Study of temporal variation of vertical TEC using NavIC data
01 Nov 2017-
TL;DR: In this article, the authors determined the vertical total electron content (VTEC) and analyzed its diurnal variation for NavIC data, which is used to correct the first order error correction.
Abstract: Determination of Vertical Total Electron Content (VTEC) and analysis of its diurnal variation is presented for NavIC data The radio waves propagating through the ionosphere suffers from a delay depending upon the frequency of radio wave and Total Electron Content (TEC) This delay affects the positional accuracy of the navigation system The proposed study is used to correct this delay called first order error correction
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01 Sep 1965
59 citations
TL;DR: In this article, NavIC's performance in ionospheric studies over the Indian subcontinent region was analyzed using data of one year (2017-2018) at IIT Indore, a location near the northern crest of Equatorial Ionization Anomaly (EIA).
13 citations
Cites background or methods from "Study of temporal variation of vert..."
...…function converts STEC obtained from equation (1) to VTEC and vice versa (Arikan et al. (2003), Jakowski et al. (2011b), Olivier et al. (2015), Bhardwaj et al. (2017)): M(E) = [[ 1 − [Re.cos(E) Re + hI ]2]]−1/2 (9) Here Re is the radius of the Earth (6371 km), hI denotes the altitude of the…...
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...Furthermore (Bhardwaj et al. (2017)) have presented in their study on how to determine VTEC using a dual-frequency method along with a short term analysis on the diurnal variation of NavIC data....
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21 Aug 2020
TL;DR: A brief review of satellite navigation such as working principle, method of position determination, types of reference system used for navigation applications, and techniques of satellite measurements have been discussed.
Abstract: The demand for satellite navigation is increasing exponentially. Even a handheld device (cell phones) can perform positional services due to the advancement of technology. However, the knowledge of its structure and working detail still requires a lot of effort to begin this field because of vast literature available in the public domain. In this paper, a brief review of satellite navigation such as working principle, method of position determination, types of reference system used for navigation applications, and techniques of satellite measurements have been discussed. As the errors in positional services are significant for geodetic applications, the sources of errors in satellite measurements have also been considered separately. This paper will help in understanding the basic principle of satellite navigation and how accurate positioning can be achieved.
11 citations
TL;DR: In this paper, the vertical ionospheric delay of the Indian NavIC system at S1 (2492.028 MHz) and L5 (1176.45 MHz) frequencies has been investigated.
Abstract: To meet the growing requirements of Standard Positioning Services (SPS) and Precision Services (PS), more and more GNSS systems operating at conventional GPS frequencies and higher frequency bands are launched. The Indian NavIC system is one of such systems transmitting navigational signals at S1 (2492.028 MHz) and L5 (1176.45 MHz) frequencies. For GPS at L-band frequencies, comprehensive research work has been conducted to analyze the ionospheric delay to estimate precise user position, although very little research work is available in the public domain at the navigational S-band level. The NavIC program provides opportunities to explore the ionospheric delay effect on S-band navigational signals. The precise position determination demands accurate estimation of the vertical ionospheric delay which is generally obtained using Vertical Electron Content (VTEC) of the ionosphere. The VTEC can be obtained by multiplying a mapping function to the Slant Total Electron Content (STEC). Conventionally a thin shell (also known as a single shell) model is used to map STEC to VTEC, but it introduces error at low elevation angles. This error is significant for the NavIC receivers, located in the northern part of India, as they observe elevation angles below 50◦ for most of the time, and thus there is a need to investigate the suitability of the mapping function model for the NavIC system. As the ionospheric shell height modifies the mapping function and results in a change in VTEC, the height and thickness of the thick shell have been investigated based on the ionospheric data taken from IRI 2016 and were estimated as 300 km and 250 km, respectively. In the present work, the thick shell model has been compared to thin shell model mapping functions to improve the accuracy of VTEC estimation at the low elevation. The reduction in vertical delay using the thick shell mapping function at low elevation indicates its suitability for the locations like Dehradun, India, which lies in the mid-latitude region. Furthermore, the temporal variability of vertical delay at S and L band frequencies has also been investigated to understand the diurnal and seasonal characteristics of ionospheric vertical delay over a period of 12 months to cover all the seasons during the year 2017–18. The vertical delay at the S-band frequency was found to be less than that at the L-band frequency and is almost constant over a month. This finding will be beneficial for single-frequency users and could be used to develop the Grid Ionospheric Vertical Delay (GIVD) map for the NavIC system to enhance positional accuracy.
