Datum Modernisation in Australia

Nothing on the surface of the Earth is fixed. The Earth's tectonic plates are constantly moving in different directions and at different speeds. The Australian plate is moving in a north-easterly direction at a rate of about 7 cm per year.

This movement means that the latitude and longitude of points in Australia are changing. Since the implementation of the previous Australian datum, the Geocentric Datum of Australia 1994 (GDA94), the Australian plate has moved approximately 1.6 m, and Australia's coordinates are no longer aligned with Global Navigation Satellite Systems (GNSS) such as GPS. Differences of this magnitude are significant when it comes to applications that rely on accurate satellite positioning such as in-vehicle navigation, automated mining operations, precision agriculture and surveying where high absolute accuracies are required. To address this, Australia has implemented a new datum known as the Geocentric Datum of Australia 2020 (GDA2020).

The Intergovernmental Committee on Surveying and Mapping (ICSM) is responsible for modernising Australia's datum to ensure that all Australians can take advantage of the increased accuracy that current and future positioning and navigation technologies provide.

Geoscience Australia is the peak science agency responsible for technical development and maintenance of the national geodetic datum. Geoscience Australia has worked with each of the state and territory governments to update the coordinates of reference points that define GDA2020. Geoscience Australia will also be assisting Australian Government agencies and spatial software providers to adopt the new datum.

Transitioning to GDA2020

Due to the significant growth in the number of users of precise positioning and the expected improvement in positioning technology over the coming decade, Australia has started modernising its datum.

Australia's datum will be modernised in a two-stage approach to ensure that Australians continue to have access to the most accurate location information.

Stage 1: GDA2020 (available now)

The first stage is underway with the transition to the GDA2020. GDA2020 is the projected position of the Australian continent in 2020. Like GDA94, this datum is fixed to the Australian continent, where coordinates do not change with time. As a consequence, coordinates from GNSS such as GPS, will be offset by approximately 20 cm from GDA2020 in 2017; however, these coordinates will converge by 2020.

Stage 2: Australian Terrestrial Reference Frame (starting in 2020)

The second stage will commence in January 2020, when users will be able to transition to a time-dependent reference frame, that is, a datum/reference frame in which coordinates will change with time. This datum will be called the Australian Terrestrial Reference Frame (ATRF) and will provide the Australian community with a sustainable, traceable, high-precision geodetic reference system capable of meeting the most demanding positioning requirements. This datum will be fixed to the earth and will model the locations of reference points and their movement over time by maintaining full alignment to the International Terrestrial Reference Frame (ITRF).

NOTE: GDA2020 will still be available for users who do not need a time-dependent reference frame.

To support the transition of spatial software providers and Australian Government agencies to GDA2020, the Intergovernmental Committee on Surveying and Mapping (ICSM) and Geoscience Australia have developed a range of products, tools and technical resources which are available below:

Transformation Grids

The difference between GDA94 and GDA2020 coordinates includes a conformal transformation component, primarily due to plate tectonic motion (Figure 1), and an irregular (non-conformal) distortion component. The conformal component accounts for the primary coordinate movement between GDA94 and GDA2020, and replicates a seven-parameter similarity transformation.

Map of Australia with green lines pointing in a northeast direction indicating the plate tectonic motion of the Australian continent as observed at Global Navigation Satellite System sites

Figure 1: The difference between GDA94 and GDA2020 coordinates is primarily due to tectonic plate motion.

The distortion component is attributable to several second-order effects, such as:

  • an improved realisation of the global reference frame over time
  • irregular ground movement since GDA94 was established
  • improvements in computation methods since GDA94.

These effects vary in magnitude and direction around the country and can be as large as ~0.5 m.

Two grids have been developed to assist with the implementation of GDA2020.

The GDA94 - GDA2020 Online Transformation Service is now available.

Conformal grid:

Predominantly plate tectonic motion (~1.7 m NNE) and replicates a seven-parameter similarity transformation. GDA94-GDA2020 Conformal grid is available here.

