Alena Moison, Department of Environment, Land, Water and Planning

05/08/2016

GDA2020 – a modern datum for

Australia

Recent news

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ABC News Online, Thursday 28th July 2016

GDA2020 specifications

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• Conventional static datum like GDA94 but with rigorous uncertainty

• Just like GDA94, i.e. based on ITRF and fixed at a specific epoch:

- GDA94 = ITRF1992 @ 1994.0

- GDA2020 = ITRF2014 @ 2020.0

• Available from 1 January 2017

• Widespread implementation across Victoria expected in 2018

• Horizontal shift of approximately 1.6 m NE compared to GDA94

• Vertical drop of 0.09 m compared to GDA94

GDA2020 is our NEW geocentric datum

Historical datum changes

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Importance of datum

Enables integration of different datasets – measure once, use multiple times

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Why GDA2020?

Drivers to adopt a modernised geodetic datum for Australia:

• Crustal dynamics and regional deformation

• Significant technological developments

• Widespread distortions in GDA94

• GDA94 failing to support increasing accuracy needs of users

• International Terrestrial Reference Frame (ITRF) basis of all absolute

positioning technologies

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Crustal dynamics

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Australia sits on the fastest moving continental tectonic plate on Earth, in a

range of about 5 – 6 mm per month:

• Karratha: 70 mm/year

• Alice Springs: 67 mm/year

• Canberra: 58 mm/year

Infrastructure development

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+ AuScope GNSS Stations + AuScope + States StationsBefore AuScope

Infrastructure development

Automated datum maintenance

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GNSS technology

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• Capitalise on Australian investment

• Leverage international development in

multi-GNSS

• Leverage (user) GNSS device capability

Ubiquitous, accurate GNSS-assisted positioning in real time is inevitable

Centimetre positioning via smartphones is almost here

Intelligent transport: positioning relative to precisely mapped features requires

a reference frame aligned with ITRF

Source: http://gpsworld.com/accuracy-in-the-palm-of-your-hand

Positioning user capability

Two stage implementation

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Stage 1 - Geocentric Datum of Australia 2020 (GDA2020)

• Initial release available from 1 January 2017

• Conventional plate-fixed datum with rigorous uncertainty

• Based on latest ITRF2014, fixed at 1 January 2020

- From 2017 - 2023, offset from ITRF will reduce from 0.21m to zero &

back up to 0.21m

• Horizontal shift from GDA94 to GDA2020 will be approximately 1.6 metres

• Vertical offset between GDA94 and GDA2020 ellipsoidal heights will be

approximately 0.1 metres

• Projections - MGA2020 (UTM), VICGRID (conformal conic)

• AUSGeoid2020 will be released for use with GDA2020, AUSGeoid09 will

still need to be used with GDA94.

GDA94 to GDA2020 shift

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1.60m

1.49m

Two stage implementation

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Stage 2 - Australian Terrestrial Reference Frame (ATRF)

• Initial release commencing 1 January 2020

• Reference frame that caters for a dynamic Earth

• Aligned with ITRF, the location framework in use by the vast majority of

stakeholders

• Full deformation modelling capability

• Will require supporting standards & the adoption of tools in COTS

software before widespread adoption is realistic

• The future of AHD will be examined

Plate-fixed GDA2020 will be maintained until no longer needed

Datum modernisation roadmap

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1990 2000 2010 2020

GDA94 ATRF

(Continuously realised)

2017

GDA2020

User Implementation

Parameters, grid files and tools

Official transformation parameters and tools to convert between GDA94 and

GDA2020 and vice-versa:

• 7 parameter (Frame) transformation

• A 2D transformation and distortion grid file in the widely used Canadian

National Transformations version 2 (NTv2) format

• A 3D transformation grid file – HDF5 proposed (open source)

• Plate motion model (Euler parameters)

Values for the 14 parameter transformation supporting conversion of datasets

between GDA2020 and ITRF2014 will also be published.

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Transformation parameters

Parameters calculated from:

• Published GDA94 coordinates for defining 21 GNSS stations

• ITRF2014 coordinates at same stations

• Projected (from 2014) to 2020 using ITRF2014 velocity model

7 parameter transformation values (available October 2016)

• 3 shifts in origin (∆x,∆y,∆z)

• 3 rotations of axes (Rx,Ry,Rz)

• 1 change of scale (Sc)

Transformation is conformal

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Transformation grid file

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Allows for state-specific distortion component

• 2D and 3D

Formats

• 2D NTv2 (like AGD66/84 to GDA94)

• 2D ASCII text (for import to software)

• 3D - HDF5

Still some work to do to accommodate

state-specific distortion

Parent Grid

Sub Grid 1

Sub Grid 2

AHD remains unchanged

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AUSGeoid 2020

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Application

• To convert GNSS heights to AHD

heights

Major change from AUSGeoid09

• 9cm change in ellipsoidal

heights across Australia

Additions and improvements

• Improved gravity modelling

• Higher resolution (more data)

• Uncertainty

• Mean Sea Level model offshore

• Better in rugged terrain

AUSGeoid2020 will be released for use with GDA2020

AUSGeoid09 will still need to be used with GDA94

Transformation support

Online transformation tools and Web services

- Upload data (point or file)

Updated transformation software (GDAy)

Hardware devices to support collection of data in GDA2020 and GDA94

Provision of EPSG codes expected by 1st January 2017.

Adoption of parameters and grid within vendor software.

- GIS, Surveying, Engineering, FME

GDA2020 Technical Manual

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Next steps

• Data Audit

• Systems audit

• Educate stakeholders and suppliers

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Data audit

• Identify critical spatial data

• Including spatially referenced asset data

• Identify datasets to be transformed

• Critical dependencies

• Low accuracy/low resolution/high scale datasets may not require

transformation

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System audit

• Identify spatial data management systems are

in use:

- Software and versions

- Potential for upgrades

- Data stored in Excel spreadsheets?

• Watch for custom built applications, no longer

supported software/applications, applications

that don’t cater for spatial metadata (e.g.

datum, epoch)

• Users encouraged to contact vendors to

determine GDA2020 support

• Notify GDA2020 implementation working group

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Education

• Know your metadata (datum and epoch)!

• Ensure data providers are aware of your requirements and

when you plan to adopt GDA2020

• Ensure data users are aware of GDA2020 and issues that may

arise

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Alena Moison, Department of Environment, Land, Water and Planning

05/08/2016 27

GDA2020 – a new, modern datum for

Australia

Register @ www.gda2020.vic.gov.au