Estimation of Geopotential Value W0 for the Geoid and Local Vertical Datum Parameters.

Unification of the global vertical datum has been a key problem to be solved for geodesy over a long period, and the main challenge for unifying the global vertical datum system is to determine the geopotential value W-0 of the geoid and to calculate the vertical offset between the local vertical datum and the global vertical datum W-0. The geopotential value W-0 can be calculated using the grid mean sea surface (GMSS) data and the global geopotential model (GGM). In this study, this GMSS data was measured with adjustment methods and 24 years of merged multi-satellite altimetry data. The data of HaiYang-2A (HY-2A) and Jason-3 were first used to calculate W-0. The geopotential value W-0 was determined to be 62,636,856.82 m(2)s(-2) by combining the EIGEN-6C4 (European Improved Gravity Model of the Earth by New Techniques) and the GMSS data. Then, the geopotential difference approach and geodetic boundary value problem (GBVP) approach were used to determine the vertical datum parameters in this study. To compensate for the omission error of the GGM, this study utilized the remove-compute-restore (RCR) technique and the residual terrain model (RTM)-recovered high-frequency gravity signals. Finally, as a result of the GBVP solution, the geopotential value of the Australian Height Datum (AHD) was 62,636,851.935 m(2)s(-2), and the vertical offset of the AHD relative to the global vertical datum W-0 was 0.4885 m. As a result of the geopotential difference approach, the geopotential value of the Chinese Height datum was 62636861.412 m(2)s(-2), and the vertical offset of the Chinese Height datum was -0.4592 m.