To bring Australia’s coordinates into line with those from global satellite positioning systems, Australia is changing to a new official national datum called the Geocentric Datum of Australia 2020 or “GDA2020”.
THIS CHANGE WILL AFFECT ALL USERS OF SPATIAL DATA.
The Department for Energy and Mining (DEM) transitioned its systems from GDA94 to GDA2020 and its associated Map Grid (MGA2020) over the weekend of 10th and 11th August 2019. From that point, and subject to the practical and pragmatic approach outlined below, GDA2020 will be the required operational datum for all South Australian petroleum-related activities.
To assist companies with the management of this transition, the Energy Resources Division (ERD) provides the following guidance:
- PREVIOUSLY-SUPPLIED DATA. There is no requirement for any data that has already been supplied to DEM-ERD to be re-submitted in GDA2020 co-ordinates.
- ONGOING AND IMMINENT DATA ACQUISITION. The data from any ongoing or imminent acquisition or processing projects using GDA94 co-ordinates should be submitted to DEM using that datum. After August 2019, the acquisition of any new petroleum-related data should be carried out in GDA2020 co-ordinates unless otherwise agreed with DEM-ERD.
- REGULATIONS AND GUIDELINES. The Petroleum and Geothermal Energy Regulations and associated Guidelines will be updated in due course to reflect that GDA2020 will be South Australia’s official mapping datum.
- LICENCE BOUNDARIES. 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
- CONVERSION OF EXISTING DATA HELD BY DEM-ERD. ERD will transform selected key 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.
- ASSISTANCE AND GUIDANCE: For any assistance or guidance during the transition to GDA2020, please contact email@example.com
- PRAGMATIC APPROACH DURING THE TRANSITION PERIOD. Notwithstanding the above, DEM-ERD will take a pragmatic approach to the future supply of co-ordinate data (for example, where a survey crosses into another jurisdiction that has not yet transitioned to GDA2020 as its official datum). In the event of any issues or problems, please contact ERD to discuss how to proceed.
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:
Clarification on elevation data referenced to AHD when converting between GDA94 and GDA2020
The following clarification is provided following several enquiries from industry
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.