlations between pairs of variables, measured with Pearson’s coefficient (), are considered. It is shown that the correlation between TEC and rDCB is the smallest in low-latitude regions. The mid-latitude regions exhibit the maximum value of. In contrast, the correlation between TEC and rDCB root mean square (RMS, stability) was greater in low-latitude regions. A strong positive correlation (R≥0.90) on average between TEC and rDCB RMS was also revealed at two additional GNSS stations in low-latitude regions, where the correlation shows clear latitudinal dependency. We found that the correlation between TEC and rDCB stability is still very strong even after replacing a GNSS receiver.

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QUALITY ANALYSIS OF GNSS OBSERVATIONS OF REFERENCE STATIONS NETWORK WITH THE TEQC UTILITY

Vestnik SSUGT (Siberian State University of Geosystems and Technologies) ◽

10.33764/2411-1759-2020-25-3-72-88 ◽

2020 ◽

Vol 25 (3) ◽

pp. 72-88

Author(s):

Vyacheslav E. Tereshchenko ◽

Keyword(s):

Signal To Noise Ratio ◽

Satellite System ◽

Quality Analysis ◽

Signal To Noise ◽

International Gnss Service ◽

Novosibirsk Region ◽

Russian State ◽

Noise Ratio ◽

Gnss Measurements ◽

Global Navigation Satellite

The measurements of Global Navigation Satellite System (GNSS) obtained from different reference stations: Novosibirsk Region reference stations network, Russian state reference stations network ‒ Fundamental Astronomical and Geodetic Networks (FAGN) and stations of International GNSS service (IGS) are checked and analyzed. The relevance of the usage of regional (commercial or industrial) reference stations in state foundation geodetic framework for formation of a unified system of coordinate-time and navigation support is shown. The article describes quality analysis results of the GNSS measurements by the main criteria: number of rejected measurements, ionospheric delay, multipath effect, signal-to-noise ratio, receiver clock slips. The main errors affecting satellite measurements are estimated. The conclusions about the possibility of including the Novosibirsk Region reference stations network into one of the levels of the state foundation geodetic framework are drawn. The comparison of quality of the GNSS measurements showed that according to all criteria of quality the GNSS measurements of the Novosibirsk Region reference stations network are not worse than GNSS measurements of FAGN. According to all criteria the GNSS measurements of the Novosibirsk Region reference stations network approximately corresponds to GNSS measurements of IGS stations, except the signal-to-noise ratio criterion.

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MGR-DCB: A Precise Model for Multi-Constellation GNSS Receiver Differential Code Bias

Journal of Navigation ◽

10.1017/s0373463315000922 ◽

2015 ◽

Vol 69 (4) ◽

pp. 698-708 ◽

Cited By ~ 6

Author(s):

Mohamed Abdelazeem ◽

Rahmi N. Çelik ◽

Ahmed El-Rabbany

Keyword(s):

Total Electron Content ◽

Satellite System ◽

Mean Difference ◽

Electron Content ◽

Vertical Total Electron Content ◽

International Gnss Service ◽

Total Electron ◽

Differential Code Bias ◽

Gnss Receiver ◽

Code Bias

In this study, we develop a Multi-constellation Global Navigation Satellite System (GNSS) Receiver Differential Code Bias (MGR-DCB) model. The model estimates the receiver DCBs for the Global Positioning System (GPS), BeiDou and Galileo signals from the ionosphere-corrected geometry-free linear combinations of the code observations. In order to account for the ionospheric delay, a Regional Ionospheric Model (RIM) over Europe is developed. GPS observations from 60 International GNSS Servoce (IGS) and EUREF reference stations are processed in the Bernese-5·2 Precise Point Positioning (PPP) module to estimate the Vertical Total Electron Content (VTEC). The RIM has spatial and temporal resolutions of 1° × 1° and 15 minutes, respectively. The receiver DCBs for three stations from the International GNSS Service Multi-GNSS Experiment (IGS-MGEX) are estimated for three different days. The estimated DCBs are compared with the MGEX published values. The results show agreement with the MGEX values with mean difference and Root Mean Square Error (RMSE) values less than 1 ns. In addition, the combined GPS, BeiDou and Galileo VTEC values are evaluated and compared with the IGS Global Ionospheric Maps (IGS-GIM) counterparts. The results show agreement with the GIM values with mean difference and RMSE values less than 1 Total Electron Content Unit (TECU).

