View
1
Download
0
Category
Preview:
Citation preview
Alena Moison, Department of Environment, Land, Water and Planning
05/08/2016
GDA2020 – a modern datum for
Australia
Recent news
2
ABC News Online, Thursday 28th July 2016
GDA2020 specifications
3
• 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
4
Importance of datum
Enables integration of different datasets – measure once, use multiple times
5
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
6
Crustal dynamics
7
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
8
+ AuScope GNSS Stations + AuScope + States StationsBefore AuScope
Infrastructure development
Automated datum maintenance
10
GNSS technology
11
• 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
13
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
14
1.60m
1.49m
Two stage implementation
15
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
16
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.
17
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
18
Transformation grid file
19
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
20
AUSGeoid 2020
21
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
22
Next steps
• Data Audit
• Systems audit
• Educate stakeholders and suppliers
23
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
24
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
25
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
26
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
Recommended