Correction of Measured Gravity Tides with FG5 Absolute Gravimeter Observations

The tidal correction on data recorded with FG5 absolute gravimeter is investigated in the study using gravity tides observed with a superconducting gravimeter iGrav-012 installed at Beijing Changping station, National Institute of Metrology, China. The difference between measured synthetic gravity tidal and theoretical synthetic gravity tidal obtained by high precision superconducting gravimeter is analyzed. Two kinds of measured data obtained by iGrav-012 superconducting gravimeter and FG5X-249 absolute gravimeter were used to verify the correction effect of measured tides.Numerical results show that the difference between the observed gravity tides and the theoretical gravity tides considering ocean loading effect is less than 1 μGal, which is lower than the observed accuracy of FG5 gravimeter. As a conclusion, it is not necessary to consider the tidal correction with observed tides from the view of the observed accuracy. However, the results from the FG5X-249 absolute gravimeter indicate that different methods of tidal correction can change the absolute gravity value itself. Although this change is very small and at the order of 0.1 μGal, tidal correction using observed tide is still recommended in precise absolute gravimetry.