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

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

<p>Among the many error sources affecting GNSS <em>(Global Navigation Satellite System)</em> 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’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 <em>(Ultra High Frequency)</em> waves transmitted by GNSS satellites. As a result, the group velocity of the wave decreases, while its phase velocity – increases.</p><p>Ionospheric delay compensation methods include among others multi-frequency measurements;  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 <em>(Total Electron Content)</em> 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.</p><p>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.</p><p>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 <em>(International GNSS Service)</em> 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 <em>(Global Positioning System)</em> data using the PPP <em>(Precise Point Positioning)</em> method; the position determined for the iono-free combination (dual-frequency observations) is used as a reference.</p><p>The ionospheric delay is directly proportional to the value of the TEC parameter. The difference between the models, exceeding on average even 20 TECU <em>(Total Electron Content Unit)</em> 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.</p>

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

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.

scholarly journals 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

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.

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

GPS Solutions ◽  
2019 ◽  
Vol 24 (1) ◽  
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

scholarly journals A ROTI-Aided Equatorial Plasma Bubbles Detection Method

2021 ◽  
Vol 13 (21) ◽  
pp. 4356
Author(s):  
Long Tang ◽  
Osei-Poku Louis ◽  
Wu Chen ◽  
Mingli Chen
Keyword(s):  
Hong Kong ◽  
Total Electron Content ◽  
Detection Method ◽  
Temporal Distribution ◽  
Satellite System ◽  
Previous Method ◽  
Electron Content ◽  
Total Electron ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles

In this study, we present a Rate of Total Electron Content Index (ROTI)-aided equatorial plasma bubbles (EPBs) detection method based on a Global Navigation Satellite System (GNSS) ionospheric Total Electron Content (TEC). This technique seeks the EPBs occurrence time according to the ROTI values and then extracts the detrended ionospheric TEC series, which include EPBs signals using a low-order, partial polynomial fitting strategy. The EPBs over the Hong Kong area during the year of 2014 were detected using this technique. The results show that the temporal distribution and occurrence of EPBs over the Hong Kong area are consistent with that of previous reports, and most of the TEC depletion error is smaller than 1.5 TECU (average is 0.63 TECU), suggesting that the detection method is feasible and highly accurate. Furthermore, this technique can extract the TEC depletion series more effectively, especially for those with a long duration, compared to previous method.

scholarly journals Single point positioning with vertical total electron content estimation based on single-epoch data

2021 ◽  
Vol 10 (1) ◽  
pp. 1-12
Author(s):  
Artur Fischer ◽  
Sławomir Cellmer ◽  
Krzysztof Nowel
Keyword(s):  
Total Electron Content ◽  
Single Point ◽  
Error Reduction ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Single Point Positioning ◽  
External Data ◽  
Point Positioning

Abstract. This paper proposes a new mathematical method of ionospheric delay estimation in single point positioning (SPP) using a single-frequency receiver. The proposed approach focuses on the Δ vertical total electron content (VTEC) component estimation (MSPPwithdVTEC) with the assumption of an initial and constant value equal to 5 TECU in any observed epoch. The principal purpose of the study is to examine the reliability of this approach to become independent from the external data in the ionospheric correction calculation process. To verify the MSPPwithdVTEC, the SPP with the Klobuchar algorithm was employed as a reference model, utilizing the coefficients from the navigation message. Moreover, to specify the level of precision of the MSPPwithdVTEC, the SPP with the International Global Navigation Satellite Systems (GNSS) Service (IGS) TEC map was adopted for comparison as the high-quality product in the ionospheric delay determination. To perform the computational tests, real code data were involved from three different localizations in Scandinavia using two parallel days. The criterion was the ionospheric changes depending on geodetic latitude. Referring to the Klobuchar model, the MSPPwithdVTEC obtained a significant improvement of 15 %–25 % in the final SPP solutions. For the SPP approach employing the IGS TEC map and for the MSPPwithdVTEC, the difference in error reduction was not significant, and it did not exceed 1.0 % for the IGS TEC map. Therefore, the MSPPwithdVTEC can be assessed as an accurate SPP method based on error reduction value, close to the SPP approach with the IGS TEC map. The main advantage of the proposed approach is that it does not need external data.

