Esri Australia has been working with Esri and ICSM to ensure that the ArcGIS system can support clients migration from the GDA94 static datum to GDA2020 static datum. The ArcGIS system now fully supports data transformations via 7-parameter similarity transformation, or NTv2.0 transformation Grids.
As a result we are now seeing many clients migrate their authoritative datasets to GDA2020 and requiring all delivered data is in this same static datum. State and national governments are now delivering foundational open datasets in GDA2020 as well
In parallel to this migration we are also seeing more clients taking up WebGIS and delivering data via web services instead of shipping datasets or producing PDF’s. This is enabling a greater uptake web and mobile GIS, providing better informed field operators and getting live data in the hands of people who need it as they need it.
These two waves of change have presented a significant challenge. While transformations existed between WGS84 & GDA94 and GDA94 & GDA2020, there existed no direct path from GDA2020 to WGS84. If you wanted to place GDA2020 data into WebGIS you had to transform you data back through GDA94 to WGS84. Effectively moving the data back to its old location prior to publishing. Many clients asked why????
It has been termed the WGS84 Projection dilemma. So what’s changing?
In ArcGIS Online Map Viewer, all layers in a web map inherit the coordinate system of the basemap. WGS 1984 Web Mercator (auxiliary sphere) is the spatial reference of basemap services in the default Esri basemap gallery, meaning this is the default web GIS coordinate system. Layers also have their own spatial reference and transformations defined at a service level. When you add layers to the Web Map Viewer, an on-the-fly reprojection is performed to align your data with the coordinate system of the basemap.
When publishing data to web GIS you need to consider what spatial reference will be used to store the data at a service level, how the publishing process may affect it, as well as what transformations (or lack of) will be applied when the layer is displayed in a web map with a datum.
It is also important to understand GDA2020 and its relationship with web GIS. The de facto WGS84 in web GIS brings some challenges not unique to Australia or ArcGIS. Failing to address these challenges may result in data misalignment.
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.
GIS data must accurately represent real-world locations to be useful. To do this, you need a standard framework for defining location – a coordinate system. All spatial data utilises a coordinate system to position itself relative to your map and other data. However, coordinate systems are frameworks. They are models, spheroids, imperfect approximations of the shape of the Earth with all its bumps and curves as it changes with time. When working with spatial data you need to consider how a GIS positions this data against reality using coordinate systems.
By better understanding coordinate systems, you will be able to manage your data in a way that increases the accuracy of your maps and the work that you do with them. This blog is the first in a series taking a closer look at using Australian spatial references in ArcGIS. We will start by looking at geographic coordinate systems, projections, and transformations.
Esri recently released an update for the ArcGIS 10.2.1 for Utilities and Telecom that has included support for GDA2020 projections and transformations.
The update includes
- support for the mathematical transformation between GDA94 and GDA2020
- Support for the NtV2.0 Grid file transformations
- Also included are the Conformal and Conform + Distortion grid files.
If you intend on migrating to GDA2020 at 10.2.1 then we recommend you update to the latest Patch #9 available from
NOTE: this was first published Dec 2018 and has been amended in June 2021 to reflect additional software and transformation updates. See note at end of blog.
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.
With the delivery of ArcGIS Pro 2.2 and ArcGIS 10.6.1 Esri now supports GDA2020 NTv2 grid files out of the box. However, they are not installed with the product. We have had several reports now of customers deploying the latest product and the NTv2 transformations not being available.
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
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.
NOTE: This article refers specifically to ArcGIS 10.6 and ArcGIS Pro 2.1. For later versions of software please install the ArcGIS_Coordinate_Systems_Data_Windows software available from My.Esri to obtain the latest NTv2 files.
In 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.