Evaluation of the IGS–Global Ionospheric Mapping model over Egypt

Ionospheric Correction ◽

Total Electron ◽

The North ◽

Using Data

Abstract. Global ionosphere maps (GIM) are generated on a daily basis at CODE using data from about 400 GPS/GLONASS sites of the IGS and other institutions. The vertical total electron content (VTEC) is modeled in a solar-geomagnetic reference frame using a Spherical Harmonics Expansion “SHE” up to degree and order 15. To cover the holes of the first GIM computation stage existing in the North Africa and over the Oceans resulting a shortage of GNSS station in North Africa, an optimum spatial-temporal interpolation technique was developed to cover these holes (Krankowski and Hernandez-Pajares, 2016). The current paper evaluates the ionospheric correction by Global Ionospheric Maps, GIM, provided in (IONEX) files produced by International GNSS Services “IGS”. The evaluation is performed based on investigating the effect of a given GIM ionospheric correction on kinematic relative positioning solutions. The evaluation was done using several baselines of different lengths in Egypt. The results show that there is no significant effect of the provided GIM values on the solution of kinematic processing. The results confirm that although there is a lack of International GNSS Service (IGS stations) over North Africa, GIMs have no effect in mitigating ionospheric error. A new value for the ionosphere correction VTEC values was obtained by a regional, developed algorithm based on zero-differenced phase ionospheric delay (ZDPID) (Tawfeek et al., 2018). These new values of VTEC were fed into GIMs for the specified stations data. A useful result was obtained for correcting the ionospheric error over kinematic solution of many baseline lengths up to 300 km which demonstrates validity of the proposed evaluation method.

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 ◽

Dual Frequency ◽

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;

ANALYSES OF TOTAL ELECTRON CONTENT VARIATIONS OVER NORTHERN AND SOUTHERN NIGERIA

JOURNAL OF RESEARCH AND REVIEW IN SCIENCE ◽

10.36108/jrrslasu/7102/40(0140) ◽

2017 ◽

Vol 4 (1) ◽

Author(s):

Aghogho Ogwala

Keyword(s):

Total Electron Content ◽

Seasonal Variations ◽

Electron Content ◽

Dual Frequency ◽

The South ◽

Total Electron ◽

The North ◽

December Solstice ◽

Latitudinal Difference

Total electron content (TEC) is a parameter of the ionosphere that produces great effect on radio signals. We present the diurnal and seasonal variations of vertical total electron content (vTEC) during the ascending phase of solar cycle 24. A moderate solar activity year (2011) with sunspot number, Rz = 55.7 is used in this study. Total electron content (TEC) deduced from the dual frequency GPS measurements obtained at two ground stations namely: ABUZ (Zaria) with longitude 7.39oE in the north and UNEC (Enugu) with longitude 7.30oE in the south are considered. Both stations are located within the same longitude and has a latitudinal difference of 4.74o in the Nigerian equatorial ionosphere (NEI). Comparison of diurnal and seasonal variations of TEC is carried out for both stations. The diurnal variation of TEC shows a steep increase starting from sunrise, reaching daytime maximum between 13 – 15 LT at UNEC and 14 – 16 LT at ABUZ, then falls to a minimum at sunset. Dawn depression occurred at the same local time of 04 LT at both stations. On a seasonal scale, Pre- and post-midnight values were highest during the Equinoxes, followed by December solstice and least in June Solstice season at ABUZ. Pre- and post-midnight values were also higher during the Equinoxes than the Solstice season at UNEC, although they are about the same range. Also, TEC values are observed to be slightly higher for all hours and seasons at Enugu in the south than Zaria in the north except during March equinox at Zaria where TEC values were higher during the daytime. This implies that there could be little variations in TEC even within the same latitudinal zone.

Redes neurais artificiais aplicadas na previsão do VTEC no Brasil

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702013000200005 ◽

2013 ◽

Vol 19 (2) ◽

pp. 227-246 ◽

Cited By ~ 1

Author(s):

Wagner Carrupt Machado ◽

Edvaldo Simões da Fonseca Junior

Keyword(s):

