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The Next-Generation Australian Geodetic Datum Benefits and Challenges

The Next-Generation Australian Geodetic Datum Benefits and Challenges. Richard Stanaway QUICKCLOSE Pty Ltd & UNSW. 2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18 th April 2015. Acknowledgments. Geoscience Australia – Geodesy and Seismic Monitoring Group

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The Next-Generation Australian Geodetic Datum Benefits and Challenges

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  1. The Next-Generation Australian Geodetic DatumBenefits and Challenges Richard Stanaway QUICKCLOSEPty 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. multi-GNSS + augmentation (e.g. SBAS) + indoor positioning (e.g. Locata) + miniature inertial sensors 4D GIS in the cloud real-time precise broadcast orbits The future of positioningcirca 2030 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. 0.0012” per year = 0.031” 1994-2020 or 8 mm rotation of a 50 km GNSS baseline in Victoria at epoch 2020 Rotation of Victorian network – Australian Plate rotation 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 2014.0 solution (John Dawson and Guorong Hu) 2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

  8. 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) Positioning precision and plate tectonics 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. 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 How do we position ourselves now? 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.  Good  Very good Excellent GPSnet SMES Current compatibility between GNSS usage and GDA94 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. International Terrestrial Reference Frame (ITRF) Asia-Pacific Reference Frame (APREF) Hierarchy of Reference Framesin Victoria 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 2014.0 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. 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 Current roadmap for datum modernisation(ICSM PCG) 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. PCG Option Modernisation of GDA94 not supported by PCG (from Haasdyk et al. 2014) 2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

  17. 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 Practical steps to GDA2020 – Surveyors 2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

  18. 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. Practical steps to GDA2020 – GIS Users 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. 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. Pitfalls continued .... 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. 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 GDA2020 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. 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 2026.45 Cadastral Layer (e.g. epoch 1994.0) Imagery Layer (e.g. epoch 2010.095) (Raster layer adopted as common epoch for computational efficiency) Elevation Layer (e.g. LiDar) (e.g. 2014.98) Water utility Layer (e.g. 2014.0) 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. 2026.45 transformed to 2010.095 Cadastral Layer (e.g. 1994.0 transformed to 2010.095) Imagery Layer (e.g. 2010.095) (epoch 2010.095 used as common epoch) Elevation Layer (e.g. LiDar) (e.g. 2014.98 transformed to 2010.095) Water utility Layer (e.g. 2014.0 transformed to 2010.095) 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 2026.45 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. 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 Option for a Reference Frame fixed to the Australian Plate (a GDA94 like reference frame) 2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

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

  31. Benefits of GDA2020 and ATRF Maintains alignment with ITRF Supports native GNSS precise positioning Mitigates effects of deformation and plate rotation Datum Modernisation & epoch change - Conclusions  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. 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. This is an opportunity for surveyors to reclaim the technological high ground with datums, projections and spatial data 2015 Institution of Surveyors Victoria – Regional Conference – Wangaratta – 18th April 2015

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