Abstract
The ionosphere is a dispersive medium of charged particles between the satellite and the user on Earth. These dispersive ionized media play a vital role in the various applications of GPS (Global Positioning Systems) because the ionosphere directly influences transionospheric radio waves propagating from the satellite to the receiver. Solar flares affect the ionization state of the ionosphere with their high intensity. Sometimes the intensity is so severe that it accelerates the rate of ionization, resulting in ionospheric storms; during the ionospheric storms the concentration of charged particles varies. Among the various phenomena in the ionosphere, TEC (Total Electron Content) is responsible for range error which produces a time delay in the radio signal. The rate of change of TEC with respect to time is abbreviated as ROT. It is one of the parameters that express the ionospheric irregularities with respect to time. This work investigates the effect of ROT fluctuation on the precise positioning of GPS receivers during low solar activity periods in the equatorial anomaly region. Good geometry and a sufficient number of locked satellites provide more accuracy within the centimeter level, but the case may be different when there are any ionospheric storms. Even a few satellite signals passing through the ionospheric irregularities can cause a significant error in positioning. Thus, it is important to understand the ionospheric irregularities observed by GPS receivers in order to correct them. The ROT (TEC/Minute) parameter is used here to study the occurrence of TEC fluctuation and its potential effect on GPS, such as a horizontal positional error or the satellite geometry of the GPS receiver. This investigation is based on the analysis of a one-year observation of a fixed GPS receiver installed at Bhopal (23.2020N, 77.4520E), India during low solar active period in 2005. The GPS receiver used here is a GISTM-based dual frequency NovAtel OEM4 GPS receiver.
Highlights
The ionosphere is a region of charged particles: ions and electrons; that ranges from 50 Km to 1000 Km
Their effect on the precise positioning of the satellite geometry of the NovAtel GPS receiver has been considered in both cases
The impact of this storm can be seen on the rate of change of Total Electron Content (TEC), as shown in the form of RMS of the rate of change of VTEC (ROT)
Summary
The ionosphere is a region of charged particles: ions and electrons; that ranges from 50 Km to 1000 Km. Our study aims to establish the amount of ionospheric irregularities, the rate of change of TEC observed from several satellites together, as well as the resultant effects on horizontal errors in easting and northing. Since the GPS receiver used here for experimentation was fixed and surveyed for about two years in various ionospheric conditions, its use eliminates each possible error in positioning We take this point as a fixed GPS point which is mounted on the roof of the Space Science Laboratory, Department of Physics, as shown by satellite picture in Fig. To study the effect of the ionosphere on the GPS receiver, a rate of change TEC (ROT) of 1 min is calculated by using Eq 2. When using ROT, we avoid the problem of phase ambiguities
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