Total Electron Content ◽

Electron Content ◽

Total Electron ◽

De Se ◽

Pierce Point ◽

Global Ionospheric Maps

Uma forma de se prever o conteúdo total de elétrons na direção vertical (VTEC - Vertical Total Electron Content) usando a arquitetura de redes neurais artificiais (RNA) denominada de perceptrons de múltiplas camadas (MLP - MultipLayer Percetrons) é apresentada e avaliada nesta pesquisa. As entradas do modelo foram definidas como sendo a posição dos pontos ionosféricos (IPP - Ionospheric Pierce Point) e o tempo universal (TU), enquanto que a saída é o VTEC. As variações sazonais e de períodos mais longos são levadas em conta através da atualização do treinamento diariamente. Testes foram conduzidos sobre uma área que abrange o Brasil e sua vizinhança considerando períodos de alta e baixa atividade solar. As RNA foram treinadas utilizando informações dos mapas globais da ionosfera (GIM - Global Ionospheric Maps) produzidos pelo serviço internacional do GNSS (IGS - International GNSS Service) das 72 horas anteriores à época de início da previsão. As RNA treinadas foram utilizadas para prever o VTEC por 72 horas (VTEC RNA). Os VTEC RNA foram comparados com os VTEC contidos nos GIM (VTEC GIM). A raiz do erro médio quadrático (RMS) da diferença entre o VTEC GIM e o VTEC RNA variou de 1,4 a 10,7 unidades de TEC (TECU). O erro relativo mostra que a RNA proposta foi capaz de prever o VTEC com 70 a 85% de acerto.

Performance Evaluation of VTEC GIMs for Regional Applications during Different Solar Activity Periods, Using RING TEC Values

Remote Sensing ◽

10.3390/rs13081470 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1470

Author(s):

Vincenza Tornatore ◽

Claudio Cesaroni ◽

Michael Pezzopane ◽

Mohamad Mahdi Alizadeh ◽

Harald Schuh

Keyword(s):

Solar Activity ◽

Time Windows ◽

Regional Level ◽

Electron Content ◽

Dual Frequency ◽

Calibration Technique ◽

Total Electron ◽

Gps Receivers ◽

The North

This paper presents a comparison of the vertical total electron content (vTEC) estimated over Italy using two different approaches: the GPS Global Ionosphere Maps (GIMs) and the so-called “calibration technique” developed by Ciraolo in 2007. The study has been carried out at a regional level by considering three Italian dual-frequency stations of the GPS permanent network “Rete Integrata Nazionale GPS (RING)”. The GPS receivers are permanently installed at Madesimo (geographical coordinates: 46.5 N, 9.4 E), Rome (geographical coordinates: 41.8 N, 12.5 E) and Resuttano (geographical coordinates: 37.7 N, 14.1 E), respectively in the north, center and south of Italy. Time windows selected for the analysis include periods of both low (July 2008 to June 2009) and high (September 2013 to August 2014) solar activity. The two datasets have also been studied considering both quiet and disturbed geomagnetic activity conditions. Moreover, the effects of an extreme geomagnetic storm have been investigated in March 2015 when the well-known St. Patrick storm occurred. Overall, GIM estimated values are always higher than those calibrated by the Ciraolo procedure for all the considered datasets. The differences between the two methods increase as the latitude decreases, and they increase as the solar activity intensifies. The outcomes of this study shall be helpful when applying GlMs at a regional level.

Ionosphere VTEC modeling with the raw-observation-based PPP model：an advantage demonstration in the multi-frequency and multi-GNSS context

10.5194/egusphere-egu2020-12914 ◽

2020 ◽

Author(s):

Teng Liu ◽

Baocheng Zhang ◽

Yunbin Yuan ◽

Xiao Zhang

Keyword(s):

Rapid Development ◽

Global Navigation Satellite Systems ◽

Electron Content ◽

Dual Frequency ◽

Total Electron ◽

Satellite Systems ◽

Triple Frequency ◽

Global Navigation Satellite

The ionospheric delay accounts for one of the major errors that the Global Navigation Satellite Systems (GNSS) suffer from. Hence, the ionosphere Vertical Total Electron Content (VTEC) map has been an important atmospheric product within the International GNSS Service (IGS) since its early establishment. In this contribution, an enhanced method has been proposed for the modeling of the ionosphere VTECs. Firstly, to cope with the rapid development of the newly-established Galileo and BeiDou constellations in recent years, we extend the current dual-system (GPS/GLONASS) solution to a quad-system (GPS/GLONASS/Galileo/BeiDou) solution. More importantly, instead of using dual-frequency observations based on the Carrier-to-Code Leveling (CCL) method, all available triple-frequency signals are utilized with a general raw-observation-based multi-frequency Precise Point Positioning (PPP) model, which can process dual-, triple- or even arbitrary-frequency observations compatibly and flexibly. Benefiting from this, quad-system slant ionospheric delays can be retrieved based on multi-frequency observations in a more flexible, accurate and reliable way. The PPP model has been applied in both post-processing global and real-time regional VTEC modeling. Results indicate that with the improved slant ionospheric delays, the corresponding VTEC models are also improved, comparing with the traditional CCL method.

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 ◽

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).

Towards Cooperative Global Mapping of the Ionosphere: Fusion Feasibility for IGS and IRI with Global Climate VTEC Maps

Remote Sensing ◽

10.3390/rs12213531 ◽

2020 ◽

Vol 12 (21) ◽

pp. 3531

Author(s):

Adam Froń ◽

Ivan Galkin ◽

Andrzej Krankowski ◽

Dieter Bilitza ◽

Manuel Hernández-Pajares ◽

...