Performance Evaluation of USTEC Product for Single-Frequency Precise Point Positioning

GEOMATICA ◽  
2013 ◽  
Vol 67 (4) ◽  
pp. 253-257 ◽  
Author(s):  
Mahmoud Abd El-Rahman ◽  
Ahmed El-Rabbany
Keyword(s):  
Total Electron Content ◽  
Precise Point Positioning ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Gps Receivers ◽  
Mitigation Techniques ◽  
Point Positioning

Geodetic-grade dual-frequency GPS receivers are typically used for precise point positioning (PPP). Unfortunately, these receiver systems are expensive and may not provide a cost-effective solution in many instances. The use of low-cost single-frequency GPS receivers, on the other hand, are limited by the effect of ionospheric delay. A number of mitigation techniques have been proposed to account for the effect of ionospheric delay for single-frequency GPS users. Unfortunately, however, those mitigation techniques are not suitable for PPP. More recently, the U.S. Total Electron Content (USTEC) product has been developed by the National Oceanic and Atmospheric Administration (NOAA), which describes the ionospheric total electron content in high resolution over most of North America. This paper investigates the performance of USTEC and studies its effect on single-frequency PPP solution. A performance comparison with two widely-used ionospheric mitigation models is also presented.

scholarly journals Deep learning of total electron content

2021 ◽  
Vol 3 (7) ◽  
Author(s):  
Omid Memarian Sorkhabi
Keyword(s):  
Deep Learning ◽  
Total Electron Content ◽  
Single Layer ◽  
Activation Function ◽  
Satellite System ◽  
Single Frequency ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Global Navigation Satellite

AbstractOne of the most notable errors in the global navigation satellite system (GNSS) is the ionospheric delay due to the total electron content (TEC). TEC is the number of electrons in the ionosphere in the signal path from the satellite to the receiver, which fluctuates with time and location. This error is one of the major problems in single-frequency (SF) GPS receivers. One way to eliminate this error is to use dual-frequency. Users of SF receivers should either use estimation models or local models to reduce this error. In this study, deep learning of artificial neural networks (ANN) was used to estimate TEC for SF users. For this purpose, the ionosphere as a single-layer model (assuming that all free electrons in the ionosphere are in this thin layer) is locally modeled by the code observation method. Linear combination has been used by selecting 24 permanent GNSS stations in the northwest of Iran. TEC was modeled independently of the geometry between the satellite and the receiver, called L4. This modeling was used to train the error ANN with two 5-day periods of high and low solar and geomagnetic activity range with a hyperbolic tangential sigmoid activation function. The results show that the proposed method is capable of eliminating ionosphere error with an average accuracy of 90%. The international reference ionosphere 2016 (IRI2016) is used for the verification, which has a 96% significance correlation with estimated TEC.

scholarly journals Double-thin-shell approach to deriving total electron content from GNSS signals and implications for ionospheric dynamics near the magnetic equator

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takashi Maruyama ◽  
Kornyanat Hozumi ◽  
Guanyi Ma ◽  
Pornchai Supnithi ◽  
Napat Tongkasem ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Thin Shell ◽  
Spherical Surface ◽  
Satellite System ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Functional Fitting ◽  
A New Technique ◽  
Global Navigation Satellite

AbstractA new technique was developed to estimate the ionospheric total electron content (TEC) from Global Navigation Satellite System (GNSS) satellite signals. The vertically distributed electron density was parameterized by two thin-shell layers (double-shell approach). The spatiotemporal variation of TEC (strictly speaking, partial electron content) associated with each shell was approximated by the functional fitting of spherical surface harmonics. The major improvements over the conventional single-shell approach were as follows: (1) the precise estimation of TEC was achieved; (2) the estimated TEC was less dependent on the choice of shell heights; and (3) the equatorial anomaly was captured more correctly. Furthermore, higher and lower shells exhibited a different pattern of local time vs latitude variation, providing information on the ionosphere–thermosphere dynamics.

scholarly journals Some statistics of Ionospheric total electron content variations at mid-latitude zones of Mongolia

2021 ◽  
pp. 1-8
Author(s):  
Baatarkhuu Dagva ◽  
Amarjargal Sharav ◽  
Lkhagvajav Chultemiin
Keyword(s):  
Total Electron Content ◽  
Satellite System ◽  
Electron Content ◽  
Sudden Increase ◽  
Dual Frequency ◽  
Total Electron ◽  
Rotation Of The Earth ◽  
Global Navigation Satellite ◽  
Continuous Gps ◽  
Geomagnetic Activities

This work is focused on the correlation of ionosphere total electron content (TEC) with solar and geomagnetic activities of the space weather at mid-latitude zone.  In our analysis, we investigate the TEC time series obtained from dual-frequency GNSS (Global Navigation Satellite System) observations at three continuous GPS/GNSS stations HOVD (48.00N, 91.66E), CHOB (48.08N, 114.53E) and DALN (43.56N, 104.42) for 2013. The statistical analyses are performed on 15 minute averaged yearly TEC values, which reveal the semi-annual anomaly and high correlation with the activities of the Sun and the rotation of the Earth. Phase overlapping seasonal variations of TEC and Sunspot, and Solar flux (10.7) indices, and Earth rotations (LOD) and Atmospheric angular moment (AAM) are observed in our data analyses. Sudden ionospheric storm changes in TEC with geomagnetic storm induced by the extreme solar flare and 2013 events were investigated. The result shows that GPS derived TEC behaves as an indicator of these events showing sudden increase in TEC during the event.

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