A geodetic datum is a system of latitude and longitude coordinates and reference points that is used to locate places on the Earth.
Australia is in the process of changing to a new official geodetic datum called the Geocentric Datum of Australia 2020 (GDA2020) which is replacing the current Geocentric Datum of Australia 1994 (GDA94). GDA94 was preceded by Australia's first official national datum called the Australian Geodetic Datum. It had two versions - Australian Geodetic Datum 1966 (AGD66) and Australian Geodetic Datum 1984 (AGD84).
The changeover is implemented individually within each jurisdiction with national coordination facilitated by ICSM. The GDA Modernization Implementation Working Group within ICSM was formed to manage that coordination. For more information about the change, seehttp://www.icsm.gov.au/gda/index.html
The new implementation of GDA2020 and the associated datum transformations are available by using the coordinate system files supplied in AutoCAD Map 3D toolset.