Estimation and Assessment of Ionospheric Slant Total Electron Content (STEC) Using Dual-frequency NavIC Satellite System
DOI:
https://doi.org/10.13052/jgeu0975-1416.923Keywords:
Code range, Carrier range, NavIC, STEC, data pre-processing, Ionospheric delay.Abstract
Many atmospheric errors affect the positional accuracy of a satellite-based
navigation device, such as troposphere, ionosphere, multipath, and so on, but
the ionosphere is the most significant contributor to positional error. Since
the ionosphere’s dynamics are highly complex, especially in low latitude
and equatorial regions, a dual-frequency approach for calculating slant total
electron content (STEC) for ionospheric delay estimation performs better
in these conditions. However, the STEC is ambiguous and it cannot be
used directly for ionospheric delay prediction, accurate positioning purposes,
or ionospheric study. As a result, STEC estimation and pre-processing are
required steps prior to any positioning application. There is very little litera-
ture available for STEC pre-processing in the NavIC system, necessitating an
in-depth discussion. This paper focuses on how to extract navigational data from a raw binary file obtained from the Indian NavIC satellites, estimate and
pre-process STEC, and build a database for STEC. It has been found that an
hourly averaged STEC data is suitable for ionospheric studies and monthly
mean value can be used for ionospheric behavioral research. Furthermore, the
STEC is affected by diurnal solar activity, thus, the seven-month data analysis
that includes summer and winter months has been used to study ionosphere
action during the summer and winter months. It has been observed that STEC
values are higher during the summer months than the winter months; some
seasonal characteristics are also been found.
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