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Ionospheric effect on GPS-based marine navigation
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Dr Rajesh Tiwari
Dr Smita Tiwari
Tiwari R, Tiwari S, Bhattacharya S, Purohit PK, Gwal AK
Journal of Engineering, Science and Management Education
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The marine navigation is one of the major applications of GPS-based navigation, and it require high level of precision, availability and reliability. However, the precision does depend on ionospheric conditions. The performance of GPS is not so effective in low and high latitude region. The ionosphere is composed of non-uniform charged particles, so it has different properties depending on geomagnetic latitude, season, and local time. GPS signal slows down in the ionospheric region with
the actual velocity of light. A delay of about 5 – l00 ns in the zenith direction may be observed. The extra ionospheric delay produces a range error, which ultimately affect position accuracy. In this research paper, influence of the ionosphere on GPS accuracy over geomagnetic latitude (high, mid, and low latitude) has been investigated in dynamic mode for marine navigation in M.V. Emerald Sea, a Russian cargo ship during XXVI Indian Scientific Expedition for Antarctica (ISEA). A close correlation of magnitude of the rate of change of TEC (ROT) is established with navigational solution over three different geomagnetic regions. The ROT parameter is represented as ionospheric irregularities, and it also represents as GPS phase fluctuation. In this study, it is observed that high level of fluctuation in ROT effect the position solution. The higher fluctuation recorded in low- and high-latitude regions, and so as position errors, and sometime exceeding tolerable limits. Furthermore, the study also agree with theory of ionospheric disturbance is high in high and low geomagnetic region, whereas the mid-latitude seems to be moderate and the level of degradation of position solution in mid-latitude is comparatively lower.
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