Insight into the Global Gravity Models for Free-Air Gravity Estimation using Land Gravity Data

Abstract

Gravity anomalies are used for the interpretation of the structures which are beneath the Earth. The availability of gravity anomalies at the early stage of exploration activities makes determining characteristics, forms and location properties beneath the Earth’s crust possible. Different GGMs have different accuracies due to factors such as differences in sources of data and the mode of their formulation. It is essential to know the efficiency of models over an area before being used for serious activity over the area. This research evaluated gravity anomaly derived from Global Gravity Models to determine the best-fit model over Akure City, Nigeria, by accessing ten gravitational models over twenty-three geodetic control points. Free-Air was the Gravity field model, calculated through the ten Global Gravity field Models over the study area. The computations of the anomalies were done at the International Centre for Global Earth Models (ICGEM). Terrestrial gravity anomaly data acquired was the standard against the ten model-based gravity anomalies using a coefficient of correlation and T-test to determine the best models over the area. Based on correlation analysis, SGG_UGM_2 has a value of 0.5995, and EGM2008 was 0.5973, respectively. The two models are the best fit for the study area. Based on the T-test for Free-Air anomaly data, EGM2008 and GECO have no significant difference from the terrestrial gravity models having P-values of 0.0393 mgal and 0.0146 mgal, respectively. This research, therefore, underscores the significance of adopting the best-fit model over the study area.

Keywords

• coastal erosion
• Lagos
• remote sensing
• shoreline forecast
• Synthetic Aperture Radar (SAR)