1. IAG Sub-Commission 1.3c Regional Reference Frames for North America 1 Regional Reference Frames for North America Current Status & Future Plans of Regional Sub-Commission 1.3c Michael Craymer Canadian Geodetic Survey Neil Weston U.S. National Geodetic Survey IAG Commission 1 Symposium 2014 Reference Frames for Applications in Geosciences (REFAG) Luxembourg, October 13-17, 2002

2. IAG Sub-Commission 1.3c Regional Reference Frames for North America Objectives  Provide international focus and cooperation for issues involving the horizontal, vertical and three dimensional geodetic networks of North America, including Greenland, Mexico and the Caribbean  Co-Chairs Mike Craymer, Canada Neil Weston, USA (replaced Jake Griffiths in 2013)  Working Groups SC1.3cWG1 – North American Reference Frame (NAREF) SC1.3cWG2 – New Plate-Fixed North American Reference Frame SC1.3cWG3 – Reference Frame Transformations 2

3. IAG Sub-Commission 1.3c Regional Reference Frames for North America WG1 – NAREF  Objective Densify the ITRF/IGS global reference frame in North America Combine regional networks into a continental one Integrate into ITRF via the IGS global network Include most continuous GPS sites in N.A. (2500+ stations) Follow IGS processing guidelines –IGS orbits and EOPs –Current absolute antenna phase center models  Products Weekly coordinate solutions (combinations of regional solutions) Periodic multi-year cumulative (velocity) solutions Presently on hold pending release of IGS repro2 products 3

4. IAG Sub-Commission 1.3c Regional Reference Frames for North America Regional Solutions ContributorSinceSoftwareRegion (# sta used wk 1631) NGS2000PAGESNorth+Central America (762) MIT/PBO 1 2004GLOBKPlate Boundary Obs (183) SOPAC2000GAMITNorth+Central America (140) CGS-B2000BerneseNorthern N.A. (568) CGS-G 2 2001GIPSYCanada (43) PGC 2 2001BernesePacific Northwest (55) INEGI2010GAMITMexico (44) 1 Combo of GIPSY & GAMIT solutions 2 Not contributing since GPS week 1631 (switch to IGS08 & igs08.atx) 4

5. IAG Sub-Commission 1.3c Regional Reference Frames for North America Last NAREF Solutions  Last weekly combination to GPS Week 1513 Too many stations for combination software (2000+) Began development of new software  Last cumulative solution to GPS Week 1399 Prior to switched to IGS05 and absolute phase centre calibrations Need to reprocess all data with new calibrations Not all contributors reprocessed right away  Problem – uneven overlap & redundancy Few stations in all regional solutions Most stations (72%) in only one solution (NGS CORS) – no checks on these sites Causes uneven weighting of stations in combination 5

6. IAG Sub-Commission 1.3c Regional Reference Frames for North America NAREF Velocity Field (Week 1399) 6 HorizontalVertical

7. IAG Sub-Commission 1.3c Regional Reference Frames for North America In the Meantime…  US NGS multi-year solution Covers continental US, Mexico and Caribbean + global RF sites Based on weekly PAGES solutions up to GPS week 1631 (2011.3) Used repro1 products and igs05.atx antenna calibrations with a posteriori correction to igs08.atx using IGS model  NRCan/CGS multi-year solution Covers northern North America, including Greenland (685 stations) Based on weekly Bernese 5.0 solutions up to GPS week 1631 Also used repro1 products and igs05.atx calibrations with a posteriori correction to igs08.atx Densified sparse continuous GPS sites in Canada with 160 Canadian Base Network (repeated high accuracy campaign surveys) Aligned weekly & campaign solutions to IGS08 using global RF sites 7

8. IAG Sub-Commission 1.3c Regional Reference Frames for North America NRCan Multi-Year Solution 8 Horizontal*Vertical * ITRF2008 plate motion removed

9. IAG Sub-Commission 1.3c Regional Reference Frames for North America NGS Multi-Year Solution 9

10. IAG Sub-Commission 1.3c Regional Reference Frames for North America New SINEX Combination Software  Developed by Remi Ferland  Features Dynamic memory allocation (number stations limited only by RAM) Highly optimized and efficient matrix library (LAPACK) Some limited parallelization (adding more) At least 10 times faster than pervious software  Estimates Coordinates & velocities Seasonal signals (annual & semi-annual) Transformations between SINEX files Optional velocity equivalencing: before/after offsets & btwn stations Variance component estimation Post-seismic modelling to be added later 10

11. IAG Sub-Commission 1.3c Regional Reference Frames for North America Future Plans  Reprocessing of regional solutions with repro2 Most contributors plan to reprocess Will include more overlap among networks NGS may be delayed due to their large network  Restart NAREF combinations in IGS13 Current weekly combinations & submissions to IGS Weekly regional combinations of repro2 regional solutions Cumulative solutions with monthly updates  Need discontinuity detection software Can’t manually inspect thousands of stations Will evaluate various software for automatic detection 11

12. IAG Sub-Commission 1.3c Regional Reference Frames for North America WG2 – Plate-Fixed N.A. Reference Frame  Problems with NAD83 Offset ~2 m from geocentre (ITRF) Defined by transformation from ITRF but biased by 2 mm/y error in NUVEL-1A  Objective Establish a new high-accuracy, geocentric reference frame, including velocity models, procedures and transformations, tied to the stable part of the North American tectonic plate. Replace NAD83 together with US vertical datum by 2022  Reference frame definition – current thinking Use current ITRF in 2022 at some adopted reference epoch Estimate plate motion to keep frame aligned to N.A. plate Need to select a set of frame sites representing stable N.A. 12

13. IAG Sub-Commission 1.3c Regional Reference Frames for North America Future Plans  Begin discussions with public Initial discussions held at the Federal Geospatial Summit in 2010 NGS plans to begin active promotion in near future  US Foundation CORS To provide a more stable network to define the new frame Creating a network of 10-20 highly stable CORS sites Owned and operated by NGS (complete control) Using highly stable monumentation Will try to collocate with other other techniques (GGOS stations) Will contribute stations to the IGS network First site currently being installed in Miami this week 13

14. IAG Sub-Commission 1.3c Regional Reference Frames for North America WG3 – Reference Frame Transformations  Objectives To determine consistent relationships between international, regional and national reference frames/datums in North America Maintain and update these relationships Provide tools for implementing the transformations Primarily involves maintaining the adopted relationship between ITRF and NAD83  NAD83 – ITRF NAD83 is now defined by a transformation from ITRF96 Transformation is incrementally updated to new ITRF’s using adopted IERS transformations between ITRF realizations NNR-NUVEL-1A is used to keep the frame fixed to N.A. (now known to be biased by about 2 mm/yr) Will update transformation for new ITRF2013 14

15. IAG Sub-Commission 1.3c Regional Reference Frames for North America Other N.A. Activities  Commercial RTK networks Commercial RTK networks effectively acting as access points to NAD83 for many users Problem – RTK networks integrated into different realizations of NAD83 Canada is now integrating 6 largest RTK networks in latest realization of NAD83 (600+ stations) Also implementing a validation process based on these results NGS planning to implement a similar RTK validation program 15

16. 16 CACS and Commercial RTK Networks

17. IAG Sub-Commission 1.3c Regional Reference Frames for North America Thank you for your attention 17