Development of the National Gravimetric Geoid Model for the Kingdom of Saudi Arabia

AbstractThe development of a high-resolution and high accuracy geoid model is becoming nowadays a fundamental component of any modern geodetic infrastructure. The Kingdom of Saudi Arabia (KSA) has devoted the last decade a significant number of resources and manpower to collect high-quality land and airborne gravity data as well as GNSS/Levelling observations to create a state-of-the-art geoid model as a fundamental part of the Saudi Arabia National Spatial Reference System (SANSRS). In that frame, this work focuses on the collected gravity, terrain, and GNSS/Levelling data for the area under study, and their pre-processing in terms of horizontal, vertical and gravity reference system homogenization, blunder detection and removal. Given the availability of these data the latest gravimetric geoid model for the KSA is developed.The gravity data pre-processing relied on the available metadata to collect information about the horizontal, vertical and gravity reference system. Hence, all this information has been homogenized to KSA-GRF17, tied to ITRF2014 at epoch 2017.0, and KSA-VRF14 which is tied to the geopotential number above the MSL of the Jeddah TGBM-B. Given that several data holdings of land gravity where either in the form of Bouguer anomalies or referred to some unknown horizontal datum, several tests have been carried out to identify the proper choices. Then, a least-squares collocation-based blunder detection and removal procedure has been conducted to identify blunders in the land data and possible biases between the various campaigns and the high-quality airborne gravity observations. The geoid prediction was carried out by the well-known remove-compute-restore technique evaluating Stokes’ integral in the frequency domain via a 2D spherical Fast Fourier Transform and the Wang-Gore modification. After several tests with the latest GOCE/GRACE-based and combined Global Geopotential Models, XGM2019e has been used as a reference, while the residual terrain model correction was employed for the treatment of the topography. The validation of such a developed gravimetric geoid model has been performed for a set of ~4,500 GNSS/Leveling benchmarks reaching external absolute accuracies at the 10–11 cm level and relative accuracies at the 1–5 ppm over distances ranging from 10 to 2,000 km.