Unifying the Irish Vertical Datum with the Normaal Amsterdams Peil (NAP)

Abstract

The local gravity potential value on Malin-Head tide gauge station in Ireland is derived from gravimetric and geometric geoid undulations. The geometric geoid undulations are obtained from GNSS and levelling data. In contrast, the gravimetric geoid undulations are computed based upon their long-wavelength components using the GOCE gravity field model, and their short-wavelength components using the terrestrial data through the Remove-Compute-Restore technique. The potential value obtained from the combination of the satellite-only gravity field model GOCO06s up to degree/order 245, and terrestrial + EGM2008 data for the local tide-gauge station in Malin-Head, is computed as 62 636 858.273 m2/s2, and is recommended as the present best estimate value in Ireland. The local gravity potential value on Malin-Head tide gauge station differs by 0.363 m2/s2 from the gravity potential value of EGG2015, (62 636 857.91 m2/s2), and is equivalent to height differences equal to 0.034 m above Normaal Amsterdams Peil (NAP) datum.