Methodological Investigation of the Processing of Absolute Gravity Data

Abstract

This paper is devoted to the influence of several parameters (modelling of solid and ocean tides, air pressure, vertical gradient, site conditions) affecting the determination of the value of the absolute gravity. The confidence in the results relies on the dependence of the gravity (mean value and time-varying residues) on small changes in these parameters and the way we can constrain our choice of them. With the help of data sets obtained from absolute gravimeter (AG) FG5#206 at different stations, we will thus study the influence of i) the modelling of solid tides by the use of several models based on recent tidal developments, ii) the modelling of the oceanic loading tides including models derived from satellite altimetry, iii) the modelling of the pressure correction by the use of a local barometric admittance value versus a global loading computation, iv) the vertical gradient (do we have to measure it each time or is it better to use always the same value even if it is a theoretical one?). A methodological investigation of the consequences of these corrections will help answering the fundamental question of the duration which is needed in order to achieve convergence in the mean g value. We will also show the impact on the gravity residues of these parameters.