Applicability of Klobuchar Model for STEC Estimation Over Thailand Region

Abstract

In the current study, we investigated the total electron content (TEC) variations over Thailand region by using five multi-constellation Global Navigation satellite system (GNSS) signals. The STEC variations for all multiple GNSSs were computed with well-known ionospheric Klobuchar model and compared with the STEC values of Global Ionospheric map (GIM) on a storm day (May 12, 2021), before as well as after this storm day. The results showed that most of the GIM STEC values (GSVs) were overestimated with the Klobuchar model STEC values (KMSVs) for all constellations, except QZSS. As for the QZSS, the KMSVs were closest to the GSVs. Likewise, the MS-SHF-based Klobuchar model (MSSHFKM method) was able to compensate the ionospheric delay effectively as compared to the original Klobuchar model up to 77.08% RMSE during the geomagnetic storm on May 12, 2021.