Sea surface topography (dynamic ocean topography) effects on the Australian Height Datum

The Australian Height Datum (AHD) forms the vertical spatial data framework for Australia. It was established in 1971 through the least-squares adjustment of >190,000km of spirit levelling and was adjusted to zero MSL at 30 tide gauges. The un-modelled sea surface topography (dynamic ocean topography) seems to have caused distortions in the AHD, and we plan to improve the AHD in the longer term.