Global Ionospheric Model Accuracy Analysis Using Shipborne Kinematic GPS Data in the Arctic Circle

The global ionospheric model built by the International Global Navigation Satellite System (GNSS) Service (IGS) using GNSS reference stations all over the world is currently the most widely used ionospheric product on a global scale. Therefore, analysis and evaluation of this ionospheric product’s accuracy and reliability are essential for the practical use of the product. In contrast to the traditional way of assessing global ionospheric models with ground-based static measurements, our study used shipborne kinematic global positioning system (GPS) measurements collected over 18 days to perform a preliminary analysis and evaluation of the accuracy of the global ionospheric models; our study took place in the Arctic Circle. The data from the International GNSS Service stations near the Arctic Circle were used to verify the ionospheric total electron contents derived from the kinematic data. The results suggested that the global ionospheric model had an approximate regional accuracy of 12 total electron content units (TECu) within the Arctic Circle and deviated from the actual ionospheric total electron content value by about 4 TECu.

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Comparative analysis of global ionospheric models used in GNSS data processing based on selected stations

10.5194/egusphere-egu21-12632 ◽

2021 ◽

Author(s):

Paulina Woźniak ◽

Anna Świątek ◽

Leszek Jaworski

Keyword(s):

Total Electron Content ◽

Satellite System ◽

Ionospheric Delay ◽

Satellite Orbits ◽

Electron Content ◽

Free Electrons ◽

Total Electron ◽

Ionospheric Models ◽

Station Coordinates ◽

The Difference

Among the many error sources affecting GNSS (Global Navigation Satellite System) positioning accuracy, the ionosphere is the cause of those of the greatest value. The ionized gas layer, where also free electrons are present, extends from the upper atmosphere to 1,000 km above the Earth's surface (conventionally). As the GNSS satellite orbits altitude is more than 20,000 km, the wave transmitted from the satellite to the receiver on the Earth&#8217;s ground passes through this layer, but not unscathed. The ionosphere is a dispersive medium for the electromagnetic waves in the microwave band, including UHF (Ultra High Frequency) waves transmitted by GNSS satellites. As a result, the group velocity of the wave decreases, while its phase velocity &#8211; increases.Ionospheric delay compensation methods include among others multi-frequency measurements;&#160; however, when considering measurements on one frequency, the usage of ionospheric models is an option. The key element is the number of free electrons, its inclusion in the course of calculations is possible thanks to the TEC (Total Electron Content) maps. Taking into account the variability of the coefficient in the daily and annual course, as well as depending on the activity of the Sun and its 11-year cycle, it is important to use the current value for a given place and time.For the European Galileo satellite system a dedicated ionospheric model NeQuick-G was developed. As a simple modification of the formula allows it to be applied to other satellite systems, it can be considered in a broader context, regardless of the system and receiver location. In our study the TEC maps published by IGS are used as the comparative data. As a reference, the station located in Warsaw, Poland, is adopted.The subject of this research is the reliability and validity of the model in equatorial region. The analysis is performed for the stations belonging to the IGS (International GNSS Service) network, located in the discussed area. For each hour of the day, independently for each month of 2019, statistic parameters are determined for both models as well as for the difference between them. The results are analysed taking into account the local time of individual stations. The decisive element is the comparison of the station position time series during disturbed and quiet ionospheric conditions (selected based on the K-index), using each of the models (single-frequency observations). The station coordinates are determined from GPS (Global Positioning System) data using the PPP (Precise Point Positioning) method; the position determined for the iono-free combination (dual-frequency observations) is used as a reference.The ionospheric delay is directly proportional to the value of the TEC parameter. The difference between the models, exceeding on average even 20 TECU (Total Electron Content Unit) during some periods, translates into a station coordinate differences. The presented analysis may indicate the need for local improvement of global ionospheric models in the discussed region, which will consequently affect the GNSS positioning quality.

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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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A Comprehensive Analysis of Ionospheric Anomalies before the Mw7·1 Van Earthquake on 23 October 2011

Journal of Navigation ◽

10.1017/s0373463318000826 ◽

2018 ◽

Vol 72 (3) ◽

pp. 702-720 ◽

Cited By ~ 4

Author(s):

Erman Şentürk ◽

Hamdullah Livaoğlu ◽

Murat Selim Çepni

Keyword(s):

