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Chair: Zuheir Altamimi Head of the IERS ITRF Product Center

UN-GGIM- 2 nd HLF Session 3 Developing an Effective Global Geodetic Reference Framework and Supporting Location-Based Services. Chair: Zuheir Altamimi Head of the IERS ITRF Product Center Institut National de l’ Information Géographique et Forestière (IGN), France

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Chair: Zuheir Altamimi Head of the IERS ITRF Product Center

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  1. UN-GGIM- 2nd HLFSession 3Developing an Effective Global Geodetic Reference Framework and SupportingLocation-Based Services Chair: ZuheirAltamimi Head of the IERS ITRF Product Center Institut National de l’Information Géographique et Forestière (IGN), France E-mail: zuheir.altamimi@ign.fr

  2. Session 3 Presentations • Keynote: Mr. HansjorgKutterer, President, Federal Agency for Cartography and Geodesy, Germany • Panel Discussion: • Mr. UzochukwuOkafor, Surveyor General, Namibia • Mr. John Dawson, Geospatial Reference Systems, Geoscience Australia, Australia • Mr. Alvaro Monett, Executive Secretary, SNIT, Chile • Mr. Nasr Al-Sahhaf, Director, Saudi Space Geodesy Center, Saudi Arabia • Mr. Stefano Ghielmetti, Director, Institutional Business Development, Trimble Navigation • John Dawson: Summary of responses of the geodetic questionnaire • Interventions from the floor

  3. UN-GGIM Objectives • The promotion of global geospatial information to address key global challenges & to support improved decision-making; • At the 2nd Session of the Committee of Experts held in New York in August 2012 nine critical issues were identified, including: • future trends for geospatial information • development of a knowledge base • a global geodetic reference system • a global map for sustainable development

  4. Background: need for a global terrestrial reference system (1/2) • Positioning (determination of point positions or coordinates) is fundamental for • Earth science & Earth observation applications • Geospatial activities, navigation, civil engineering, agriculture, … • Disaster management & reconstruction (Earthquake, Tsunami…) • Coordinates are time dependent • Plate motion --> up to 10 cm/yr • Earthquake dislocation --> up to several meters • To be truly useful, coordinates are (should be) expressed in a terrestrial reference system

  5. Background: need for a global terrestrial reference system (2/2) • Need for a global & unique/standard reference frame --> ensureinter-operability • GNSS is today’s best tool for positioning : • To support science and societal applications • Low-cost, easy to use, with up to few mm precision • Need for Continuously Operating GNSS Core Stations, necessary for: • Access to the global reference frame • Variety of other geodetic & geospatial applications

  6. IAG Structure since 2003 IUGG International Union of Geodesy and Geophysics (IUGG) 65 Member Countries (Adhering Bodies), 8 Associations International Association of Geodesy (IAG) http://www.iag-aig.org Council Executive Committee Bureau Office COB Commission 1 Reference Frames Commission 2 Gravity Field Commission 3 Earth Rotation and Geodynamics Commission 4 Positioning and Applications Inter-Commission Committee on Theory (ICCT) Services: IERS IGS IGFS BGI ICET BIPM IAS ILRS IVS IDS ICGEM IGeS IDEMS PSMSL IBS Global Geodetic Observing System (GGOS)

  7. The International Terrestrial Reference Frame (ITRF) • Established and maintained by the International Earth Rotation and Reference Systems Service (IERS) • Adopted by IAG & IUGG in 1991 & 2007 and by CGPM in 2011 for Earth science & timing applications • Updated every 3-5 years: ITRF88,…,2000,2005 • Current Version: ITRF2008

  8. Key Points • GNSS provides high accuracy for positioning applications • IAG provides the International Terrestrial Reference System (ITRS) on which all GNSS positioning services are based • Implementation of Regional & National geodetic systems depend & rely on the availability of the ITRF • Note the progress of the ITRS implementations at the national level that should continue • Need for UN mandate for the ITRF and its infrastructure ?

