Enhancing IGS All-Frequency Code OSB Products for Precise Point Positioning

The International GNSS Service (IGS) observable-specific signal bias (OSB) product is essential to all-frequency precise point positioning with ambiguity resolution (PPP-AR). In general, the code bias product generation precedes, rather than proceeds simultaneously with, the phase bias determination, and such a standard two-step estimation strategy could impair PPP-AR on those non-baseline frequency pairs (e.g., GPS L1/L5, Galileo E1/E6, BDS-3 B1C/B2a, etc.). In this study, we developed an approach to enhance the IGS code OSB products, which was interoperable and coupled with all-frequency phase bias determination. With 31 days of multi-GNSS data from about 380 stations in 2024, it was verified that representative IGS differential code bias products could differ remarkably by over 0.4 ns on average on the GPS/BDS-2/3 non-baseline frequency pairs. Once the CAS (Chinese Academy of Sciences) code OSBs were calibrated, however, the mean ambiguity fixing rates rose significantly from 70 to 90