1. The Next-Generation Australian Geodetic Datum Benefits and Challenges
Richard Stanaway
QUICKCLOSE Pty Ltd & UNSW
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

2. Acknowledgments
Geoscience Australia – Geodesy and Seismic Monitoring Group
(Gary Johnston, John Dawson, Guorong Hu, Minghai Jia, Anna Riddell,
Craig Harrison, Ryan Ruddick, Bob Twilley)
Geodetic Survey – Office of the Surveyor-General Victoria (OSGV) - DTPLI
(Roger Fraser, Alex Woods)
GPSnet VICMAP Position – DEPI
(Hayden Asmussen, Peter Oates)
CRC SI Positioning Program - Next Generation Datum 1.02
(Chris Rizos, Craig Harrison, Joel Haasdyk, Nic Donnelly, Richard Stanaway)
UNSW - Craig Roberts LINZ – Chris Crook
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

3. The motivation for datum modernisation – Drivers for change and benefits
Maintaining alignment of Australia’s geodetic datum with International Reference Frames (e.g. ITRF and WGS84) – intrinsically used by GNSS
Improved precision for a wider spectrum of users who will use GNSS precise positioning and SBAS
Mitigating unmodelled errors arising from deformation events
(e.g. earthquakes, subsidence)
and plate rotation effects
Meckering, WA
1968
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

4. The future of positioning circa 2030
multi-GNSS
+ augmentation (e.g. SBAS)
+ indoor positioning (e.g. Locata)
+ miniature inertial sensors
4D GIS in the cloud
real-time
precise broadcast
orbits
real-time positions mm
accurate
active transformation model
real-time information currency
authoritative
centralised data
+ clone
ubiquitous
5G/6G wireless
and satellite comms.
(e.g. Beidou, Galileo)
mm/cm accurate real-time personal positioning and navigation – everywhere - No need for explicit use of “coordinates”!
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

5. Spatial Data and Positioning in the future
Complex
time dependent
deformation modelling
Software matches epoch of positioning with epoch of data in order to
maintain context
GNSS Positioning
within ITRF / GGRF
Kinematic
Spatial Data
Data “tagged” with datum and epoch metadata
ESRI
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

6. Rotation of Victorian network – Australian Plate rotation
0.0012” per year
= 0.031” or
8 mm rotation of
a 50 km GNSS baseline
in Victoria
at epoch 2020
GNSS baseline vector computation is in ITRF at epoch of measurement NOT GDA94!
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

7. Station velocities (ITRF) – Victorian AuScope – mm/yr
Computed from GA APREF solution (John Dawson and Guorong Hu)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

8. Positioning precision and plate tectonics
GNSS Reference Frames
(e.g. ITRF2008 and WGS84)
Coordinates of ground features move due to rotation of tectonic plate
(approx. 60 mm/yr in Victoria)
14 parameter
transformation
and / or
deformation model
Static Geodetic Datum
(e.g. GDA94 or GDA2020)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

9. How do we position ourselves now?
Real-time
Single Point-positioning
(SPP)
accuracy
2-10 metres
GNSS reference frame intrinsically ITRF
and transformed to a static frame using 14 parameter model
or Euler Pole
ITRF
NRTK or RTK
Auspos
(using CORS)
accuracy
5-20 mm
ITRF
CORS at
Bald Rock
AuScope
DGNSS and Wide-area RTK
(e.g. OmniSTAR and StarFire)
10 cm – 1 m depending
on level of service
GDA94
ITRF
Precise
Point-
positioning
(PPP)
accuracy
cm-dm
(using IGS or Commercial Orbits )
GDA94
Passive geodetic control
(e.g. PMs, PSMs)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

10. Current compatibility between GNSS usage and GDA94
 Good
 Very good
 Excellent
GPSnet
SMES
NRTK and RTK
data processed in GDA94
Long baseline
plate rotation effect
1 mm per 10 km baseline length
data processed in ITRF and transformed to GDA94 using 14 parameter model – recommended approach
If used as GNSS reference stn.
Most passive control has PU better than 50 mm, but can be more than 1 m (mostly ROs)
Single Point-positioning – WGS 84
(mass market and handheld)
2-10 m precision, so difference marginally noticeable at present
Partial Compatibility
(ITRF only)
ITRF2008 – requires 14 parameter transformation
otherwise ~ 1.2 m difference
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

