Validation of high-resolution global geopotential models over Sri Lanka using ground gravity & GPS-levelling data
Keywords:Global geopotential models, Gravity data, GPS-levelling data
With the advent of new gravity-dedicated satellite missions (CHAMP, GRACE, and GOCE), the long wavelength gravity field modelling of the Earth is possible with remarkable accuracy. Numerous global geopotential models (GGMs) have been developed to date with improved satellite gravity information, enhanced land gravity and satellite altimeter data. In the recent past, high-resolution GGMs (HR-GGM) have been developed with significant accuracy. They can be useful for local and regional geodetic and geophysical applications, especially in areas with a lack of ground gravity data coverage. Inaccuracy analysis of GGMs is vital before using them in geodetic or geophysical applications. In this study, five HR-GGMs are evaluated against the absolute gravity, Bouguer anomaly and GPS-levelling data in Sri Lanka. Two regions with flat and rugged terrain, Jaffna and Bandarawela, were utilized to investigate their variations appropriately. Analysis of gravity and Bouguer anomaly revealed that even high-resolution global models are not capable of representing features in rugged mountainous areas because of the omission errors resulted due to the truncation of the model’s gravity field at its maximum degree and order, but fitted quite well with flat terrain. A clear bias around 1.6 m of Sri Lankan GPS-levelling datum can be seen through the results of geoid height analysis of high mean values and comparatively low standard deviations. Overall, the recently released SGGUGM-2 model shows a better agreement with ground gravity and GPS-levelling data in Sri Lanka.