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% for vertical components are observed in BDS-only and BDS/Galileo/GPS PPP-IAR solutions with ZTD augmentation, while those for PPP float solutions are marginal. Additionally, 2-h positioning arcs for PPP float solutions and 1224 10-min arcs for PPP-IAR solutions confirm that ZTD augmentation plays an important role in convergence, especially for PPP-IAR solutions. The percentage of instantaneous convergence in BDS-only PPP-IAR solutions improves from 42.1, 44.0 and 18.9% to 51.3, 52.3 and 48.9% for the east, north and up components, respectively, indicating that decorrelation between ZTD and vertical coordinates can be achieved with MOFC ZTD corrections in the initial stage of positioning. The percentages further improved from 89.7, 89.5 and 74.6% to 94.1, 94.2 and 93.7% for BDS/Galileo/GPS PPP-IAR solutions. [ABSTRACT FROM AUTHOR]