11. Hierarchy of Reference Frames in Victoria
International
Terrestrial
Reference
Frame
(ITRF)
Hierarchy of Reference Frames in Victoria
Asia-Pacific Reference Frame (APREF)
VICMAP Position - GPSnet
Australian Regional GNSS Network (ARGN) & AuScope
Passive geodetic marks – accessed by SMES
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

12. Current accuracy of GDA94 in Victoria
6 mm
AuScope
GPSnet
Geodetic BMs
HSMs
VICSZ stations
20-50 mm
most PMs
PSMs
e.g. radio masts, towers etc.
Roger Fraser, Manager Geodetic Survey, OSGV - DTPLI
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

13. Stability of Victorian AuScope network mm/yr
Computed from GA APREF solution (John Dawson and Guorong Hu) and ITRF2008 Plate Model (Altamimi et al.)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

14. Localised instability (mining subsidence, clay soil etc.)
From DEPI report -Trial of satellite radar interferometry (InSAR) to monitor subsidence along the Gippsland Coast–
prepared by Linlin Ge and Xiaojing Li, University of New South Wales
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

15. Current roadmap for datum modernisation (ICSM PCG)
1st January 2017
Launch of GDA2020 which is currently proposed to be realised as ITRF2014 propagated to epoch 2020
(1st January 2020).
GDA2020 will supersede GDA94 –
1.5 to 1.6 m difference in coordinates in Victoria
1st January 2020
Launch of kinematic Australian Terrestrial Reference Frame (ATRF) (proposed name). Fully kinematic and continuously aligned with ITRF
Ellipsoid Height changes of ~ 80 mm in Victoria
(will require new Ausgeoid2020 geoid model)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

16. Modernisation of GDA94 not supported by PCG
PCG Option
(from Haasdyk
et al. 2014)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

17. Practical steps to GDA2020 – Surveyors
Managing GPSnet, AllDayRTK, SmartNET, Trimble VRS Now, transition from GDA94 to GDA2020 coordinate delivery – date of changeover – Delivery of coordinates – Use of Ausgeoid2020 (Cannot use Ausgeoid09 with GDA2020).
Implications for ~1.6 m coordinate change for existing users (e.g. Precision Ag.) on projects – require change of project datum and model if currently GDA94? Re-calibrate site calibrations/transformations if currently defined in GDA94.
AusPOS will provide ITRF2014, GDA2020. GDA94 - maybe??
SMES – GDA2020 coordinates and GDA94 - maybe??
GDA2020 Grid Coordinates will be MGA2020
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

18. Practical steps to GDA2020 – GIS Users
Requires direct implementation of direct GDA94 to GDA2020 transformation parameters and distortion grid (not such a problem in Victoria – as GDA94 distortions mostly removed in current state adjustment)
Caution with using WGS84 has hub frame for datum transformations. Caution regarding rotation convention
(e.g. Position Vector (PV) and Coordinate Frame(CF) have opposite signs)
Migration of Vicmap data from GDA94 to GDA2020
Migration of other important GIS datasets (e.g. G-Naf, Vicmap, DCDB, Local Authority, Water, NBN, Electricity, Gas, Roads) to GDA2020. Validation of transformation.
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

19. GIS Pitfalls – null transformations between GDA94, GDA2020 and WGS84 using 7 parameter model
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

20. New datum pitfalls for surveyors watch out for
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

21. Pitfalls continued ....
GDA2020 data CANNOT be overlain on GDA94 data at survey accuracy without using the correct transformation –
1.6 metre misalignment.
Always use full geodetic datum and map grid suffixes
e.g. GDA2020 and MGA2020 – not GDA and MGA
- on all coordinate data and plans.
Use the right transformation parameters and tools
Double-check transformations using known test data.
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

22. GDA94 to GDA2020 – coordinate change (m)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

23. Transformation options from GDA94 to GDA2020
7-parameter transformation
Euler pole transformation (3 parameter)
Absolute deformation model (coordinate shift e.g. NTv2)
7-parameter + residual deformation model (NTv2)
Euler pole + residual deformation model (NTv2)
Transformation options from GDA94 to kinematic ATRF
14-parameter transformation (7 parameters + rates + epoch)
Euler pole transformation (3 parameter + epoch)
Absolute deformation model (coord. shift + rate + epoch)
14-parameter + residual deformation model + epoch
Euler pole + residual deformation model + epoch
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

