GDA2020 is replacing GDA94 and those using geographic data should start to think about the impact that this might have on their operations

Why Do We Need a New Datum?

Satellite-based global positioning systems (GPS) use a reference system fixed to the centre of the earth while our national systems are tied to known reference points on the Australian continent. In Australia the national datum GDA94 has been in use since 2000 and most coordinates (latitude and longitude or Map Grid of Australia) use this datum.

However since 2000, due to tectonic plate movement Australia has shifted so that the coordinates obtained by GPS are now different from those shown on maps using the GDA94 datum. The difference is expected to be about 1.8 metres by 2020 (1.6m in Victoria). While this may not seem a lot, in a world increasingly dependent on the precise location services offered by GPS such as precision agriculture, automated engineering technologies, drone-based deliveries, driverless vehicles etc, it is important that Australia’s datum is updated to align to global positioning systems.

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Approximate shift from GDA94 to GDA2020.

Approximate shift from GDA94 to GDA2020. (Source: ICSM

How Will It Affect Me?

It will depend on how you are using geographic data. If you are a water corporation with your asset data maintained in GDA94 your data will continue to remain in the same relative position while this data is maintained in GDA94. So if you know that pit X is precisely 4.567m from pit Y then it will remain 4.567 m after the datum has shifted. The GDA94 coordinates of the pits will not change over time.

However, if you are relying solely on GPS coordinates to locate pit X or Y this may be become more difficult in the future since without a local datum-based adjustment (i.e GDA94) in the GPS unit you are using, the values returned by the GPS will not match the coordinates of your data held in GDA94. The changes will largely affect those working with highly accurate GPS technology.

If you are using maps as part of your work, using car based GPS, maps which show the relative location of assets without referring to ‘absolute’ position you will not really notice any difference for the foreseeable future. Most state mapping data is not accurate enough for a 1.8 m shift to be detectable.

Modernising Australia's Datum (Source: ICSM)


  • Based on the International Terrestrial Reference Frame (ITFF). The ITRF is the basis of all absolute positioning technologies
  • Horizontal shift to approximately 1.8m NE across Australia compared to GDA94
  • Horizontal shift approximately 1.6m NE in Victoria 
  • Vertical drop of 0.09m compared to GDA94


  • GDA2020 became available from October 2017
  • In Victoria, DELWP will publish ‘dual streams’ of data in the second half of 2018. Master datasets will be maintained in GDA94 and transformed into GDA2020.
  • It will be widely implemented in Victoria in 2019


(Source: ICSM)

How Spatial Vision Can Help You

Data Audits

  • Know your data, know your datum.
  • Identify critical spatial data – what needs to be maintained?  
  • What are the priorities for data to be transformed into GDA2020?
  • What are the dependencies? 
  • Does your data have metadata which reflect the datum?

Systems Audits

  • Are your systems GDA2020 ready?  
  • Will software be available to capture new data in GDA2020 and undertake coordinate transformations from GDA94 to GDA2020?
  • Is critical data stored as coordinates in spreadsheets? 
  • What are your options for making your systems GDA2020 ready?

Educating Stakeholders

  • Train and inform staff about the proposed changes and the importance of maintaining good metadata
  • Data providers aware of client’s requirements for data in GDA2020
  • Ensure that data users understand the impact of the change 

What You Need To Be Ready For GDA2020

• Stay informed
     o Official Website:
     o Fact Sheets:
     o Victorian GDA2020 Newsletter:

• Be aware of how the changes may affect the management of your assets.

• If you are using Vicmap data, begin to download data in GDA2020 to see what impact it has on your own asset data.

• Make sure you are publishing and maintaing metadata. Make sure that you are maintaining information about the Datum of any information that you are providing to users including contractors. It is important that your contractors are aware of the impact of the transformation as while a difference of 1.8 metres may be trivial for most daily activities, if you are digging in the wrong place the results could be disastrous.

• If you’re using paper maps in GDA94 don’t worry. If data is accurate to no better than 3 metres (i.e paper maps) it is OK to say that the product is “GDA Compliant”.

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