Hybrid Geoid Modeling for the Kingdom of Saudi Arabia

Abstract

AbstractA significant improvement in the accuracy and homogeneity has been achieved with the new gravimetric geoid model for the Kingdom of Saudi Arabia (KSA-Geoid21GRAV) w.r.t the previous Geoid models KSA2009, KSA2015 and KSA-Geoid17. The gravimetric geoid prediction was carried with the remove-compute-restore technique resulting in external absolute accuracies at the 10–11 cm level and relative accuracies at the 1–5 ppm. In this work, the estimation of the hybrid KSA-Geoid21 model is described. A hybrid deterministic and stochastic approach is used to model the residuals of the gravimetric model relative to available GNSS/Levelling geoid heights. Various parametric models ranging from simple north-south bias and tilt one to second and third degree polynomial models have been evaluated. After various tests a second order polynomial model was selected resulting in a 10.3 cm absolute difference of the adjusted residuals between the gravimetric KSA-Geoid21 geoid model and the GNSS/Levelling geoid heights. Following that, a stochastic modelling of the residuals after the fit has been carried out, resulting in errors relative to the GNSS/Levelling data at the 0.014 m level. Compared to the previous geoid model, KSA-Geoid2017, improved residuals to 75.2% of the benchmarks is found with a mean improvement at the 1.1 cm, while for the rest 24.8% a mean deterioration of 0.7 cm is found.