NOTE: If GDA94 coordinates were observed using Global Navigation Satellite System (GNSS) technology, with corrections coming from a network of GNSS reference stations (such as GPSnet, CORSnet-NSW), it is likely that the coordinates will be unaffected by local distortions. In this case, the Conformal grid or a seven-parameter similarity transformation would be most suitable to transform the GDA94 coordinates to GDA2020.

Conformal and Distortion grid:

Includes regional distortion caused by second-order effects described above. GDA94-GDA2020 Conformal and Distortion grid is available here.

NOTE: If survey control marks were used for referencing and establishing GDA94 coordinates, localised distortion would need to be taken into account. In this case, the Conformal and Distortion grid should be used to transform to GDA2020 coordinates. If in doubt, contact your state or territory land survey authority.

GDA94 to GDA2020 online transformation service

Geoscience Australia has developed a web service powered by Feature Manipulation Engine (FME) that will transform selected spatial format files from GDA94 to GDA2020 using the Transformation Grids. Users will be able to simply 'drag and drop' files onto the page and receive an email with a link to download the output file.

The web service is a reference standard that enables software developers and spatial professionals to transform their data online.

This service is not intended to enable users to transform all their data from GDA94 to GDA2020; instead, it aims to provide a method of checking systems and processes implemented by the government or the spatial industry to ensure the transformation results are correct.

The online transformation service accepts Shapefiles, CSV, ASCII, GeoTiff, ECW, Jpeg2000 and GeoJSON files.

Software and plugins

ICSM provides many other software tools and plugins (including QGIS). For more information, please refer to the ICSM Transformation products and tools.

GDA2020 Technical Manual

The ICSM GDA2020 Technical Manual defines and describes the preferred methods to transform coordinates between GDA94 and GDA2020, and other historical Australian datums. Furthermore, it provides information on how to perform coordinate conversions and apply the appropriate AUSGeoid model when converting between ellipsoidal heights and AHD heights.

AUSPOS

AUSPOS is a free online GPS data processing facility provided by Geoscience Australia. AUSPOS allows users to upload their dual frequency geodetic quality GPS RINEX data observed in a 'static' mode and provides an AUSPOS report via email (often in less than five minutes) GDA2020, GDA94 and ITRF2014 coordinates.

More information on AUSPOS is available from the Geoscience Australia website.

AUSGeoid2020

AUSGeoid2020 is a model of the offset between the ellipsoid (GDA2020) and the Australian Height Datum. For the first time, the AUSGeoid2020 model also provides location-specific uncertainty values along with the result.

More information is available from the Geoscience Australia website.

Coordinate transformation and conversion tools

Geoscience Australia and ICSM have developed a range of tools to assist with coordinate transformation and conversions.

More information is available via the Geoscience Australia website.

Fact sheets

ICSM has developed a range of fact sheets to assist with the implementation of GDA2020.

These fact sheets are available from the ICSM website.

Australian Government agencies that generate or manage spatial information will need to implement changes to adjust to GDA2020. Geoscience Australia can help agencies to ensure seamless implementation of the new datum with minimal disruption to existing systems and processes.

Transitioning to GDA2020 is not mandatory; however, Australian Government agencies are strongly encouraged to transition their spatial data as early as possible. This transition will ensure datasets are consistent across government and are compatible with current and future positioning and navigation technologies. The initial impact of the datum change will be most significant for existing spatial datasets and precise positioning systems with coordinate uncertainties of less than three metres. For further information contact Geoscience Australia on clientservices@ga.gov.au.

Geospatial software providers are strongly encouraged to adopt GDA2020 as early as possible. Early adoption by software providers will enable users to make the transition.

Geoscience Australia has developed a range of tools and services to support software providers to transition to the GDA2020. Please refer to the Products and Tools to assist with transition tab for more information.

