COMPARATIVE ANALYSIS OF ORTHOMETRIC HEIGHTS OBTAINED FROM GNSS, SSG-UGM, TONGJI-GGM2021S, EUGEN-GRS

ABSTRACT Although satellite data integration has advanced significantly, global models often fall short in achieving the accuracy required in regions with high relief or complex geological features, which highlights the importance of localized geoid models. In the Federal Polytechnic Ado-Ekiti region, limited research on the performance of Global Geopotential Models (GGMs) for local geoid computation makes it difficult for surveyors and geodesists to select the most suitable model for accurate height conversion. This study evaluates the performance of three GGMs—XGM2019e, EIGEN GRS, and TONGI 2021—by determining orthometric heights in the Federal Polytechnic Ado-Ekiti region. Geoidal undulation values for 38 selected points were derived by inputting the processed geodetic coordinates into the "User-Defined Points" service on the ICGEM website, which provided geoidal heights for each model. An Analysis of Variance (ANOVA) was conducted to assess the statistical differences between the GGMs. The results revealed no significant differences in orthometric heights among the models, although TONGI 2021 exhibited slightly better accuracy with lower variance. Consequently, the null hypothesis was accepted, indicating statistical similarity in the heights computed by the three models. TONGI 2021 is recommended as the most reliable GGM for local geoid modeling. Periodic model reassessment and the integration of local gravity data are suggested to ensure continued accuracy in future geodetic work. Keywords: Global Geopotential Models (GGMs), Geoid Models, Orthometric Heights, Geoidal Undulation, GNSS Measurements, ANOVA, Height Conversion, ICGEM