Evaluation of the influence of the Global Geopotential Model resolution on the accuracy of local geoid models: (Case study: DI Yogyakarta Province)

Local gravimetric geoid determination requires data comprising three components namely long-wavelength, medium-wavelength, and short-wavelength components. The long-wavelength component is derived from the Global Geopotential Model (GGM). The medium-wavelength is obtained from terrestrial gravity data, and the short-wavelength component is derived from Digital Terrain Model (DTM) data. Among these three components, the GGM data contributes the most significant value and error. This study has evaluated the influence of the GGM resolution on local geoid model for the area with a good and dense terrestrial gravity data distribution, case study in Yogyakarta Special Region (DIY). This evaluation was carried out to determine the optimal degree value of the GGM for local geoid modelling. The gravimetric geoid computation was done using 2D FFT (Fast Fourier Transform). The utilized variation of the degree values were 360, 540, 720, 1080, 1440, 1800, 2160 and 2190 of the EGM2008 data. The evaluation of the variation of the GGM degree values contribution to the local geoid modelling was done using the geometric geoid derived from collocated GPS-levelling data. The results showed that using the lowest degree value (360 degree) produces the optimal (best) local geoid accuracy for the case study of DIY province.