Regional geoid-model-based vertical datums – some Australian perspectives

This article summarises some considerations surrounding a geoid-model-based vertical datum that have to be thought through before its implementation and adoption. Our examples are based on many Australian and some South-East Asian experiences, but these probably also apply elsewhere. Thekey considerations comprisedataquality andavailability, politics, anddifficulties thatusersmayencounterwhen adopting quite a different approach to height determination. We advocate some form of new vertical datum to replace the Australian Height Datum, but the exact type (whether using levelling or geoid, or some combination of both) still needs to be decided. We are not speci cally opposed to the adoption of a geoidmodel as the vertical datum, but it is possiblymore challenging than appears initially, and may even deter some users that are already well served by levelling-based vertical datums.