Total Electron Content ◽

Activity Index ◽

Satellite System ◽

Electron Content ◽

Vertical Total Electron Content ◽

International Gnss Service ◽

Van Earthquake ◽

Total Electron ◽

Interdisciplinary Approaches ◽

The Van Earthquake

In this study, possible ionospheric precursors of the Mw7·1 Van earthquake are investigated with temporal, spatial and spectral analyses. For this purpose, Global Navigation Satellite System (GNSS) data of 11 International GNSS Service (IGS) stations and 17 Turkish National Permanent Real-Time Kinematic (RTK) Network (TNPGN-Active) stations were utilised. In addition, Global Ionosphere Map (GIM) data produced by the Center for Orbit Determination in Europe (CODE) was used to obtain GIM-vertical Total Electron Content (vTEC) values for the epicentre. The results of the temporal and spectral analysis indicate an increase (2–8 Total Electron Content Units (TECU)) before the Van earthquake occurred on 9 October, 15–16 October and 21–23 October within 15 days, 8–9 days and 1–3 days prior to the earthquake. The Cross-Wavelet Transform (CWT) method was used to examine the presence of correlation between noticeable variations and space-weather. It is deduced from the CWT analysis that the anomalies should originate from either solar effects or the Van earthquake due to coupling between the F10·7 solar activity index and TEC variations on the anomaly days. The results demonstrate that interdisciplinary approaches and various methods including frequency domain could be used to determine the presence of an earthquake-related anomaly in the ionosphere accurately.

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Pecularities of the Total Electron Content and Their Reflections in the Ionospheric Model

PIERS Online ◽

10.2529/piers090902070806 ◽

2010 ◽

Vol 6 (4) ◽

pp. 326-329

Author(s):

Olga A. Maltseva ◽

T. Trinh Quang

Keyword(s):

Total Electron Content ◽

Electron Content ◽

Ionospheric Model ◽

Total Electron

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Methods of detection of changes in the distribution of observed statistics of time derivatives of the total electron content because of cycle slips in navigation satellite’s signals

ITM Web of Conferences ◽

10.1051/itmconf/20193015007 ◽

2019 ◽

Vol 30 ◽

pp. 15007

Author(s):

George Minasyan ◽

Ivan Nesterov ◽

Yaroslav Ilyushin

Keyword(s):

Total Electron Content ◽

Satellite System ◽

Electron Content ◽

Total Electron ◽

Cycle Slips ◽

Phase Data ◽

Total Electronic Content ◽

Global Navigation Satellite ◽

Electronic Content ◽

Derivatives Of

Based on the analysis of the phase data of the global navigation satellite system, distributions of time derivatives of the L1 phase frequency and the total electronic content are obtained. The change in the distributions of observed statistics of time derivatives of the total electron content was analyzed, because there are cycle slips in signals of navigation satellites. According to the analysis of the statistics of the phase of signals, an assumption about the physical and technical reasons for phase failures was made. The correlation between time derivatives of the phase signals and the total electron content has been obtained, despite the apparent dependence of the latter on the phase of the signal. This ratio showed that neither direct nor inverse dependence of the change in the distribution of time derivatives in both of quantities was found.

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Neural network based model for global Total Electron Content forecasting

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2020013 ◽

2020 ◽

Vol 10 ◽

pp. 11 ◽

Cited By ~ 2

Author(s):

Claudio Cesaroni ◽

Luca Spogli ◽

Angela Aragon-Angel ◽

Michele Fiocca ◽

Varuliator Dear ◽

...

Keyword(s):

Neural Network ◽

Total Electron Content ◽

Geomagnetic Storms ◽

Single Point ◽

Global Scale ◽

External Input ◽

Electron Content ◽

International Gnss Service ◽

Total Electron ◽

Grid Points

We introduce a novel empirical model to forecast, 24 h in advance, the Total Electron Content (TEC) at global scale. The technique leverages on the Global Ionospheric Map (GIM), provided by the International GNSS Service (IGS), and applies a nonlinear autoregressive neural network with external input (NARX) to selected GIM grid points for the 24 h single-point TEC forecasting, taking into account the actual and forecasted geomagnetic conditions. To extend the forecasting at a global scale, the technique makes use of the NeQuick2 Model fed by an effective sunspot number R12 (R12eff), estimated by minimizing the root mean square error (RMSE) between NARX output and NeQuick2 applied at the same GIM grid points. The novel approach is able to reproduce the features of the ionosphere especially during disturbed periods. The performance of the forecasting approach is extensively tested under different geospatial conditions, against both TEC maps products by UPC (Universitat Politècnica de Catalunya) and independent TEC data from Jason-3 spacecraft. The testing results are very satisfactory in terms of RMSE, as it has been found to range between 3 and 5 TECu. RMSE depend on the latitude sectors, time of the day, geomagnetic conditions, and provide a statistical estimation of the accuracy of the 24-h forecasting technique even over the oceans. The validation of the forecasting during five geomagnetic storms reveals that the model performance is not deteriorated during disturbed periods. This 24-h empirical approach is currently implemented on the Ionosphere Prediction Service (IPS), a prototype platform to support different classes of GNSS users.

