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Influence of input parameters for prediction of GPS and IRNSS TEC by using OKRSM at Hyderabad stations during solar fare event

Sivavadivel Kiruthiga, Shunmugam Mythili, Raju Mukesh, Muthuvelan Vijay, Devireddy Kavitha

Acta Geophysica

2022

Vol. 70, no 1

429--443

The solar fare is a threat to the Global Positioning Satellite System (GPS). In this paper, the forecasting capability of Ordinary Kriging-based Response Surface Model (OKRSM) is examined during the X2.2 and X9.3 solar fare that occurred on 6.9.2017. Additionally, its effect on positional accuracy of GPS and IRNSS (Indian Regional Navigation Satellite System) is also evaluated. The GPS and IRNSS VTEC (Vertical Total Electron Content) data are taken from the Hyderabad IGS network station and IRNSS receiver installed at Osmania University, Hyderabad station (17° 24′ 28.07″ N, 78° 31′ 4.26″ E), respectively. The VTEC data of GPS and IRNSS are forecasted from 4th September 2017 to 6th September 2017 by using the previous 6 days of input parameters, GPS and IRNSS TEC data. The parameters like SSN, Kp, Ap, F10.7, ScalarB, Vector B Mag, RMS Mag, RMS Field Vec and Dst were used as inputs for constructing the response surface model. Based on the prediction during the solar fare, it is noted that the model, which was built by using the parameters like ScalarB, Vector B Mag, RMS Field Vec and Dst, gives better prediction results and less range error when compared to other cases used for prediction of TEC. To validate the constructed model, the forecasted TEC of GPS and IRNSS during solar fare is compared with IRI 2016 and IRI PLAS 2017 models. Based on the comparison results, it is found that the developed model showing good agreement with IRNSS data rather than GPS data. The obtained results also show that the IRNSS constellation provides better service in the Indian region when compared to GPS and other models.

Relevance of the relativistic effects in satellite navigation

Kulbiej E.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

2016

nr 47 (119)

85--90

Position determination of Global Navigation Satellite Systems (GNSS) depends on the stability and accuracy of the measured time. However, since satellite vehicles (SVs) travel at velocities significantly larger than the receivers and, more importantly, the electromagnetic impulses propagate through changing gravitational potentials, enormous errors stemming from relativity-based clock offsets would cause a position error of about 11 km to be accumulated after one day. Based on the premise of the constancy of light, two major relativistic effects are described: time dilation and gravitational-frequency shift. Following the individual interests of the author, formulas of both are scrupulously derived from general- and special-relativity theory principles; moreover, in the penultimate section, the equations are used to calculate the author’s own numerical values of the studied parameters for various GNSSs and one Land Navigation Satellite System (LNSS).