Keyword(s):

Global Climate ◽

Slab Thickness ◽

Electron Content ◽

Total Electron ◽

Global Mapping ◽

History Of ◽

Ionospheric Plasma Density ◽

Climate Maps

Recommendations of the International Reference Ionosphere (IRI) Workshop 2017 in Taoyuan City, Taiwan and International GNSS Service (IGS) Workshop 2018 in Wuhan, China included establishment of an ionosphere mapping service that would fuse measurements from two independent sensor networks: IGS permanent GNSS receivers providing the vertical total electron content (VTEC) measurements and ionosondes of the Global Ionosphere Radio Observatory (GIRO) that compute the bottomside vertical profiles of the ionospheric plasma density. Using available GAMBIT software at GIRO, we introduced new VTEC products to its data roster: previously unavailable global average (climate) maps of VTEC and slab thickness based on climatological capabilities of IRI. Incorporation of the VTEC and τ maps into the GAMBIT Explorer environment provided data analysts with nearly 10-year history of the reference average VTEC records and opened access to the GAMBIT toolkit for evaluation and validation of the τ computations. This result is the first step towards establishing an infrastructure and the data workflow to provide GAMBIT users with the low latency and consistent quality and usability of the ionospheric weather-climate specifications. Combination of IGS-provided VTEC and GIRO-provided peak density of F2 layer NmF2 allows ground-based evaluation of the equivalent slab thickness τ, a derived property of the near-Earth plasma that characterizes the skewness of its vertical profile up to the GNSS spacecraft altitudes.

The cooperative IGS RT-GIMs: a reliable estimation of the global ionospheric electron content distribution in real time

Earth System Science Data ◽

10.5194/essd-13-4567-2021 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4567-4582

Author(s):

Qi Liu ◽

Manuel Hernández-Pajares ◽

Heng Yang ◽

Enric Monte-Moreno ◽

David Roma-Dollase ◽

...

Keyword(s):

Real Time ◽

Geomagnetic Storms ◽

Quality Data ◽

Electron Content ◽

Strong Response ◽

Total Electron ◽

The Real ◽

Testing Period

Abstract. The Real-Time Working Group (RTWG) of the International GNSS Service (IGS) is dedicated to providing high-quality data and high-accuracy products for Global Navigation Satellite System (GNSS) positioning, navigation, timing and Earth observations. As one part of real-time products, the IGS combined Real-Time Global Ionosphere Map (RT-GIM) has been generated by the real-time weighting of the RT-GIMs from IGS real-time ionosphere centers including the Chinese Academy of Sciences (CAS), Centre National d'Etudes Spatiales (CNES), Universitat Politècnica de Catalunya (UPC) and Wuhan University (WHU). The performance of global vertical total electron content (VTEC) representation in all of the RT-GIMs has been assessed by VTEC from Jason-3 altimeter for 3 months over oceans and dSTEC-GPS technique with 2 d observations over continental regions. According to the Jason-3 VTEC and dSTEC-GPS assessment, the real-time weighting technique is sensitive to the accuracy of RT-GIMs. Compared with the performance of post-processed rapid global ionosphere maps (GIMs) and IGS combined final GIM (igsg) during the testing period, the accuracy of UPC RT-GIM (after the improvement of the interpolation technique) and IGS combined RT-GIM (IRTG) is equivalent to the rapid GIMs and reaches around 2.7 and 3.0 TECU (TEC unit, 1016 el m−2) over oceans and continental regions, respectively. The accuracy of CAS RT-GIM and CNES RT-GIM is slightly worse than the rapid GIMs, while WHU RT-GIM requires a further upgrade to obtain similar performance. In addition, a strong response to the recent geomagnetic storms has been found in the global electron content (GEC) of IGS RT-GIMs (especially UPC RT-GIM and IGS combined RT-GIM). The IGS RT-GIMs turn out to be reliable sources of real-time global VTEC information and have great potential for real-time applications including range error correction for transionospheric radio signals, the monitoring of space weather, and detection of natural hazards on a global scale. All the IGS combined RT-GIMs generated and analyzed during the testing period are available at https://doi.org/10.5281/zenodo.5042622 (Liu et al., 2021b).

