Geocentric Datum of Australia 2020 (GDA2020)
Last updated:7 June 2023
There have been significant technology developments recently that provide ready access to accurate positioning systems. It is anticipated that the Global Navigation Satellite System (GNSS) will be capable of providing positioning services with centimetre accuracy in real-time to the mass market on mobile devices. Given that data from GNSS is referenced to a global reference frame, specifically the International Terrestrial Reference Frame 2014 (ITRF2014), it is appropriate that the Australian datum is closely aligned to the same global reference frame.
GDA2020 is based on a realisation of the ITRF2014 at epoch 2020.0, or 1 January 2020. This means the coordinates in Australia are projected forward to the date of 1 January 2020.
The Geocentric Datum of Australia 1994 (GDA94) was based on the realisation of ITRF1992 at epoch 1994.0, or 1 January 1994. Since then:
- due to plate tectonic motion, Australia has moved ~7 cm per year. As a result GDA94 coordinates have continued to diverge from ITRF92 coordinates. By 2020, the difference will be approximately 1.8 metres.
- there have been many improvements and realisations of the global reference frame which better defines the shape of the Earth. For example, differences between ITRF1992 and ITRF2014 (on which GDA2020 is based) cause a ~9 cm change in ellipsoidal heights in Australia (GDA2020 heights are ~9 cm less than GDA94 ellipsoidal heights)
- parts of the Australian crust have deformed (e.g. through subsidence and surface heave).
These refinements to the reference frame and many of the local scale distortions had not been reflected in changes to the Australian datum since GDA94.
GDA2020 provides a more robust and accurate datum which is more closely aligned to global positioning systems like GNSS and will ensure that Australian industry, the research community and the public can accurately align themselves and their data.
For more information on GDA2020, please visit the Australian Geospatial Reference System.