The Effect of Local Tide on Precision Positioning in Shanghai

In view of the differences of the global tidal model in different coastal areas and the poor accuracy of offshore in China,using the global tide models FES2004 and NAO99b to calculate the vertical component of the tidal load displacements of the four tide components S₂、M₂、K₁and O₁ in Shanghai (The range from 120.85 to 122.2 East longitude, 30.6667 to 31.8833 West latitude).In order to calculate the effect of local tide on the precise positioning of four stations of SHJZ station (Shanghai Jinshan), SHJBS station (Shanghai Baoshan), SHAO station (Shanghai Sheshan) and DCMD station (Shanghai Chongming), using the Chinese offshore model osu.chinasea.2010 to replace the corresponding region in the global tide model FES2004.The results show that: (1)There are obvious differences between the global tide models FES2004 and NAO99b in Shanghai, especially in the vertical components. The maximum is close to 4 mm, and the difference between the two models decreases with the distance from the ocean;(2)The influence of offshore effect on the precision positioning of GPS stations in Shanghai reaches 5 mm,and the influence on the vertical component of the station from big to small are DCMD station (5.1 mm), SHBS station (4.9 mm), SHJS (4.2 mm) and SHAO (3.6 mm) respectively.