COMPARATIVE ANALYSIS OF LOCAL GEOID MODELLING IN HONG LOCAL GOVERNMENT AREA OF ADAMAWA STATE, NIGERIA

Abstract

This study evaluates the effectiveness of geometric and gravimetric approaches for determining geoid undulations and orthometric heights using integrated GPS/levelling data and selected Global Geopotential Models (GGMs). Three gravimetric technique: Stokes’ integral, the Simple Combine Method (SCM), and direct geoid extraction from GGMs were assessed using EGM2008, SGG-UGM-2, and XGM2019e_2156 models to identify the most reliable method for accurate height determination. Statistical measures, specifically mean values and standard deviations, were employed to examine accuracy, consistency, and clustering of the derived geoid and height solutions relative to spirit levelling observations. The results show that the SCM consistently produced the lowest standard deviations across all evaluated GGMs, indicating superior precision in geoid modelling. This improved performance is attributed to the method’s ability to effectively combine long-wavelength gravity information from GGMs with short-wavelength terrestrial gravity signals. Orthometric heights derived using the Stokes approach exhibited the closest agreement with spirit levelling, particularly when paired with the EGM2008 and SGG-UGM-2 models, demonstrating their suitability for regional height applications. Although XGM2019e_2156 offers enhanced global resolution, observed systematic shifts in orthometric heights suggest the need for regional adjustment before local use. Overall, the findings confirm that integrated geometric gravimetric approaches, especially the SCM combined with regionally appropriate GGMs, significantly enhance the accuracy and reliability of geoid and orthometric height determination.