Characterization of GPS-TEC in a low-latitude region over Thailand during 2010-2012

Annals of Geophysics ◽

10.4401/ag-6717 ◽

2015 ◽

Vol 58 (5) ◽

Author(s):

V. Rajesh Chowdhary ◽

Nitin K. Tripathi ◽

Sanit Arunpold ◽

Durairaju Kumaran Raju

Keyword(s):

Ultra Violet ◽

Electron Content ◽

Dual Frequency ◽

Chiang Mai ◽

Total Electron ◽

Gps Tec ◽

First Results ◽

June July

This paper presents the first results of vertical total electron content (VTEC) data from (1) a dual-frequency GPS receiver installed at the Chiang Mai University in Chiang Mai (CHGM, 18.480 N, 98.570 E) as part of SCINDA (Scintillation Network and Decision Aid) and (2) the International GNSS Service (IGS) station Pathum Wan (CUSV, 13.735 N, 100.533 E) with magnetic latitude of 8.69°N and 3.92°N respectively in Thailand, from August 2010 to July 2012. In the equatorial ionization anomaly (EIA) region, these two stations are separated at a distance of 668 km. Observed GPS-TEC values were found to be the highest between 1500 and 1900 Local Time (LT) throughout the study period at both the stations. The GPS-TEC data from both the stations was plotted diurnal, monthly and seasonal analyses were performed. The equinox (March, April, September, and October) and solstice (January, February, June, July, and December) periods had maximum and minimum diurnal peak variations, respectively, of the GPS-TEC. High TEC values are attributed to extreme solar ultra-violet ionization coupled with upward vertical E×B drift. A comparison of the GPS-TEC data from both the stations for the study period shows that the CHGM station recorded higher values of TEC than the CUSV station because of the formation of an ionization crest over the CHGM station. The GPS-TEC values also exhibited an increasing trend-because of the approach of solar cycle 24. For data validation, the diurnal, monthly, and seasonal variations in the measured TEC were compared with the TEC modelled in the International Reference Ionosphere (IRI) models (IRI-2007 and the recently released IRI-2012 model). The IRI-2007 shows good agreement with the data from 2010 to 2011 from both stations and IRI-2012 agrees well with the data from 2012 onwards compared to IRI-2007.

SCINDA-GPS derived TEC depletions and amplitude scintillations over Kisumu, Kenya during selected quiet and storm days of 2013 and 2014

International Journal of Advanced Astronomy ◽

10.14419/ijaa.v8i1.30232 ◽

2020 ◽

Vol 8 (1) ◽

pp. 1

Author(s):

Uluma Edward ◽

Ndinya Boniface ◽

Omondi George

Keyword(s):

Total Electron Content ◽

Equatorial Region ◽

Activity Period ◽

High Solar Activity ◽

Electron Content ◽

Gps Receiver ◽

Total Electron ◽

Solar Intensity ◽

Using Data

Total Electron Content (TEC) depletion and amplitude scintillation (S4) can be derived from, SCINDA-GPS receivers situated in various parts of the equatorial region. In this paper we present results of characterization of TEC depletions and amplitude scintillations over Kisumu, Kenya (Geomagnetic coordinates: 9.64o S, 108.59o E; Geographic coordinates: 0.02o S, 34.6o E) for both selected geomagnetically quiet and geomagnetically disturbed conditions between 1st January 2013 and 31st December 2014 using data derived from the Kisumu NovAtel GSV4004B SCINDA-GPS receiver situated at Maseno University. TEC depletions and amplitude scintillations affect Global Positioning System (GPS) signals in the ionosphere as they propagate from the satellite to the receiver. This study aims to investigate day to day variability of TEC depletions and amplitude scintillations over Kisumu, Kenya during both geomagnetically quiet and geomagnetically disturbed days of 2013 and 2014 which was a high solar activity period for Solar Cycle 24. Seasonal variability of TEC depletions and S4 index is also presented. The Receiver Independent Exchange (RINEX) data for the years 2013 and 2014 was retrieved from the Kisumu SCINDA-GPS receiver, processed to obtain Vertical Total Electron Content (VTEC), S4 and Universal Time (UT) and fed into MATLAB to generate VTEC and S4 plots against UT for each selected quiet and storm day within the 2013 and 2014 period. The obtained results showed a diurnal variation of TEC where TEC was minimum at pre-sunrise, maximum during daytime and minimum during nighttime. The minimum TEC during pre-sunrise and nighttime was attributed to reduced solar intensity while maximum TEC during daytime is attributed to increased solar intensity. Most of the selected quiet and storm days of the years 2013 and 2014 showed TEC depletions and TEC enhancements corresponding with enhanced amplitude scintillations between 1800UT and 20:00UT. This might be attributed to the rapid rise of the F-layer and the increase in the vertical E x B plasma drift due to the Pre-reversal Enhancement (PRE) of the eastward electric field. Post-midnight TEC depletions and amplitude scintillations were observed for some days and this was attributed to the effect of zonal winds which brought post-midnight enhancement of the E x B drift. The percentage occurrence of amplitude scintillations for the selected quiet and storm days exhibited a seasonal dependence with equinoctial months having higher occurrences than the solstitial months. The higher average S4 index during equinoctial months might be attributed to increased solar intensity resulting from the close alignment of the solar terminator and the geomagnetic meridian.