Ocean Tide Loading Effect on GPS Precise Positioning

Ocean tide loading has a crucial geophysical effect on GPS precise positioning.Based on the theory of ocean tide loading,ocean tide loading displacements for IGS stationsin China and surrounding areas resulting from four global ocean tide models are calculated,and their influences on GPS daily and sub-daily solution are analyzed and compared.For dai-ly solution for the station,results show that ocean loading displacement corrections lead tothe same RMS for the daily solution residuals with no corrections on average,but for RMSsof daily solution residuals in the vertical direction,there are changes in coastal areas,so it isbelieved that four ocean tide models have insufficient accuracy for the offshore area of theYellow Sea and the East China Sea,and must be corrected by the data for the China offshoreregional ocean tide.For sub-daily solutions for the stations,results show that the ocean tideloading effect decreases with the distance of the station from the sea.Particularly in coastalareas,the accuracy of the vertical coordinates of the station can be significantly improved,soocean tide loading displacement corrections should be considered in sub-daily GPS precise po-sitioning.