transitioning to gda2020 the new geocentric datum of australia · the new geocentric datum of...
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Transitioning to GDA2020 The new Geocentric Datum of Australia
Roger Fraser
Office of Surveyor-General Victoria
2017 Vicmap Information Sessions
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Communication channels
• Animation �
• Factsheets
• Website: http://www.icsm.gov.au �
Modernising Australia’s Datum
• Register for Victorian e-newsletter:
http://gda2020.vic.gov.au
ICSM communications
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http://www.icsm.gov.au � Modernising Australia’s Datum � Online forum
ICSM communications
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Why GDA2020?
Drivers for a modernised geodetic datum for Australia
• Crustal dynamics and regional deformation
• Significant technological developments in underlying geodetic
infrastructure and user-community positioning devices
• Widespread distortions in GDA94
• GDA94 fails to support increasing accuracy needs of users
• All absolute positioning technologies based upon the
International Terrestrial Reference Frame (ITRF)
• Future mass market access to precise positioning
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Datum modernisation
• An ongoing and essential task for any country seeking to provide
accurate and reliable positioning for the community
Historical datum changes
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GDA2020 specifications and implementation
Two stage approach
Stage 1 – Geocentric Datum of Australia (GDA2020)
• Conventional static datum like GDA94 with rigorous uncertainty
• Just like GDA94 — based on ITRF, fixed at a specific epoch:
- GDA94 = ITRF1992 @ 1994.0
- GDA2020 = ITRF2014 @ 2020.0
• Horizontal shift of approx. 1.6 m NE from GDA94, with slight rotation
• Consistent vertical drop of 0.09 m from GDA94
• Available for adoption from mid February 2017
• Projections: MGA2020 (UTM), VICGRID (conformal conic)
• AUSGeoid2020 will be released with GDA2020
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GDA2020 specifications and implementation
Two stage approach
Stage 2 - Australian Terrestrial Reference Frame (ATRF)
• Initial release commencing January 2020
• Reference frame that caters for a dynamic Earth
• Aligned with ITRF, the reference frame in use by satellite positioning
• Will require supporting standards & the adoption of tools in major software
before widespread adoption is realistic
• Modernisation of AHD will be investigated
Plate-fixed GDA2020 (Stage 1) will be maintained until no longer needed
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GDA94
implementation
GDA2020 specifications and implementation
1994 2000 2017 2020 2023
@ 2000 @ 2017 @ 2020 @ 2023
-0.42m +0.21m -0.21m
@ 1994
GDA94 GDA2020
GNSS
+1.6m
GDA2020
implementation ATRF
implementation
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1mm
GDA94 to GDA2020 shift
1.60m
1.49m
Consistent 0.09m drop in ellipsoid height
1.58m
1.54m
1.52m1.56m1.58m
1.59m
1.57m 1.53m
1.55m
MGA94 MGA2020
MGA94
MGA94
MGA2020
MGA2020
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Next steps
Preparing for transition
1. Data audit
2. Systems audit
3. Educate stakeholders and suppliers
Source and lineage
Metadata
Awareness and
education
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Next steps
Data audit
• Identify critical spatial data
• Ensure critical data is tagged with correct Coordinate Reference System
• Identify what datasets need to be transformed, when they should be
transformed and critical dependencies
• Low accuracy or low resolution datasets may not require transformation
• Beware of WGS84!
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WGS84 – what is it aligned to now?
WGS84 is not what it seems
• WGS is the global reference frame that GPS is based upon.
• What is it aligned to?
WGS84 – original realisation completed in 1987
WGS84 (G730) – aligned with ITRF 1991 @ 1991.0
• Adopted Jan 1994
WGS84 (G873) – aligned with ITRF 1994 @ 1994.0
• Adopted Sep 1996
WGS84 (G1150) – aligned with ITRF 2000 @ 2001.0
• Adopted Jan 2002
WGS84 (G1674) – aligned with ITRF 2008 @ 2005.0
• Adopted in Feb 2012
WGS84 (G1762) – aligned with ITRF 2008 @ 2005.0 (no change)
• Adopted in Oct 2013
WGS84 (G…) – aligned with ITRF ???? @ ????
