An assessment of the mass line and mass prism models in terrain correction for regional geoid modelling in low mountainous areas

Abstract

Terrain correction is a very crucial step in gravity reduction and the reliability of the adopted topographic model plays a significant role in the overall geoid computation process especially in mountainous terrain. Given the cumbersome computation involved in the mass prism model, the mass line topographic model is often utilized in practical computation while implementing terrain correction for most gravity reduction schemes. In this study, an assessment is made of the accuracy of the mass line (ML) model viz a viz the mass prism (MP) model in a low-ranged mountainous area like Ado Ekiti township; with a view to determine the suitability of the continued use of ML in such regions. Both models were implemented in the spatial domain using MATLab codes written from the conventional formulae. Results obtained indicate that the minimum and maximum differences in computed Bouguer anomalies using ML and MP models are 0.0196mgals - 0.0610mgals. Consequently, the choice of model did not have significant effect on the computed geoid models as the derived geoid from both models produced the same RMSE of 83cm when compared with GNSS-Leveling geoid at validation points. The study concludes that for topographic ranges less than 300m, either of both topographic models could be used and similar level of accuracy will be obtained in the resulting geoid.