Geoscience Australia has been working with the European Petroleum Survey Group (EPSG) of the International Association of Oil and Gas Producers to define the EPSG geodetic codes for GDA2020; these codes are available in the GDA2020 Technical Specifications tab.

The Australian Terrestrial Reference Frame (ATRF) will start being implemented for users in 2020. The ATRF realisations will be Earth-fixed and highly accurate to the International Terrestrial Reference Frame (ITRF) and WGS84 reference frame realisations utilised by GNSS. For further information or help in developing software to meet this emerging user need, contact Geoscience Australia on clientservices@ga.gov.au.

Datum:

Geocentric Datum of Australia 2020 (GDA2020)

Geographical coordinate set:
(latitude, longitude)

Geocentric Datum of Australia 2020 (GDA2020)

Grid coordinates:
(eastings, northings, zone)

(Universal Transverse Mercator, using the GRS80 ellipsoid)
Map Grid of Australia 2020 (MGA2020)

Reference Frame:

ITRF2014 (International Terrestrial Reference Frame 2014)

Ellipsoid:

GRS80

Semi-major axis (a):

6,378,137 metres

Inverse flattening (1/f):

298.257222101

Epoch:

2020.0

EPSG CRS code

EPSG name

Type

Area Description

1168

Geocentric Datum of Australia 2020

GeodeticDatum

Australia including Lord Howe Island, Macquarie Islands, Ashmore and Cartier Islands, Christmas Island, Cocos (Keeling) Islands, Norfolk Island. All onshore and offshore.

7842

GDA2020

GeodeticCRS (geocentric)

Australia including Lord Howe Island, Macquarie Islands, Ashmore and Cartier Islands, Christmas Island, Cocos (Keeling) Islands, Norfolk Island. All onshore and offshore.

7843

GDA2020

GeodeticCRS (geographic 3D)

Australia including Lord Howe Island, Macquarie Islands, Ashmore and Cartier Islands, Christmas Island, Cocos (Keeling) Islands, Norfolk Island. All onshore and offshore.

7844

GDA2020

GeodeticCRS (geographic 2D)

Australia including Lord Howe Island, Macquarie Islands, Ashmore and Cartier Islands, Christmas Island, Cocos (Keeling) Islands, Norfolk Island. All onshore and offshore.

7845

GDA2020 / GA LCC

ProjectedCRS

Australia - Australian Capital Territory; New South Wales; Northern Territory; Queensland; South Australia; Tasmania; Western Australia; Victoria.

7846

GDA2020 / MGA zone 46

ProjectedCRS

Cocos (Keeling) Islands - offshore west of 96°E.

7847

GDA2020 / MGA zone 47

ProjectedCRS

Cocos (Keeling) Islands - onshore and offshore east of 96°E.

7848

GDA2020 / MGA zone 48

ProjectedCRS

Australia - offshore west of 108°E. Christmas Island - onshore and offshore west of 108°E.

7849

GDA2020 / MGA zone 49

ProjectedCRS

Australia - onshore and offshore west of 114°E. Christmas Island - offshore east of 108°E.

7850

GDA2020 / MGA zone 50

ProjectedCRS

Australia - onshore and offshore between 114°E and 120°E.

7851

GDA2020 / MGA zone 51

ProjectedCRS

Australia - onshore and offshore between 120°E and 126°E.

7852

GDA2020 / MGA zone 52

ProjectedCRS

Australia - onshore and offshore between 126°E and 132°E.

7853

GDA2020 / MGA zone 53

ProjectedCRS

Australia - onshore and offshore between 132°E and 138°E.

7854

GDA2020 / MGA zone 54

ProjectedCRS

Australia - onshore and offshore between 138°E and 144°E.

7855

GDA2020 / MGA zone 55

ProjectedCRS

Australia - onshore and offshore between 144°E and 150°E.

7856

GDA2020 / MGA zone 56

ProjectedCRS

Australia - onshore and offshore between 150°E and 156°E.

