The Geocentric Datum of Australia 2020 (GDA2020) has been the required operational mapping datum for activities carried out under the Petroleum and Geothermal Energy Act since August 2019. It replaced the earlier Geocentric Datum of Australia 1994 (GDA94) in order to correct for the ongoing movement of the tectonic plate on which Australia sits. Unless otherwise agreed in advance with the Department, all petroleum-related location surveying must be carried out in GDA2020 and Eastings and Northings must use the relevant Map Grid of Australia 2020 (MGA2020) Zone.
There is no requirement for any data that has already been supplied to DEM-ERD to be re-submitted in GDA2020 co-ordinates.
Following the transition to GDA2020, all new licence boundaries will be described in GDA2020, whilst historical boundaries will be preserved in their original datum. This is the same philosophy as was adopted during the transition to GDA94
ERD will transform selected key pre-existing datasets from GDA94 to GDA2020 co-ordinates. This will generally be done using the basic seven-parameter transformation (i.e. a distortion grid will not be applied). Other datasets will remain in GDA94 due to the practical constraints of updating the significant volume of data held by ERD. These data can still be loaded into most software correctly by specifying that it uses GDA94 co-ordinates.
For any assistance or guidance with GDA2020, please contact DEM.petroleum@sa.gov.au
Background information on GDA2020
The co-ordinates of physical locations in Australia (such as wells, seismic lines, pipelines etc.) are currently defined using the Geocentric Datum of Australia 1994 or “GDA94”. However, Australia sits on one of the Earth’s fastest moving tectonic plates, and by 2020, there will be an error of approximately 1.8m between a location’s GDA94 co-ordinates and its co-ordinates from global satellite positioning systems. This is because Australia’s GDA94 datum is plate-fixed and moves with the Australian continent whereas GPS co-ordinates are fixed to the centre of the earth.
To bring Australia’s coordinates into line with those from global satellite positioning systems, Australia will soon be changing to a new official national datum called the Geocentric Datum of Australia 2020 or “GDA2020”. The change will affect all users of location-based data.
The transition to GDA2020 is being facilitated by the Intergovernmental Committee on Surveying and Mapping (ICSM) and Geoscience Australia. For further information, we recommend the following useful links to their websites:
AHD elevations when converting between GDA94 and GDA2020
Heights such as Ground Level Elevations and Kelly Bushing Elevations etc. for petroleum-related data are usually stated with reference to the Australian Height Datum (AHD). AHD is the official national height reference datum for Australia and was adopted in 1971. It is based on mean sea level (MSL) observations at various mainland tide gauges around Australia. AHD has not been modified during the transition from GDA94 to GDA2020, hence heights such as the GL elevation or KB elevation for a well (referenced to AHD) will be the same in both GDA94 and GDA2020.
Confusion sometimes arises because GDA94 and GDA2020 are based on different realisations of the International Terrestrial Reference Frame and hence, for any given point, the height measured above the ellipsoid will vary by approximately 9cm between GDA94 and GDA2020. However, when an ellipsoidal height is converted to an AHD height (which has not changed during the transition from GDA94 to GDA2020), different geoid models must be used and these back out the effect of the change in the ellipsoid. The AUSGeoid09 model must be used when dealing with GDA94 co-ordinates and GDA94 ellipsoidal heights while the AUSGeoid2020 model must be used when using GDA2020 co-ordinates and GDA2020 ellipsoidal heights.
More information can be found on Geoscience Australia’s Australian Height Datum and Geoid Models webpage.