24. GIS requirement - Alignment of Data in a 2D/3D GIS
Different layers in GIS have to be aligned at a common epoch
for meaningful analysis and data context
(relative precision of layers wrt. each other and datum)
Geodetic Control layer (Datum e.g. GDA94)
Cadastral Layer (GDA94)
Imagery Layer (GDA94?)
Elevation Layer GDA94 (e.g. LiDar)
Utilities Layers (GDA94)
(e.g. Water, Electricity, Optical Fibre)
Existing GDA94 GIS data can be transformed to 2020 or vv.
using a 7 parameter transformation (not computed yet)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

25. Alignment of Data with arbitrary epochs in a 4D GIS
Future challenges –
Alignment of Data with arbitrary epochs in a 4D GIS
Different layers in GIS still have to be aligned at a common epoch
for meaningful analysis and context.
Potential for metre + errors if epoch metadata is ignored
Geodetic Control layer (Kinematic Datum)
e.g. epoch
Cadastral Layer (e.g. epoch )
Imagery Layer (e.g. epoch )
(Raster layer adopted as common epoch for computational efficiency)
Elevation Layer (e.g. LiDar) (e.g )
Water utility Layer (e.g )
Requires universal acceptance and consistent application of kinematic transformation models in all GIS – requires GIS user skill and care!
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

26. Alignment of Data in a 4D GIS
14-parameter transformation or deformation model used to align different epoch layers and data at a common epoch
Geodetic Control layer (Datum)
– e.g transformed to
Cadastral Layer (e.g transformed to )
Imagery Layer (e.g )
(epoch used as common epoch)
Elevation Layer (e.g. LiDar)
(e.g transformed to )
Water utility Layer
(e.g transformed to )
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

27. Challenges – User perspectives and software
Strewth!
I hope our surveyor
has got good PI insurance!!!
A 1.6 m “mistake” is small for many users but can be significant for others!
Terrestrial surveys (e.g. total station, TLS) data epoch is dependent upon epoch of passive control coordinates (are they updated monthly or not?)
Will surveying and CAD software (e.g. Liscad, 12DModel, Terramodel) be able to manage survey data within a kinematic datum?
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

28. Other options for datum modernisation– (e.g. dual-frame)
Positioning in ITRF but consistently transforming positions to an Australian plate fixed frame so that data can maintain local context
(approach adopted in Europe (EUREF), North and South America)
Geodetic Control layer (Kinematic)
– e.g. epoch
14 parameter or Euler pole transformation
Cadastral Layer (epoch 2020)
Imagery Layer (epoch 2020)
Elevation Layer (e.g. LiDar) (2020)
Water utility Layer (epoch 2020)
Requires consistent application of 14-parameter and deformation models in positioning equipment – and surveyor skill!
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

29. Option for a Reference Frame fixed to the Australian Plate (a GDA94 like reference frame)
Defined by Euler pole of the Australian Plate
(Frame moves with stable portion of the Australian Plate)
Station velocities minimised (typically less than 0.2 mm/yr)
Reference epoch has minimal impact on coordinate changes
Distortion free
Linkable directly to ITRF by 3 parameter transformation
(without loss of precision)
Localised deformation can be better visualised and analysed
Supports stability of GIS data management until 4D GIS is fully developed, tested and implemented
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

30. Correction to GDA94 in Victoria if epoch 1994 is maintained (ITRF2014 @ 1994.0) (mm)
This option (modernised GDA94) is not supported by PCG for final ICSM approval
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

31. Datum Modernisation & epoch change - Conclusions
 Benefits of GDA2020 and ATRF
Maintains alignment with ITRF
Supports native GNSS precise positioning
Mitigates effects of deformation and plate rotation
 Challenges
~1.6 metre change in fundamental coordinate system
Requires robust GIS transformation strategy and metadata
Risks if epoch or datum metadata are not managed or communicated in a robust manner
Two-frame option (ITRF and Australian plate fixed frame)
To maximise benefits of both ITRF and modernised GDA94
(until 4D GIS and transformation tools are developed)
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

32. This is an opportunity for surveyors to reclaim the technological high ground with datums, projections and spatial data
Surveyors are the only “experts” in the application and use of geodetic datums in the real world (applied geodesy).
Surveyors are expected to fully understand differences between datums and explain these to clients and other non-expert users.
Surveyors can show leadership by providing advice and support to GIS professionals, managers of spatial data, engineers and project managers.
2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015