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A New Global Total Electron Content Empirical Model

Remote Sensing ◽

10.3390/rs11060706 ◽

2019 ◽

Vol 11 (6) ◽

pp. 706 ◽

Cited By ~ 6

Author(s):

Jiandi Feng ◽

Baomin Han ◽

Zhenzhen Zhao ◽

Zhengtao Wang

Keyword(s):

Total Electron Content ◽

Empirical Model ◽

Single Point ◽

Empirical Models ◽

Electron Content ◽

International Gnss Service ◽

Prediction Ability ◽

Total Electron ◽

Grid Model ◽

Grid Points

Research on total electron content (TEC) empirical models is one of the important topics in the field of space weather services. Global TEC empirical models based on Global Ionospheric Maps (GIMs) TEC data released by the International GNSS Service (IGS) have developed rapidly in recent years. However, the accuracy of such global empirical models has a crucial restriction arising from the non-uniform accuracy of IGS TEC data in the global scope. Specifically, IGS TEC data accuracy is higher on land and lower over the ocean due to the lack of stations in the latter. Using uneven precision GIMs TEC data as a whole for model fitting is unreasonable. Aiming at the limitation of global ionospheric TEC modelling, this paper proposes a new global ionospheric TEC empirical model named the TECM-GRID model. The model consists of 5183 sections, corresponding to 5183 grid points (longitude 5°, latitude 2.5°) of GIM. Two kinds of single point empirical TEC models, SSM-T1 and SSM-T2, are used for TECM-GRID. According to the locations of grid points, the SSM-T2 model is selected as the sub-model in the Mid-Latitude Summer Night Anomaly (MSNA) region, and SSM-T1 is selected as the sub-model in other regions. The fitting ability of the TECM-GRID model for modelling data was tested in accordance with root mean square (RMS) and relative RMS values. Then, the TECM-GRID model was validated and compared with the NTCM-GL model and Center for Orbit Determination in Europe (CODE) GIMs at time points other than modelling time. Results show that TECM-GRID can effectively describe the Equatorial Ionization Anomaly (EIA) and the MSNA phenomena of the ionosphere, which puts it in good agreement with CODE GIMs and means that it has better prediction ability than the NTCM-GL model.

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Efficiency of updating the ionospheric models using total electron content at mid- and sub-auroral latitudes

GPS Solutions ◽

10.1007/s10291-019-0936-x ◽

2019 ◽

Vol 24 (1) ◽

Cited By ~ 3

Author(s):

Daria S. Kotova ◽

Vladimir B. Ovodenko ◽

Yury V. Yasyukevich ◽

Maxim V. Klimenko ◽

Konstantin G. Ratovsky ◽

...

Keyword(s):

Total Electron Content ◽

Electron Content ◽

Total Electron ◽

Ionospheric Models

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Analysis of a new regional ionospheric assimilated H2PT model for Europe

10.5194/egusphere-egu2020-1524 ◽

2020 ◽

Author(s):

Paulina Woźniak ◽

Anna Świątek ◽

Mariusz Pożoga ◽

Łukasz Tomasik

Keyword(s):

Spatial Resolution ◽

Negative Impact ◽

Satellite System ◽

Electron Content ◽

Maximum Height ◽

Vertical Total Electron Content ◽

Dual Frequency ◽

International Gnss Service ◽

Statistical Parameters ◽

Total Electron

The signal emitted by the GNSS (Global Navigation Satellite System) satellite, on the way to the receiver located on the Earth&#8217;s surface, encounters a heterogeneous layer of ionized gas and free electrons, in which the radio wave is dispersed. As the ionosphere is the source of the highest-value errors among the different factors that affect GNSS positioning accuracy, it is necessary to minimize its negative impact. Various methods are used to compensate for the ionospheric delay, one of which is the usage of models. The intensity of the processes occurring in the ionosphere is closely related to the Sun activity. As a consequence, with respect to a given location on the Earth's surface, the activity of the ionosphere changes throughout the year and day. Therefore, a model dedicated to a specific region is especially important in case of high-precision GNSS applications. The assimilated H2PT model was based on the dual-frequency observations from GNSS stations belonging to EPN (EUREF Permanent Network), as well as on ionosondes participating in the DIAS (European Digital Upper Atmosphere Server) project. The H2PT model covers the Europe area, data with a 15-minutes interval were placed in similar to IONEX (IONosphere Map EXchenge) files in two versions of spatial resolution: 1- and 5-degree. Data provided by the H2PT model are the VTEC (Vertical Total Electron Content) values and the hmF2 (maximum height of the F2 layer) parameters. The subject of this research is the comparison of the H2PT model with NeQuick-G model and IONEX data published by IGS (International GNSS Service) in the context of TEC values as well as determining differences between regional hmF2 data and its commonly used fixed value for the entire globe, amounting to 450 km. In order to perform the analysis, appropriate visualizations were made and statistical parameters determined. Additionally, data from selected periods of positive and negative disturbances were analysed in details based on the developed time series. The relatively high temporal and spatial resolution is undoubtedly an advantage of the H2PT model, because unlike global models, the regional one allows conscientious analysis of the ionosphere characteristics for the area of Europe. Importantly, solutions regarding hmF2 show significant deviations from the fixed value approximated for the whole Earth. Taking into account the parameter appropriate for a given location and time during GNSS data processing may improve the obtained positioning quality.&#160;

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