• Adoption ?
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IGS – what is it aligned to now?
What is post-processed GNSS aligned to?
• Post-processing requires precise orbits of GNSS satellites (from IGS)
• Precise orbit products aligned to different ITRF versions
Source: http://acc.igs.org/igs-frames.html
IGS = International GNSS Service (see http://igs.org)
ITRF 1992 02.01.1994 31.12.1994
ITRF 1993 01.01.1995 29.06.1996
ITRF 1994 30.06.1996 01.12.2001
ITRF 2000 02.12.2001 04.11.2006
ITRF 2005 05.11.2006 16.04.2011
ITRF 2008 17.04.2011 29.01.2017
ITRF 2014 29.01.2017 …
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Next steps
Systems audit
• Field equipment firmware support?
• Identify GIS and data management systems:
- On-the-fly transformation capability?
- Version and potential for upgrades?
• Data in proprietary/text files on shared drives,
database, or Web service (WMS/WMTS)?
• Watch out for custom built applications,
unsupported software/applications, or
legacy apps that ignore spatial metadata
• Is transition dependent on system capability?
• Users encouraged to contact software vendors
to determine GDA2020 support
• For any issues, post to GDA2020 Online Forum
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Next steps
Educate stakeholders and suppliers
• Know your metadata – datum, epoch, lineage, uncertainty
• Understand what datum data is captured in
• 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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Data, parameters, software and support
DELWP transition
• DELWP Implementation Plan developed
• System upgrades already commenced
• Dual support progressively available
from 3rd quarter 2017
• SMES (dual coordinates, sketch plans/reports,
Web services)
• GPSnet (dual GDA94/GDA2020 streams)
• Vicmap, Spatial Datamart (dual WMS/WMTS)
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Data, parameters, software and support
Parameters and grid files
• Official transformation parameters are available to convert
between GDA94 and GDA2020 and vice-versa
• 7 transformation parameters
• Plate motion model (Euler parameters)
• Also, 14 transformation parameters
(7 parameters + 7 rates of change) supporting:
• GDA2020 ↔ ITRF2014 and
• GDA2020 ↔ previous ITRFs (e.g. ITRF2008, ITRF2005, …)
Under development
• A 2D transformation grid file in the widely-used NTv2 format
• A 3D transformation grid file – HDF5 proposed (open source)
GDA94 GDA2020MGA94 GDA94 GDA2020Projection Geographic Cartesian Cartesian Geographic Projection
E, N, zone Lat, Long, height X, Y, Z X, Y, Z Lat, Long, height E, N, zone
MGA2020Transformation
by 7 params or grid
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Data, parameters, software and support
Software, tools, documentation and examples
• Online transformation tools and Web services (ICSM Web site)
• Updated transformation software – GDAy
• Surveying equipment firmware to support real-time transformations
• EPSG codes have been registered (GDA2020, MGA2020, Vicgrid2020)
• Adoption of parameters and grid within vendor software (late 2017 onward)
- GIS, Surveying, Engineering, FME
• Open source Python scripts, Excel spreadsheets, NaturalGIS (QGIS) plug-in,
PROJ.4/GDAL/OGR libraries, examples & user guides
• AUSPOS position summary report (GDA94 + GDA2020 + ITRF2014)
• GDA2020 Technical Manual (http://icsm.gov.au/gda/tech.html)
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AHD and AUSGeoid 2020
AHD remains unchanged
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
Open source application
• To convert GNSS heights to AHD
heightsAUSGeoid2020 will be released for use with GDA2020
AUSGeoid09 will still need to be used with GDA94
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Transitioning to GDA2020 The new Geocentric Datum of Australia
Roger Fraser
Office of Surveyor-General Victoria
2017 Vicmap Information Sessions