TITLE:
The Status of the Gravimetric Geoid across Nigeria
AUTHORS:
Kurotamuno Peace Jackson, Lawrence Hart
KEYWORDS:
Fast Fourier Transform, Gravimetric Geoid, Height Anomalies, Hybrid-Geoid, Residual Terrain Model
JOURNAL NAME:
International Journal of Geosciences,
Vol.17 No.1,
January
29,
2026
ABSTRACT: Orthometric heights are obtained by Spirit leveling; however, this approach is not only slow but is also costly and time-consuming. Therefore, the uncertainties in the accuracy of geoid height models have hampered the use of GNSS heightening as an alternative method of determining Orthometric heights across Nigeria. This study was aimed at appraising the status of the geoid model in Nigeria based on gravity measurements, applying the remove-compute-restore (r-c-r) approach through the Fast Fourier Transform (FFT) tool. The GRAVSOFT tool was used in evaluating the residual height anomalies and terrain effects resulting from the residual terrain model (RTM). The residual height anomalies, (ζres) were computed by applying the modified Molodenskii Integral tampered 100% zero padding so as to overcome cyclic effects. The residual height anomalies were converted to geoid undulation by adding the ζ-to-N correction. The study revealed that, the difference between the height anomaly (ζ) and the geoid height (N) is about 24 cm and the geoid values across Nigeria range between 13.738 m and 26.052 m. There is a tilt of the geoid from the South-west to North-west part of the country. The gravimetric geoid is accurate to ±41 cm rmse when compared with the geometric geoid while the surface fitting revealed that the hybrid-geoid is accurate to ±3 cm rmse.