7857

GDA2020 / MGA zone 57

ProjectedCRS

Australia including Lord Howe Island and Macquarie Islands - onshore and offshore between 156°E and 162°E.

7858

GDA2020 / MGA zone 58

ProjectedCRS

Australia - offshore east of 162°E. Norfolk Island - onshore and offshore west of 168°E.

7859

GDA2020 / MGA zone 59

ProjectedCRS

Norfolk Island - offshore east of 168°E.

7899

GDA2020 / Vicgrid

ProjectedCRS

Australia - Victoria.

8013

GDA2020 / ALB2020

ProjectedCRS

Australia - Western Australia - Albany area onshore below 190m AHD.

8014

GDA2020 / BIO2020

ProjectedCRS

Australia - Western Australia - Barrow Island and Onslow area onshore.

8015

GDA2020 / BRO2020

ProjectedCRS

Australia - Western Australia - Broome area onshore below 130m AHD.

8016

GDA2020 / BCG2020

ProjectedCRS

Australia - Western Australia - Busselton area onshore below 250m AHD.

8017

GDA2020 / CARN2020

ProjectedCRS

Australia - Western Australia - Carnarvon area onshore.

8018

GDA2020 / CIG2020

ProjectedCRS

Christmas Island - onshore.

8019

GDA2020 / CKIG2020

ProjectedCRS

Cocos (Keeling) Islands - onshore.

8020

GDA2020 / COL2020

ProjectedCRS

Australia - Western Australia - Collie area between 50m and 310m AHD.

8021

GDA2020 / ESP2020

ProjectedCRS

Australia - Western Australia - Esperance area onshore.

8022

GDA2020 / EXM2020

ProjectedCRS

Australia - Western Australia - Exmouth area onshore below 160m AHD.

8023

GDA2020 / GCG2020

ProjectedCRS

Australia - Western Australia - Geraldton area onshore below 195m AHD.

8024

GDA2020 / GOLD2020

ProjectedCRS

Australia - Western Australia - Kalgoorlie area.

8025

GDA2020 / JCG2020

ProjectedCRS

Australia - Western Australia - Jurien Bay area onshore below 200m AHD.

8026

GDA2020 / KALB2020

ProjectedCRS

Australia - Western Australia - Kalbarri area onshore.

8027

GDA2020 / KAR2020

ProjectedCRS

Australia - Western Australia - Karratha area onshore.

8028

GDA2020 / KUN2020

ProjectedCRS

Australia - Western Australia - Kununurra area onshore below 200m AHD.

8029

GDA2020 / LCG2020

ProjectedCRS

Australia - Western Australia - Lancelin area onshore below 200m AHD.

8030

GDA2020 / MRCG2020

ProjectedCRS

Australia - Western Australia - Margaret River area onshore below 200m AHD.

8031

GDA2020 / PCG2020

ProjectedCRS

Australia - Western Australia - Perth area onshore below 165m AHD.

8032

GDA2020 / PHG2020

ProjectedCRS

Australia - Western Australia - Port Hedland area onshore.

8058

GDA2020 / NSW Lambert

ProjectedCRS

Australia - New South Wales.

8059

GDA2020 / SA Lambert

ProjectedCRS

Australia - South Australia.

8048

GDA94 to GDA2020 (1)

Coordinate Transformation

Australia including Lord Howe Island, Macquarie Islands, Ashmore and Cartier Islands, Christmas Island, Cocos (Keeling) Islands, Norfolk Island. All onshore and offshore.

8049

ITRF2014 to GDA2020 (1)

Coordinate Transformation

Australia including Lord Howe Island, Macquarie Islands, Ashmore and Cartier Islands, Christmas Island, Cocos (Keeling) Islands, Norfolk Island. All onshore and offshore.

For more details on the EPSG Geodetic Parameter Registry, please see www.epsg.org.

If further assistance is required, please contact: geodesy@ga.gov.au.