GDA2020 South Australia Update August 2019

August 12, 2019

SA eNews #9  

ANZLIC – The Spatial Information Council has announced 30 June 2020 is the date by which ANZLIC member agencies in Australian states and territories will be ready to deliver and receive foundation spatial data on the GDA2020 Datum.

The South Australian Government agencies that provide spatial data continue to progress the implementation of GDA2020 and its associated Map Grid, MGA2020, to meet the ANZLIC adoption date.

GDA2020 logo

The GDA2020 logo is available for spatial data and application producers to identify products that are GDA2020 compliant, compatible, or capable of handling GDA2020 coordinates.

There are three logo styles offered.                   

Users of the logo must agree to the conditions of use on the Intergovernmental Committee on Surveying & Mapping (ICSM) GDA2020 logo webpage prior to downloading the files.

Free Webinars

The Australian Government has committed $225m to Geoscience Australia to provide 5-10 cm accurate positioning to anyone, anytime, anywhere in Australia by 2023. This is a significant improvement from the 5-10m accuracy that can currently be achieved using GPS enabled devices.  In anticipation for the growing use and reliance on positioning technology, the Intergovernmental Committee on Surveying and Mapping’s Permanent Committee on Geodesy (ICSM PCG) is leading the upgrade of a number of elements of Australia’s Geospatial Reference System (AGRS) to ensure Australian’s can maximise the benefits of precise positioning.

The Surveying & Spatial Sciences Institute (SSSI) and the ICSM PCG are jointly hosting a series of webinar on upgrades to the AGRS; the collection of datums, reference frames, models, infrastructure and standards needed for accurate 4D positioning.  The four part GDA2020 series is being presented by Nicholas Brown, Director of National Geodesy at Geoscience Australia.

The webinars are free of charge for SSSI members and non-members.

Part 1: Upgrading the Australian Geospatial Reference System

Wednesday 21 August | 12.00 - 1.00pm

Part 2: Geocentric Datum of Australia 2020

Monday 9 September | 12.00 - 1.00pm

Part 3: Australian Terrestrial Reference Frame

Monday 21 October | 12.00 - 1.00pm

Part 4: Height: Ellipsoid, geoid, Australian Height Datum and Australian Vertical Working Surface

Thursday 28 November | 12.00 - 1.00pm

More information and webinar registration

GNSS Continuously Operating Reference Stations (CORS)

The coordinates used to fix CORS base stations across Australia have been changed to GDA2020.

All streams from Geoscience Australia via AUSCORS now have GDA2020 mountpoints and SmartNet, AllDayRTK and VRSNow Australia provide GDA2020 and GDA94 coordinates for their services.

Users of GNSS CORS will need to ensure that GNSS receivers are set to the correct mountpoint for the service connecting to and for the datum to be used to reference coordinates; either to continue with GDA94 or switch to GDA2020.

Refer to the Using GDA2020 with CORS fact sheet and contact your CORS provider for further details.

Remember, when using GDA2020 ellipsoidal heights, the AUSGEIOD2020 model must be used to derive AHD heights; AUSGEIOD09 must still be used for GDA94 ellipsoidal heights.

Refer to Geoscience Australia’s AHD and Geoid models webpage for details.

Data.SA

Some agencies have released geospatial datasets in GDA2020 format through the South Australian Government Data Directory, Data.SA.

The datum for datasets will be apparent in the file name.  For example, zip files will contain files ending in “_GDA2020” or “_GDA94”.

GDA94 datasets will continue to be available from Data.SA until at least the end of year 2020. 

It is now imperative to note the metadata of any dataset to ensure you are using the appropriate datum or projection. “Know your data, know your datum

Web Mercator Dilemma

The June/July edition of the SSSI Position magazine published an article by Michael Giudici (Chair of GMIWG) relating to the ‘Web Mercator Dilemma’.  This so-called dilemma is a result of WGS84 historically becoming the default datum for web mapping.  Transformations between datums in a web mapping environment often includes transforming to WGS84 first and then to the target datum.  This was fine for GDA94 as in 1994 WGS84 could be considered equivalent to GDA94 and web mapping performs a ‘null transformation’.   GDA2020 to WGS84 (@ 1994) is not a ‘null transformation’, it is approximately 1.8m different, and whilst software can correctly transform between the new GDA2020 and GDA94 for desktop applications, once data is re-projected to a web environment, data transformed from GDA2020 will not align with data transformed from GDA94.  This has the potential to cause significant problems with display and analysis of datasets.  Esri Australia has a technical blog explaining the issue and suggested solutions.

ICSM has been working to introduce ‘work-arounds’, however a more definitive solution is being pursued.

For more information on GDA2020 including fact sheets and transformation tools visit the ICSM website.

Please direct any queries regarding the implementation of GDA2020 to me at bradley.slape@sa.gov.au.  The online GDA2020 Forum is also available for technical queries.

Bradley Slape

SA Member, ICSM GDA Modernisation Implementation Working Group (GMIWG)

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