Real-time regional tropospheric wet delay modeling and augmentation performance for triple-frequency PPP/PPP-IAR during typhoon weather

Troposphere augmentation is of great importance for global navigation satellite system (GNSS) real-time precise point positioning (PPP) service. This contribution focuses on the feasibility of modeling the regional troposphere by polynomial fitting and the benefits of precise tropospheric corrections for triple-frequency and multi-GNSS PPP and PPP with integer ambiguity resolution (PPP-IAR) during a period of typhoon weather. A modified optimal fitting coefficient (MOFC) method is proposed with the height-related parameters removed by a priori fitted exponential function. Two spatial scales of networks are chosen to verify the effect of the GNSS station distribution on troposphere modeling. The results show that the MOFC model can provide centimeter-level accuracy with average root mean square (RMS) of 2.1 and 2.2 cm for dense and sparse networks, respectively, while that of GPT2w and real-time VMF3-FC products are 6.6 and 3.3 cm during typhoon periods. PPP/PPP-IAR tests with zenith troposphere delay (ZTD) augmentation based on the MOFC model are conducted when a typhoon eye passes over. Accuracy improvements of 18.2 and 16.6