Ionospheric Modeling and Forecasting Services of GNSS

The study of ionospheric variability is vital for refining and predicts services of GNSS (Global Navigation Satellite System) applications. The GNSS service provides an explicitly obtainable resource GNSS information, goods and services in support of the earthly reference structure. GNSS is provides an Earth observation, navigation, positioning, timing and other applications that an assistance Society and Science. To investigate the variations in the daily averaged TEC (Total Electron Content) by taking several model components such as solar activity component, geomagnetic activity and periodic components at different latitudes ranging from 10˚N to 26˚N for the year 2018. The presented results would be useful to download, processing and analysis the IGS (International GNSS Service) data. MSSA model can reproduce quite well the observed values of GPS-TEC by utilizing only the first 4 singular modes and constitutes 99% of the total variance. The data is transformed into the singular values which are used for forecasting a noiseless time series. The proposed system results show that higher accuracy is achieved by MSSA (Multivariate Singular Spectrum Analysis) based model. It can also be noted that the training of MSSA is much faster and achieves higher learning accuracy, lowest training time. MSSA is effective even the space weather conditions are active during different solar phase periods.

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

Remote Sensing ◽

10.3390/rs11172062 ◽

2019 ◽

Vol 11 (17) ◽

pp. 2062

Author(s):

Di Wang ◽

Xiaowen Luo ◽

Jinling Wang ◽

Jinyao Gao ◽

Tao Zhang ◽

...

Keyword(s):

Total Electron Content ◽

Satellite System ◽

The Arctic ◽

Electron Content ◽

Ionospheric Model ◽

International Gnss Service ◽

Total Electron ◽

Arctic Circle ◽

Analysis And Evaluation ◽

Ionospheric Models

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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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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Formal estimation of the random component in global maps of total electron content

Advances in Astronomy and Space Physics ◽

10.17721/2227-1481.6.56-60 ◽

2016 ◽

Vol 6 (1) ◽

pp. 56-60 ◽

Cited By ~ 1

Author(s):

V. Choliy

Keyword(s):

Total Electron Content ◽

Singular Spectrum Analysis ◽

Satellite System ◽

Electron Content ◽

Navigation Satellite ◽

Random Component ◽

Optimal Parameters ◽

Total Electron ◽

Global Navigation Satellite

Random component of the total electron content (TEC) maps, produced by global navigation satellite system processing centres, was analysed. Helmert transform (HT) and two-dimension singular spectrum analysis (2dSSA) were used. Optimal parameters (in the sense calculation speed versus quality) of the 2dSSA windows were determined along with precision estimations.

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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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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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Characterization of multi-scale ionospheric irregularities using ground-based and space-based GNSS observations

Satellite Navigation ◽

10.1186/s43020-021-00047-x ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

YuXiang Peng ◽

Wayne A Scales ◽

Michael D Hartinger ◽

Zhonghua Xu ◽

Shane Coyle

Keyword(s):

Formation Flying ◽

Satellite System ◽

Ionospheric Irregularities ◽

Mission Design ◽

Electron Content ◽

Total Electron ◽

Spatial And Temporal Scales ◽

Multi Scale ◽

Global Navigation Satellite ◽

Gnss Observations

AbstractIonospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). However, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregularities for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observation technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.

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Investigation of GIM-TEC disturbances before M ≥ 6.0 inland earthquakes during 2003–2017

Scientific Reports ◽

10.1038/s41598-020-74995-w ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Fuying Zhu ◽

Yingchun Jiang

Keyword(s):

Rapid Development ◽

Science Research ◽

Satellite System ◽

Statistical Investigation ◽

Electron Content ◽

Total Electron ◽

Spatial And Temporal Distributions ◽

Before And After ◽

Global Ionosphere Map ◽

Global Navigation Satellite

Abstract With the rapid development of the Global Navigation Satellite System (GNSS) and its wide applications to atmospheric science research, the global ionosphere map (GIM) total electron content (TEC) data are extensively used as a potential tool to detect ionospheric disturbances related to seismic activity and they are frequently used to statistically study the relation between the ionosphere and earthquakes (EQs). Indeed, due to the distribution of ground based GPS receivers is very sparse or absent in large areas of ocean, the GIM-TEC data over oceans are results of interpolation between stations and extrapolation in both space and time, and therefore, they are not suitable for studying the marine EQs. In this paper, based on the GIM-TEC data, a statistical investigation of ionospheric TEC variations of 15 days before and after the 276 M ≥ 6.0 inland EQs is undertaken. After eliminating the interference of geomagnetic activities, the spatial and temporal distributions of the ionospheric TEC disturbances before and after the EQs are investigated and compared. There are no particularly distinct features in the time distribution of the ionospheric TEC disturbances before the inland EQs. However, there are some differences in the spatial distribution, and the biggest difference is precisely in the epicenter area. On the other hand, the occurrence rates of ionospheric TEC disturbances within 5 days before the EQs are overall higher than those after EQs, in addition both of them slightly increase with the earthquake magnitude. These results suggest that the anomalous variations of the GIM-TEC before the EQs might be related to the seismic activities.

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Estimation and Analysis of GNSS Differential Code Biases (DCBs) Using a Multi-Spacing Software Receiver

Sensors ◽

10.3390/s21020443 ◽

2021 ◽

Vol 21 (2) ◽

pp. 443

Author(s):

Ye Wang ◽

Lin Zhao ◽

Yang Gao

Keyword(s):

Primary Source ◽

Intermediate Frequency ◽

Global Navigation Satellite Systems ◽

Electron Content ◽

Software Receiver ◽

International Gnss Service ◽

Total Electron ◽

Satellite Systems ◽

Differential Code Biases ◽

Gnss Observations

In the use of global navigation satellite systems (GNSS) to monitor ionosphere variations by estimating total electron content (TEC), differential code biases (DCBs) in GNSS measurements are a primary source of errors. Satellite DCBs are currently estimated and broadcast to users by International GNSS Service (IGS) using a network of GNSS hardware receivers which are inside structure fixed. We propose an approach for satellite DCB estimation using a multi-spacing GNSS software receiver to analyze the influence of the correlator spacing on satellite DCB estimates and estimate satellite DCBs based on different correlator spacing observations from the software receiver. This software receiver-based approach is called multi-spacing DCB (MSDCB) estimation. In the software receiver approach, GNSS observations with different correlator spacings from intermediate frequency datasets can be generated. Since each correlator spacing allows the software receiver to output observations like a local GNSS receiver station, GNSS observations from different correlator spacings constitute a network of GNSS receivers, which makes it possible to use a single software receiver to estimate satellite DCBs. By comparing the MSDCBs to the IGS DCB products, the results show that the proposed correlator spacing flexible software receiver is able to predict satellite DCBs with increased flexibility and cost-effectiveness than the current hardware receiver-based DCB estimation approach.

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