Local geoid modeling in the central part of Java, Indonesia, using terrestrial-based gravity observations

The Global Navigation Satellite System (GNSS) positioning method has been significantly developed in geodetic surveying. However, the height obtained through GNSS observations is given in a geodetic height system that needs to be converted to orthometric height for engineering applications. Information on geoid height, which can be calculated using the global geopotential mode, is required to convert such GNSS observations into orthometric height. However, its accuracy is still insufficient for most engineering purposes. Therefore, a reliable geoid model is essential, especially in areas growing fast, e.g., the central part of Java, Indonesia. In this study, we modeled the local geoid model in the central part of Java, Indonesia, using terrestrial-based gravity observations. The Stokes' formula with the second Helmert's condensation method under the Remove-Compute-Restore approach was implemented to model the geoid. The comparison between our best-performing geoid model and GNSS/leveling observations showed that the standard deviation of the geoid height differences was estimated to be 4.4 cm. This geoid result outperformed the commonly adopted global model of EGM2008 with the estimated standard deviation of geoid height differences of 10.7 cm.