6 citations
Cites background from "Study of temporal variation of vert..."
...This finding is important for the NavIC receivers, located in the northern part of India [32], as they observe elevation angles below 50◦ for most of the time [33]....
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TL;DR: In this paper , a systematic study of ionospheric scintillation at the low-latitudes, especially around the Equatorial Ionization Anomaly (EIA) and the magnetic equator, is presented.
2 citations
References
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TL;DR: The algorithm designed for this purpose, and implemented in the GPS satellites, requires only eight coefficients sent as part of the satellite message, and contains numerous approximations designed to reduce user computational requirements, yet preserves the essential elements required to obtaingroup delay values along multiple satellite viewing directions.
Abstract: The goal in designing an ionospheric time-delay correctionalgorithm for the single-frequency global positioning system userwas to include the main features of the complex behavior of theionosphere, yet require a minimum of coefficients and usercomputational time, while still yielding an rms correction of at least50 percent. The algorithm designed for this purpose, andimplemented in the GPS satellites, requires only eight coefficientssent as part of the satellite message, contains numerousapproximations designed to reduce user computationalrequirements, yet preserves the essential elements required to obtaingroup delay values along multiple satellite viewing directions.
1,181 citations
"Study of temporal variation of vert..." refers background in this paper
...The conversion of VTEC is done by multiplying obliquity factor, which depends upon elevation angle of the satellite [8], [20]....
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Book•
01 Jan 1965TL;DR: Theory of electromagnetic wave propagation, Theory of electromagnetic Wave Propagation, and Theory of Wave propagation (TWP) as discussed by the authors, is a theory of wave propagation and propagation theory.
Abstract: Theory of electromagnetic wave propagation , Theory of electromagnetic wave propagation , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
315 citations
Book•
01 Jan 1986285 citations
"Study of temporal variation of vert..." refers methods in this paper
...A typical code measurement (Pseudorange) equation is given by [12], [13]:...
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TL;DR: In this paper, the authors analyzed the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007, and found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation.
Abstract: . The dual frequency signals from the GPS satellites recorded at Rajkot (22.29° N, 70.74° E, Geographic, 14.03° N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst=−216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated.
215 citations
"Study of temporal variation of vert..." refers background in this paper
...The conversion of VTEC is done by multiplying obliquity factor, which depends upon elevation angle of the satellite [8], [20]....
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01 Jan 1993
TL;DR: In this article, the effect of the ionosphere on the Global Positioning Systems (GPS) signal for a ground user is estimated based on relaistic modeling of the electron density of the Ionosphere and using a dipole moment approximation for the earth magnetic field.
Abstract: Based on relaistic modeling of the electron density of the ionosphere and using a dipole moment approximation for the earth magnetic field, we are able to estimate the effect of the ionosphere on the Global Positioning Systems (GPS) signal for a ground user. The lowest-order (1/f(exp 2)) effect, which is of the order of .1 - 30 meters of zenith group delay, is subtracted out by forming a linear combination of the dual frequencies of the GPS signal. One is left with second- (1/f(exp 3)) and third-order (1/f(exp 4)) effects which are estimated typically to be approximately 0 - 2 cm, and approximately 0 - 2 mm at zenith respectively, depending on the time of day, time of year, the solar cycle and the relative geometry of the magnetic field and the line of sight. Given the total electron content along a line of sight, we derive an approximation to the second-order term which is accurate to approximately 90% within the magnetic dipole moment model; this approximation can be used to reduce the second-order term to the millimeter level, thus potentially improving precise positioning in space and on the ground. The induced group delay, or phase advance, due to second- and third-order effects are examined for two ground receivers located at equatorial and mid-latitude regions tracking several GPS satellites.
85 citations