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IONORING: Real-Time Monitoring of the Total Electron Content over Italy

Remote Sensing ◽

10.3390/rs13163290 ◽

2021 ◽

Vol 13 (16) ◽

pp. 3290

Author(s):

Claudio Cesaroni ◽

Luca Spogli ◽

Giorgiana De Franceschi

Keyword(s):

Real Time ◽

Total Electron Content ◽

Geomagnetic Storms ◽

Single Point ◽

Satellite System ◽

Electron Content ◽

Real Time Monitoring ◽

International Gnss Service ◽

Total Electron ◽

Global Navigation Satellite

IONORING (IONOspheric RING) is a tool capable to provide the real-time monitoring and modeling of the ionospheric Total Electron Content (TEC) over Italy, in the latitudinal and longitudinal ranges of 35°N-48°N and 5°E-20°E, respectively. IONORING exploits the Global Navigation Satellite System (GNSS) data acquired by the RING (Rete Integrata Nazionale GNSS) network, managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The system provides TEC real-time maps with a very fine spatial resolution (0.1° latitude x 0.1° longitude), with a refresh time of 10 min and a typical latency below the minute. The TEC estimated at the ionospheric piercing points from about 40 RING stations, equally distributed over the Italian territory, are interpolated using locally (weighted) regression scatter plot smoothing (LOWESS). The validation is performed by comparing the IONORING TEC maps (in real-time) with independent products: i) the Global Ionospheric Maps (GIM) - final product- provided by the International GNSS Service (IGS), and ii) the European TEC maps from the Royal Observatory of Belgium. The validation results are satisfactory in terms of Root Mean Square Error (RMSE) between 2 and 3 TECu for both comparisons. The potential of IONORING in depicting the TEC daily and seasonal variations is analyzed over 3 years, from May 2017 to April 2020, as well as its capability to account for the effect of the disturbed geospace on the ionosphere at mid-latitudes. The IONORING response to the X9.3 flare event of September 2017 highlights a sudden TEC increase over Italy of about 20%, with a small, expected dependence on the latitude, i.e., on the distance from the subsolar point. Subsequent large regional TEC various were observed in response to related follow-on geomagnetic storms. This storm is also used as a case event to demonstrate the potential of IONORING in improving the accuracy of the GNSS Single Point Positioning. By processing data in kinematic mode and by using the Klobuchar as the model to provide the ionospheric correction, the resulting Horizontal Positioning Error is 4.3 m, lowering to, 3.84 m when GIM maps are used. If IONORING maps are used as the reference ionosphere, the error is as low as 2.5 m. Real-times application and services in which IONORING is currently integrated are also described in the conclusive remarks.

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Comparison of TEC Calculations Based on Trimble, Javad, Leica, and Septentrio GNSS Receiver Data

Remote Sensing ◽

10.3390/rs12193268 ◽

2020 ◽

Vol 12 (19) ◽

pp. 3268

Author(s):

Vladislav Demyanov ◽

Maria Sergeeva ◽

Mark Fedorov ◽

Tatiana Ishina ◽

Victor Jose Gatica-Acevedo ◽

...

Keyword(s):

Carrier Phase ◽

Satellite System ◽

Type Model ◽

Electron Content ◽

Noise Component ◽

Total Electron ◽

Gnss Receiver ◽

Tracking Technique ◽

Gnss Receivers ◽

Global Navigation Satellite

A Global Navigation Satellite System (GNSS) receiver is, to some extent, a “black box” when its data is used for ionospheric studies. Our results based on Javad, Septentrio, Trimble, and Leica GNSS receivers have proven that the accuracy of the slant Total Electron Content (TEC) calculation can differ significantly depending on the GNSS receiver type/model, because TEC measurements depend on the carrier phase tracking technique applied in a receiver. The correlation coefficient between carrier phase noise in L1 and L2 channels is considered as a possible indicator that shows if the L1-aided tracking technique or independent tracking is applied inside a receiver. An empirical model of the TEC noise component was provided to determine the TEC noise value in different types/models of GNSS receivers.

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Potential and limitations of processing smartphone GNSS raw observation data in PPP

10.5194/egusphere-egu21-3345 ◽

2021 ◽

Author(s):

Marcus Franz Glaner ◽

Klaus Gutlederer ◽

Robert Weber

Keyword(s):

Cost Effective ◽

Satellite System ◽

Single Frequency ◽

Reference Network ◽

Observation Data ◽

Data Types ◽

Position Solution ◽

Gnss Measurements ◽

Global Navigation Satellite ◽

Gnss Observations

Since the release of Android 7.0 in 2016, raw GNSS measurements tracked by smartphones operating with Android can be accessed. Before this date, solely the position solution of the smartphone's internal "black box" algorithm could be further processed in various applications. Now the smartphone's GNSS observations can be used directly to estimate the user position with specialized self-developed algorithms and correction data. Since smartphones are equipped with simple, cost-effective GNSS chips and antennas, they provide challenging, low-quality GNSS measurements. Furthermore, most smartphones on the market offer GNSS measurements on just one frequency.&#160;Precise Point Positioning (PPP) is one of the most promising processing techniques for Global Navigation Satellite System (GNSS) data. PPP is characterized by the use of precise satellite products (orbits, clocks, and biases) and the application of sophisticated algorithms to estimate the user's position. In contrast to relative positioning methods, PPP does not rely on nearby reference stations or a regional reference network. Furthermore, the concept of PPP is very flexible, which is another advantage considering the challenging nature of (single frequency) GNSS measurements from smartphones.In this contribution, we present PPP results applying the uncombined model on raw GNSS observations from various smartphone devices. In contrast to the typical use of the ionosphere-free linear combination for PPP, this flexible PPP model applies the raw GNSS observation equations, is suitable for any number of frequencies, and allows the utilization of ionosphere models as an ionospheric constraint. We explore the potential and limitations of using raw GNSS observations from smartphones for PPP to reach a position accuracy at the decimeter level. Therefore, we test different correction data types and algorithms and examine diverse ways to handle the tropospheric and ionospheric delay. The PPP calculations are performed with our self-developed in-house software raPPPid.

