A case study of geoid modeling in Sulawesi and accuracy verification strategies for accommodating diverse MSL vertical datums

Abstract This study aims to introduce the geoid modeling process in Sulawesi and demonstrate the practical issues faced. There are limitations of terrestrial gravity surveys in Sulawesi due to its complex geography, so airborne gravity surveys were conducted from 2008 to 2019 through a collaboration between the Badan Informasi Geospasial (BIG), the Technical University of Denmark (DTU), and the National Chiao Tung University (NCTU) gravity research team. The airborne gravity data currently cover almost the entire land area of Indonesia. The geoid modeling process involved refining the EGM08-derived geoid heights by incorporating downward-continued airborne gravity data and RTM-derived geoid effects, and adjusting the geometric geoid heights to accommodate diverse mean sea levels used in different GPS/leveling datasets. The impacts of different global gravitational models (GGMs), such as EIGEN-6C4, GECO, XGM2019e, and SGG-UGM-2, on geoid modeling were examined, and it revealed that differences arise from the different datasets used in the development of the GGM. This study revealed that airborne gravity data can significantly improve the accuracy of the geoid, achieving an impressive accuracy of approximately 0.04 to 0.05 m. In addition, the compatibility issue between gravity data and GGM in geoid modeling is highlighted. The strategy to unify the vertical datum between different GPS/leveling datasets for the validation of gravimetric geoid model was discussed in detail. Once the corresponding geopotential is determined, the conversion between the global vertical datum and the local vertical datum can be achieved. Accurate geoid is critical for infrastructure development, land-use planning, and resource management and play an integral role in supporting sustainable development goals (SDGs) by providing accurate spatial referencing, ensuring precise mapping, and offering location-based services.