Prospects for the Australian Height Datum and Geoid Model

Abstract

The integrity of the Australian Height Datum (AHD) has remained in some question ever since its adoption in 1971. Indeed, its creators commented that using 30 tide gauges ‘placed a strain’ on the least-squares network adjustment of the —97,230 km of spirit levelling used to realise the AHD. Although the AHD seems to have served Australians well, the question remains — can the AHD be improved? Of course, re-levelling an entire continent the size of Australia is prohibitively expensive, especially in the current climate of economic rationalism. Therefore, a proposal is made to enhance and redefine the AHD using the additional levelling data collected since 1971, mean sea level observations made at new tide gauges, models of the sea-surface topography, nation-wide GPS height networks and a regionally refined gravimetric geoid model. This proposal is balanced against the arguments in favour of retaining the existing AHD, coupled with a geoid model that has been warped to fit the existing AHD using nation-wide GPS networks co-located with AHD benchmarks.