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

This study investigates ionospheric total electron content (TEC) estimation based on GPS and Galileo data collected aboard the training ship (HANS) from DOY 249 to 300 in 2024. The combined GPS/Galileo TEC is compared with the 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 are incorporated to stabilize receiver differential code bias (DCB) estimation, the results still exhibited significant temporal fluctuations. The relationship between the Dst indices and the GPS satellite DCB values is observed. In addition, the Pearson correlation (R) and a significance level (p) are considered to analyze the relationship between receiver DCB variations and some factors, such as geomagnetic indices (Dst, Kp, and F10.7a), vertical TEC (VTEC), and multipath error. Geomagnetic indices show no clear correlation. Furthermore, receiver DCB changes exhibit a weak correlation (R~0.33 and p~0.01) with VTEC. Multipath errors show negligible correlation with receiver DCB changes. Significant fluctuations in receiver DCB values prevent a clear correlation. Therefore, we suggest that there are inherent difficulties in precisely estimating ionospheric TEC and DCB values on a HANS trajectory.