Determination of Indonesia’s Marine Deflection of Vertical from Multi-Mission Altimetry Satellite Data

The deflection of vertical (DOV) is important for studying the changes in the Earth’s mass, improving the accuracy of geoid models, and the accuracy of the Earth’s gravity field. Compared to traditional methods such as astrogeodesy and astrogravimetry measurements, altimetry satellites have the advantage of observing DOV due to uniform global distribution, denser measurement points, consistent precision, less time required, high temporal resolution, and can be used in all weather conditions. In this study, multi-mission altimetry satellites including TOPEX/Poseidon, Jason-1, Jason-2, Jason-3, ENVISAT, Geosat Follow On (GFO), Sentinel-3A, Sentinel-3B, Sentinel-6A, Cryosat-2, and SARAL were used to determine DOV in Indonesia’s marine with a spatial resolution of 1’ x 1’. The Hwang et al. (1998) method is used to calculate DOV from satellite altimetry data by least-squares adjustment with weights using the second-order inverse distance weighting (IDW) method for each grid. The results show that the variance of the north-south and west-east components resulting from the gridding results are 0.05 arcseconds and 1.2 arcseconds. The evaluation results with the global model from EGM2008 show that the standard deviation values for the north-south and west-east components are 0.63 arcseconds and 1.96 arcseconds, respectively. From the evaluation, it can be concluded that the gridded DOV model is close to EGM2008, but there are still challenges for improvement, especially for the west-east DOV component.