Introduction of GDA2020 to ArcGIS and how to install additional transformations

Australia has recently moved towards a new datum, the Geocentric Datum of Australia 2020 (GDA2020), to facilitate a more robust, accurate and capable datum that is more closely aligned with the expectations of a modern, connected Australia.

The introduction of a new datum impacts all areas of the software. Esri support for GDA2020 was progressively added as the datum parameters and associated transformation methods were released. All current releases of ArcGIS Pro (2.2 onward) and ArcGIS Desktop (10.6.1 onward) now support GDA2020, the associated projections, and transformations between it and GDA94.

An additional installation is required to support the NTv2 grid-based transformation methods released for GDA94-GDA2020.

GDA94-GDA2020 transformations

As you move towards adopting GDA2020 there will be scenarios where you will need to work with data based on GDA94 and or GDA2020 datums. As these datums are different the same location on the ground will have different coordinate values. If you are working with both datums in one map, or, if you are looking to project your source data between the two, you will need to use a coordinate transformation.

Remember – projected coordinate systems will have an underlying datum!

A transformation is an operation that converts the coordinates of a point in one coordinate system to the coordinates of the same point in another coordinate system.  ArcGIS Pro includes a mathematical seven parameter similarity transformation between GDA2020 and GDA94 out of the box, with two additional grid-based transformation methods available as a separate installation through My Esri. Once installed there will be three transformation paths available:

  • GDA 1994 To GDA 2020 1*
  • GDA 1994 To GDA 2020 NTv2 3 Conformal**
  • GDA 1994 To GDA 2020 NTv2 2 Conformal and Distortion**

Transformation paths apply both to and from the specified coordinate systems.
*Seven parameter similarity transformation
**Additional grid-based transformation methods available through a separate installation. Some parts of the ArcGIS Platform will only support the transformation methods available by default.

A grid-based transformation method can be very accurate in modeling small changes between two geographic coordinate systems. Grid files can be reasonably large. The ICSM released two 2D national transformation grids as follows:

  • Conformal: A grid version of the seven parameter similarity transformation. The basic difference between GDA94 and GDA2020 coordinates primarily due to plate tectonic movement (approximately 1.8m NNE over 26 years); and
  • Conformal + Distortion: Incorporates the conformal seven parameter similarity transformation plus localised and regional distortion revealed by incorporating coordinates on the ground survey control networks across the nation.

Installing the grid-based transformation methods

Due to the size of the NTv2 grid-based transformation method, they are not included in the default software installation. They are available as a separate installation downloadable from My Esri:

My Esri > Downloads > Products > ArcGIS Pro (select version* and then view downloads) > Data and Content > ArcGIS Coordinate Systems Data

*It is important to select the correct version of ArcGIS software installed as there have been changes between each release, and early versions of ArcGIS Desktop do not support GDA2020.

If you don’t have access to downloading software through My Esri you can request permissions to download, reach out to your organisation’s IT or GIS administrators, or contact Technical Support.

Proceed through the installation wizard accepting all defaults until the Select Features step. Here you may change the installed features so that only the NTv2 method files are installed, saving disk space:

During ArcGIS Coordinate Systems Data Setup click the icons to only apply the files needed for GDA2020-GDA94 NTv2 methods

Silently installing the grid-based transformation methods

For scripted and automated installations or deployments you can call on the unpacked installation files with additional parameters, such as only selecting the NTv2 method files for install:

  1. In My Esri, download the ArcGIS Coordinate Systems data for the appropriate ArcGIS release.
  2. Run the downloaded .exe to unpack the installation files (choosing a folder as necessary).
  3. Run one of the following commands with the necessary user privileges and path amended to where the files were extracted in step 2:
  • For a silent install with no progress bar or confirmation and only NTv2 files:
    • <path_to_extracted_files>\CoordinateSystemsData\SetupFiles\CSD.msi  /qn ADDLOCAL="NTv2"
  • For a silent install with progress bar and simple GUI with no options or clicks:
    • <path_to_extracted_files>\CoordinateSystemsData\SetupFiles\CSD.msi  /passive ADDLOCAL="NTv2"

Support in earlier versions of ArcGIS

Esri support for GDA2020 was progressively added as the coordinate system and associated transformation methods were released. The versions of ArcGIS Pro and ArcMap discussed below are in mature or retired support. If you are on one of these versions, you should consider upgrading to a more recent release.

  • ArcGIS 10.5 and ArcGIS Pro 2.0 introduced the GDA2020 datum. It became visible under Coordinate Systems and allowed new data to be collected within this spatial reference. However, the transformation methods were not available at the time, and existing data could not be projected to GDA2020.
  • ArcGIS 10.6 and ArcGIS Pro 2.1 introduced the mathematical seven parameter similarity transformation. ICSM also developed two 2D national transformation grids for GDA94-GDA2020 that were not released with the software. They could be manually included by downloading the grid files, renaming them, and placing them into the appropriate product directory.
  • With ArcGIS 10.6.1 and ArcGIS Pro 2.2, Esri now includes GDA2020 as a coordinate system and supports GDA2020 NTv2 grid files through a separate ArcGIS Coordinate Systems Data installer.

Do not download and rename the grid files manually for recent ArcGIS releases.

GDA2020 is not supported in earlier versions of ArcGIS except for the ArcGIS 10.2.1 utility release.

Moving to GDA2020 and looking for a strategy built on a thorough analysis of your requirements? Find out more about Esri Australia GDA2020 service packages and book a free consultation here.

Continue reading:

  1. Understanding Spatial References in Australia
  2. The introduction of GDA2020 to ArcGIS and how to additional transformations (current page)
  3. Working with coordinate systems and transformations in ArcGIS Pro
  4. GDA2020, ArcGIS Online and the Web Mercator Dilemma

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