Tag Archives: GDA2020

Understanding GDA2020 and it’s relationship with Web GIS


Australia sits on one of the Earth’s fastest moving tectonic plates which has been moving 70 millimetres per year. By 2020, Australia will have moved 1.8 metres north east of it’s location in 1994. To effectively map the earth, representations, known as datums are used to model and identify locations. Australia’s national datum; Geocentric Datum of Australia 1994 (GDA94) will soon be replaced by a new datum Geodetic Datum of Australia (GDA2020). GDA2020 will align with current positioning technology.

Geoscience Australia and the Intergovernmental Committee on Surveying and Mapping (ICSM) have released a new Geodetic datum GDA2020. The datum provides higher positional accuracy and will be able to represent locations dynamically rather than the stationary GDA94. .

In the coming two to three years most organisations will be transforming their spatial data from the GDA94 datum to the new GDA2020 datum. Esri’s, ArcGIS Software has been updated to accommodate these new datums across Australia and will support all of our customers rigorous requirements for locational and positional accuracy.

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GDA94, GDA2020 and WGS84; The projection dilemma

Progress supporting GDA2020:

The Intergovernmental Committee on Surveying and Mapping (ICSM) & Geoscience Australia (GA) recently released the definitions for the GDA2020 datum and associated projected coordinate systems covering Australia and its territories. Esri Australia has been working closely with ICSM & GA to ensure that ArcGIS software products support the new definitions.  Version 10.6 of ArcGIS and version 2.1 of ArcGIS Pro both include support for the new datum and projected coordinate systems (you can learn more in the Esri Australia Technical Blog)

Avoiding alignment issues mixing datums:

Web GIS, by default, displays data in the projection WGS84 Web Mercator (auxiliary sphere). When mapping data is shared to ‘Web GIS’, data is automatically reprojected ‘on-the-fly’ to this web projection in order to align with the displayed basemap and fit with the global projection. Most users do not realise that their data is being reprojected and in many instances occurs without issue.

However, while organisations are migrating to GDA2020 from GDA94 and using mixed data containing both datums, these mixed data sources will create a challenge when displayed in WGS84. The issue occurs when data is reprojected to the WGS84 Web Mercator projection.   Continue reading

GDA2020 & ArcGIS

It is now official on the 15th of December 2017 Geoscience Australia and the Intergovernmental Committee on Survey and Mapping (ICSM) launched the new GDA2020 datum.

In support of the new Australian datum, the following tools and resources have also been released by Geoscience Australia and ICSM:

So what does this mean for the ArcGIS product suite? Well from ArcGIS Pro 2.1 and ArcGIS 10.6 onwards all state, territory and national projections that incorporate the GDA2020 datum are supported.

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GDA2020 Transformations & ArcGIS

GDA2020 logo - text under symbolIn my previous articles on GDA2020 I have highlighted some of the considerations that organisations need to have when migrating to the new datum and reasons why Australia is deploying a new datum. These I hope have at least prepared you for what’s about to come.

In March Geoscience Australia released an interim paper (http://www.icsm.gov.au/gda2020/InterimReleaseNoteV1.0.pdf) regarding the definition of GDA2020 and its relationships to GDA94 and the International Terrestrial Reference Frame 2014 (ITRF2014) using similarity transformations. This provided the foundation for including the new datum into the Esri suite of products.

Shortly Geoscience Australia will release the full definitions for the GDA2020 datum and the NTv2.0 high resolution grid files for the accurate transformations from GDA94 to GDA2020. In preparation for this Esri Australia, Esri and Geoscience Australia have been working together to have the definitions and transformations available in the ArcGIS software suite. Esri is due to release an update for their ArcGIS 10.5.1 and ArcGIS Pro 2.0 suite of products. We anticipate this to be available mid to late June. These will be the first Esri products to include the GDA2020 definitions and transformations.
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Planning your move to GDA2020

In my last discussion I introduced the topic of the new GDA2020 datum, the reasons behind it and how Esri intends to implement support for this new geodetic datum. Now that the impending initial release of the first set of parameters is due shortly and with the NTv2 grid due before the end of the year, I thought it important, that as an organisation, it is time consider how do you go about planning the move to this new datum.
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