Seafloor Depth Mapping of Central Vietnam’s Sea area and its surrounding using gravity anomaly data and Gravity Geological Method

Seafloor topography mapping has a vital role in territorial management, geological investigation, natural hazard research, and marine construction; therefore, improving the accuracy of seafloor topography mapping is essential. The main objective of this research is to assess the possibility of improving the accuracy of seafloor topographic mapping for the central sea area of Vietnam and its surroundings based on the combination of satellite-derived gravity anomaly data and shipborne data. Firstly, the best satellite-derived gravity anomaly model for the study area is determined by comparing its gravity with the shipborne gravity anomaly. Then, the systematic deviation in the satellite-derived gravity anomaly is eliminated and fitted. Then, the substance density contrast (SDC) between the seabed and the seawater is derived. Subsequently, the seafloor depth was computed using the Gravity Geological method. In the next step, the computed depth is fitted with the shipborne depth to improve the accuracy and reduce the systematic deviation. The result shows that the best satellite-derived gravity anomaly model for the study area is the DTU17GRAV, with an accuracy of ±5.06 mGal. The most suitable SDC in the study area is 1.40 g/cm³. The final seafloor topographic map with 1'×1’ grid is obtained with the root mean square deviation (RMSD) of ±83.96 m, which is lower than that of the global terrain model of GEBCO 2022 (RMSD = ±152.88 m). Therefore, it is concluded that the combination of satellite-derived gravity anomaly and shipborne data can significantly improve the accuracy of seafloor mapping for complex topographic areas. The results of this research are helpful for seabed applications and territorial management in the region.