A Global Vertical Reference Frame Based on Four Regional Vertical Datums

A Global Vertical Reference Frame (GVRF) has been realized by means of several regional and local vertical datums (LVD) distributed world-wide: the North American Vertical Datum 1988 (NAVD 88), Australian Height Datum 1971 (AHD 71), LVD France, Institute Géographique National 1969 (IGN 69) and Brazilian Height Datum 1957 (BHD 57). The vertical shifts of the above LVD origins have been related to the adopted reference geopotential value W₀ = (62 636 856.0 ± 0.5) m²s^–2 and they were determined at the 5 cm level. However, the W₀ reference value can be chosen arbitrarily, the methodology, which was developed here, does not require that the above value be adopted.