Computation of a Gravimetric Geoid Within the Kingdom of Saudi Arabia (KSA) by Least-Squares Collocation

Abstract

A gravimetric geoid for the Kingdom of Saudi Arabia (KSA) is computed by least-squares collocation (LSC) with the remove–compute–restore technique. Approximately 3657 free anomalies distributed across the region are used. Free anomalies are first referenced to a combined earth geopotential model (EGM) that was obtained by merging the GOCE_DIR-R5 satellite-only model and earth geopotential model 2008 (EGM2008). Then, residual terrain model (RTM) effects based on the Shuttle Radar Topography Mission SRTM30_PLUS are reduced based on the free anomalies. The reduced free anomalies are used in LSC to compute reduced geoid heights; thus, restoring both EGM and RTM effects on geoid results in a gravimetric geoid range from − 37.513 m in the southeast region to 23.183 m in the northwest region. The accuracy of the estimated gravimetric geoid, as shown by the standard deviation of the geoid heights, varies from ± 0.115 to ± 0.612 m. Our statistical analysis shows that the estimated geoid reduced the errors by approximately 23% and 7–8% on the pointwise and gridwise scales, respectively. Comparisons show the consistency of the computed gravimetric geoid with GNSS/levelling geoid heights at 802 benchmarks. In mountainous areas, differences between the gravimetric and GPS/levelling geoids reach as much as a few decimetres. The first user interface to be released is called KSAGH01, and it is developed using the appropriate interpolation method with user coordinates.