A new method of improving global geopotential models regionally using GNSS/levelling data

In this paper, a new method for regionally improving global geopotential models (GGMs) with global navigation satellite system (GNSS)/levelling data is proposed. In this method, the GNNS/levelling data are at first converted to disturbing potential data with inverse Bruns' formula. Then the systematic errors in disturbing potential data are removed with a three-parameter correction surface. Afterwards, the disturbing potential data on the Earth's surface arc downward continued to the surface of an inner sphere with inverse Poisson's integral equation. Global disturbing potential data on the whole sphere could be achieved with combination of the downward continued data and the GGM-derived data. At last, the final regionally improved geopotential model (RIGM) could be recovered from the disturbing potential data using least-squares method. Four RIGM models for Qingdao (QD) are determined based on four different sets of GNSS/levelling data points to validate the capability of the method. The standard deviation of height anomaly errors of RIGM-QDs are nearly 25 and 30 per cent on average smaller than Earth Gravity Model 2008 (EGM2008) on checkpoints and data points, respectively. This means that the RIGM-QDs fit better to the GNSS/levelling network in this area than EGM2008. The results show that the proposed method is successful at improving GGMs in regional area with regional GNSS/levelling data.