The Geocentric Datum of Australia 2020 (GDA2020) is a geocentric (earth-centred) coordinate reference system that is Australia’s new official national datum. GDA2020 will eventually supersede the GDA94 datum and older coordinate systems, such as Australian Geodetic Datum 1966 and 1984 (AGD66 and AGD84).
It is a ‘plate-fixed’ datum that is aligned with the 2014 realisation of the International Terrestrial Reference Frame (or ITRF2014). The “earth-fixed” ITRF is typically not regarded as a “datum” — rather it is the international standard reference framework to which national geocentric datums are aligned.
GDA2020 coordinates differ from GDA94 coordinates by approximately 1.5 to 1.8 metres and are more closely aligned with the reference frameworks used by modern GNSS – such as GPS, GLONASS, Galileo and BeiDou.
GDA2020 is defined in the National Measurement (Recognized-Value Standard of Measurement of Position) Determination 2017 by the coordinates on 109 geodetic reference stations known as the Australian Fiducial Network (AFN). These coordinates are referenced to the International Terrestrial Reference Frame 2014 at epoch 2020.0. That is, on January 1 2020, ITRF2014 at epoch 2020.0 will coincide with GDA2020. From 2017 when GDA2020 is established until January 1 2020, the difference between ITRF2014 coordinates at the date of observation (called the observation epoch) and GDA2020 coordinates will continually converge as the Australian tectonic plate moves 7 cm per year in a north-easterly direction. From January 1 2020, there will be an increasing divergence between the coordinates on GDA2020 and ITRF2014.
The Recognized-Value Standard of Measurement of Position for GDA94 has been repealed.
GDA2020 coordinates can be accessed via spatial connection to the Australian geodetic reference stations with GDA2020 coordinates either:
- directly via linked GNSS measurements, or
- from other GNSS CORS stations with Regulation 13 Certification issued by Geoscience Australia, or
- via a traceable connection to geodetic survey control stations constrained to the AFN, or
- GDA94 coordinates may also be transformed to GDA2020 coordinates using the transformation products and tools published by ICSM.
The standard map projection associated with GDA2020 is the Map Grid of Australia 2020 (MGA2020), a transverse Mercator projection that conforms to the internationally standardised Universal Transverse Mercator Grid system.