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Ionospheric Response over Nepal during the 26 December 2019 Solar Eclipse

Journal of Nepal Physical Society ◽

10.3126/jnphyssoc.v7i1.36970 ◽

2021 ◽

Vol 7 (1) ◽

pp. 25-30

Author(s):

A. Silwal ◽

S. P. Gautam ◽

N. P. Chapagain ◽

M. Karki ◽

P. Poudel ◽

...

Keyword(s):

Solar Eclipse ◽

Satellite System ◽

Electron Content ◽

Total Electron ◽

North West ◽

North East ◽

Apparent Variation ◽

Gnss Measurements ◽

Global Navigation Satellite ◽

Annular Solar Eclipse

On 26th December 2019, during morning hours, an annular solar eclipse having a magnitude of 0.96 with a 118 km wide antumbra occurred and lasted for 3 minutes and 40 seconds at the point of maximum eclipse. The partial eclipse was visible in most of Asia, parts of North/East Africa, and North/West Australia. In the context of Nepal, only the partial eclipse was visible from ~ 8:34 LT (02:51 UT) and ended at ~ 11:40 LT (05:55 UT). It was 2 hours 47 mins and 54 secs long with the maximum visible eclipse time at ~ 10:01 LT (04:16 UT). Our study is based on Global Navigation Satellite System (GNSS) measurements from a widely distributed Global Positioning System (GPS) network over different places of Nepal on the day of the eclipse, a day before, and a day after the eclipse. We investigated the ionospheric behavior through the changes in Total Electron Content (TEC) during the partial eclipse by using the data archived at the five different GPS stations of Nepal. The result reveals that there is significant depletion of TEC, in some cases greater than 20% compared to other normal days. Observing the values of TEC before, during, and after the event, our study showed an apparent variation during the time of the eclipse, which agrees with previous studies on ionospheric responses to the eclipse as well as theoretical assumptions.

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An alternative integer recovery clock method for precise point positioning with ambiguity resolution

Satellite Navigation ◽

10.1186/s43020-020-00028-6 ◽

2020 ◽

Vol 1 (1) ◽

Author(s):

Xingyu Chen

Keyword(s):

Ambiguity Resolution ◽

Precise Point Positioning ◽

Satellite System ◽

International Gnss Service ◽

East Component ◽

The Mean ◽

Point Positioning ◽

Gnss Measurements ◽

Global Navigation Satellite ◽

Globally Distributed

AbstractWhen using Global Navigation Satellite System (GNSS) measurements, Precise Point Positioning with Ambiguity Resolution (PPP-AR) has been a popular substitute for relative positioning in geoscience applications. Compared with the Fractional Cycle Biases (FCB) method, the processing of Integer Recovery Clocks (IRC) products estimate, especially for ambiguity datum fixing, is so complex that its application has been greatly limited. Based on the concept of “carrier range”, we introduce an efficient way to implement the IRC method, termed as the alternative IRC method in this paper. In this method, the fixed ambiguities derived from PPP-AR using the FCB method, and not a fixed-ambiguity datum, are fixed in the IRC products estimate. This greatly reduces the complexity of implementing the IRC method and does not influence the accuracy of positioning. The alternative IRC method outperforms the FCB method by corroborating the consistency of daily positions in nature with international GNSS service weekly solution. To confirm this improvement, global positioning system measurements acquired over a year (2016) from approximately 500 globally distributed stations were processed. The accuracy of IRC products is approximately 20 ps and is highly stable for this year. Moreover, comparing the positioning accuracy of the FCB method to the alternative IRC method, we find that the mean root mean square over the year falls evidently from 2.03 to 1.65 mm at the east component. Therefore, we suggest that the alternative IRC method should be implemented when estimate IRC products.

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Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico

Geosciences ◽

10.3390/geosciences11010016 ◽

2020 ◽

Vol 11 (1) ◽

pp. 16

Author(s):

Christina Oikonomou ◽

Haris Haralambous ◽

Sergey Pulinets ◽

Aakriti Khadka ◽

Shukra R. Paudel ◽

...

Keyword(s):

Chemical Potential ◽

Atmospheric Model ◽

Satellite System ◽

Seismic Events ◽

Electron Content ◽

Total Electron ◽

Atmospheric Disturbances ◽

Global Ionospheric Maps ◽

Global Navigation Satellite ◽

Large Earthquakes

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.

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