Ionospheric TEC and ROT Analysis with Signal Combinations of QZSS Satellites in the Korean Peninsula

This study investigates the performance of three different signal combinations (L1-L2, L1-L5, and L2-L5) for estimating ionospheric Total Electron Content (TEC) and rate of TEC (ROT) using Quasi-Zenith Satellite System (QZSS) observations over the Korean Peninsula. GNSS data collected from nine stations across the Korean Peninsula were analyzed for the period from Day of Year (DOY) 1 to 182 in 2024. Differential Code Biases (DCBs) were estimated for QZSS satellites using a regional ionospheric model, showing high temporal stability. TEC values derived from different signal combinations were compared with the CODE Global Ionospheric Map (GIM). The L1-L5 combination yields the closest agreement with the CODE GIM in terms of both bias and root mean square (RMS) error. In addition, the ROT analysis over the consecutive six days revealed that the L1-L5 combination consistently exhibited the lowest RMS values. As a result, we suggest that the L1-L5 combination can provide better performance for QZSS-based ionospheric monitoring and TEC studies.