In GEONET, 35 CGPS stations are distributed near the radar scene (24 stations are in the inner, and 11 ones are around) (Fig. 1). The average baseline length of the stations is about 15 km. We process the GPS
observations with NASA/JPL GIPSY-OASIS (II) software (Webb and Zumberge, 1993). Using the precise point positioning (PPP) method, we extract the WZD parameter, including Drw and Drl in Eq. (1), series for 5-min interval. By the average of the parameters 2-before and 2-after the radar epoch, we obtain the WZD parameter at each station for the interferogram. Using the cosine mapping function, i.e. MðyÞ¼ cosð231Þ in (6), the line-of-sight wet delay (WSD) can be obtained (Fig. 1). The peak-to-peak WSD difference is 85.8 mm between S3039 and S3013.