Analysis of Ionospheric TEC and DCB Using GPS/Galileo Observations from a Moving Training Ship

This study investigates ionospheric total electron content (TEC) and differential code bias (DCB) based on GPS and Galileo data collected aboard the training ship (HANS) from DOY 249 to 300 in 2024. The estimated TEC was compared with the Center for Orbit Determination in Europe (CODE) global ionospheric map (GIM), resulting in a mean difference of –2.41 TEC units (TECU) and a root mean square (RMS) error of 6.53 TECU. Furthermore, although inland GNSS stations in South Korea were incorporated to stabilize receiver DCB estimation, the results still exhibited significant temporal fluctuations. The Pearson correlation revealed a moderate negative relationship between the receiver DCB change and the Dst index, with a correlation coefficient (R) of –0.35. It suggests that geomagnetic disturbances influence receiver DCB changes. The R between receiver DCB and the Kp index was approximately 0.18, while that with the F10.7a index was about –0.26, both indicating a relatively weak correlation. In addition, receiver DCB changes exhibited a positive correlation (R ~ 0.33) with vertical TEC (VTEC). Multipath errors showed negligible correlation with receiver DCB changes. Therefore, we suggest that the significant variability in the receiver DCB on the HANS has a strong correlation with the Dst and VTEC. It can also be attributed to the complex interaction of several factors.