The method of tranfomation of seabed depth data from the international reference system to the national reference system

Abstract

The purpose of this study is to propose a method for tranformation of seabed depth data from the international reference system to the Vietnamese national reference system. Global seafloor bathymetric models have the latitude (B), longitude (L) of the points in the WGS-84 and the depth to the international mean dynamic topography (DQT). For tranformation of these coordinates and depths to the VN2000 and the national vertical system, it is necessary to determine the ellipsoid height (H) of the points in the WGS- 84 and the difference between the mean dynamic topography of Vietnam and the international mean dynamic topography. These ellipsoid heights are determined based on geoid height from the global Earth Gravity Model (EIGEN6C4); the international mean dynamic topography (DTU15MDT) and the international depth of the points. The difference between the national and international mean dynamic topography is determined based on data at 31 tidal gauge stations in Vietnam. After obtaining all coordinate components in the WGS84, the coordinates are tranformated using the Bursa-Wolf formula with 7 coordinate tranformation parameters between WGS-84 and VN2000. The experiments were calculated for the GEBCO2020 bathymetric model over the central East Sea.