Temporal and Spatial Impact of Precipitable Water Vapor on GPS Relative Positioning During the Tropical Cyclone Hato (2017) in Hong Kong and Taiwan

The evident disturbance of global positioning system (GPS) positioning results responding to the 2017 tropical cyclone (TC) Hato is observed in both Hong Kong and Taiwan regions. The GPS solutions of 10 baselines, i.e., five from Hong Kong and five from Taiwan, with baseline lengths ranging from 4.8 to 46.6 km, are analyzed during the TC period from August 16 to 26, 2017. The precipitable water vapor (PWV) variation in temporal and spatial domains is also investigated in terms of 2–5 h scale-averaged wavelet power and normalized magnitude of spatial gradient. The results indicate that there is a close correlation between positioning disturbance and the spatiotemporal variation of PWV during the TC period. The daily Spearman’s correlation coefficient on TC-impacted day is 0.65 for Hong Kong baselines, ∼1.97 times as large as the mean value 0.33 of the non-TC-impacted period. Furthermore, the positioning performance started to degrade when the normalized magnitude of the spatial gradient of PWV experienced a rapid increase. The degradation lasted for ∼7 h, and the degrading trend for Hong Kong baselines is 9.86 mm/h on average. For Taiwan baselines, the degradation lasted for ∼31 h, and the degrading trend is 1.20 mm/h on average. In addition, the GPS three-dimensional positioning average accuracy on the TC-impacted day, July 22, 2017, degraded by 255% over the 10 baselines with respect to that of the other non-TC-impacted days.