Atmospheric Correction of FG5 Absolute Gravimetry Data using Measured Air Pressure

Abstract

Abstract Changes in atmospheric pressure affect atmospheric density, which is a key factor affecting high-precision gravity measurement. Currently, atmospheric correction of absolute gravity measurements uses the empirical admittance value recommended by the International Association of Geodesy (− 0.3 µGal/mbar); however, the actual admittance value changes with atmospheric mass and time. In this study, we determine the effect of using measured admittance values for absolute gravity correction. First, high-precision relative gravimeters (OSG-057, CG5) are used for continuous gravity measurement. Then, air pressure measured by the FG5 absolute gravimeter is used to obtain the atmospheric admittance using the iterative least squares method, which is compared with the theoretical atmospheric admittance. Taking FG5-257 as an example, we use the measured admittance for atmospheric correction of absolute gravity at four different elevations (Lhasa, Nagqu, Gar, and Suining, China). The results are as follows. 1) FG5-257 can accurately calibrate the Lhasa OSG-057 superconducting gravimeter with precision of 0.01% and a scale factor of − 77.001 ± 0.007µGal/V. 2) According to co-location measurements in Lhasa, CG5 and OSG measured admittance values exhibit comparable precision (0.332 ± 0.0029 µGal/mbar and − 0.332 ± 0.0004 µGal/mbar, respectively), indicating that the time-variable gravity field can be obtained by CG5 without co-location with superconductive gravimeters. 3) After correction using the measured admittance, changes in inter-group dispersion and measurement precision are approximately 0.01 µGal; however, the effect on the measurement results does not exceed 1 µGal, which is equivalent to the measurement precision of FG5. Therefore, measured admittance values are only recommended for atmospheric correction of high-precision absolute gravity measurements.