  9. backups

  10. What is a Reference Frame in practice? • Earth fixed/centred RF: allows determination of station location/position as a function of time • It seems simple, but … we have to deal with: • Relativity theory • Forces acting on the satellite • The atmosphere • Earth rotation • Solid Earth and ocean tides • Tectonic motion • … Origin, Scale& Orientation • Station positions and velocities are now determined with mm and mm/yr precision

  11. ITRF2008 Network 580 sites (920 stations) 492 IGS/GNSS sites 461 Sites North 118 Sites South

  12. ITRF2008 Site Velocities:time-span > 3 yrs, (σ ~ 0.1 – 1 mm/yr) 509 sites

  13. Access to the ITRF and the IGS role • Any GNSS network can easily be expressed in the ITRF using IGS products (orbit, clocks, ERP: all expressed in the ITRF) • IGS/GNSS observations (RINEX files) & Products are publicly available • IGS products (Orbits, Clocks and Earth Rotation Prameters) to be fixed in regional processing • Geodetic/mathematical procedure to express a GNSS network in the ITRF is also available • NMAs have access to scientific software packages

  14. Processed IGS/GNSS sites, since 1994 652 sites Time series: Red < 5yrs (118), Blue 5-10yrs (138), Green 10-18yrs (396)

  15. Regional & National Reference Systems/Frames • IAG Commission 1 (Reference Frames) ==> Sub-Commission 1.3 (Regional Reference Frames): • EUREF/Europe: ETRS89 • NAREF/North America: NAD83 • SIRGAS/South America: SIRGAS • AFREF/Africa • APREF/Asia & Pacific • SCAR/Antarctica • Regional Reference Frames: rely on the ITRF • Many countries have redefined their geodetic systems to be compatible with/related to ITRF

  16. EUREF Permanent Network (EPN)

  17. AFREF Network

  18. SIRGAS Network

  19. ITRF densification ITRF2008 GNSS sites Densification sites Courtesy Juliette Legrand

  20. GNSS associated reference systems/frames GNSS Ref. System/Frame • GPS (broadcast orbits) WGS84 • GPS (precise IGS orbits) ITRS/ITRF • GLONASS PZ-90 • GALILEO ITRS/ITRF/GTRF • COMPASS CGCS 2000 • QZSS JGS • All are now aligned to the ITRF2008 • WGS84 ≈ ITRF at the decimeter level • GTRF ≈ ITRF at the mm level • -Position using broadcast ephemerides = 150 cm

  21. Why is a Reference Frame needed? • Precise Orbit Determination for: • GNSS: Global Navigation Satellite Systems • Other satellite missions: Altimetry, Oceanography, Gravity • Earth Sciences Applications • Earth rotation • Tectonic motion and crustal deformation • Glacial Isostatic Adjustment (GIA) (= Post Glacial Rebound) • Mean sea level variations • … • Geo-referencing & Positioning applications • Navigation: Aviation, Terrestrial, Ocean • Surveying • Positioning

  22. Current networks: stations observed in 2011 VLBI SLR GPS/IGS DORIS

  23. VLBI, SLR, DORIS sites & their co-locations with GPS 42 32 52

  24. Space Geodesy Techniques Contributing to the ITRF • Very Long Baseline Interferometry (VLBI) • Satellite Laser Ranging (SLR) • DORIS • GNSS:GPS, GLONASS, (Future: GALILEO, COMPASS, QZSS) • ITRF DefiningParameters: • Origin: CoM of the Earth System: defined by SLR • Scale : Consistent with TCG: defined by VLBI & SLR • Orientation: Equatorial: Same for all ITRF versions: Currentlyensured by mainly GNSS/IGS network • ITRF Origin & Scaleare verycritical for science applications, e.g. monitoring of sealevel variation • Science Requirement: ITRF to be stable at 0.1mm/yrlevel

  25. Co-location site • Site where two or more instruments are operating • Surveyed in three dimensions, using classical or GPS geodesy DX(GPS,VLBI) = XVLBI - XGPS SLR/LLR VLBI DORIS GNSS

  26. ITRF Construction IAG Services: IDS IGS ILRS IVS Long-term Solutions DORIS DORIS GPS GPS SLR SLR VLBI VLBI X V Time series stacking Local ties Combination Velocity equality At co-location sites ITRF Solution Station pos & vel & EOPs

  27. ITRF2008 Plate Motion Model Available for 14 platesPlate boundaries: Bird (2003) & MORVEL, DeMets et al. (2010) Eurasia N. America Amur Arabia CARB India Nubia Pacific Sunda Somalia Nazca S. America Australia Antarctica Altamimi et al., JGR, 2012

  28. ITRF Website (itrf.ign.fr)

  29. WGS84 - NGA Stations in ITRF2008 NGA: National Geospatial-Intelligence Agency

  30. ITRF precision (formal errors) Positions Velocities ITRF Accuracy in Origin and Scale ~1 cm (ITRF2008) over its time-span

  31. Access to the ITRF and the IGS role (1/2) • How to express a GNSS network in the ITRF using IGS products (orbit, clocks, ERP: all expressed in the ITRF) ? • Select a reference set of ITRF/IGS stations and collect RINEX data from IGS data centers; • Process your stations together with ITRF/IGS ones: • Fix IGS orbits, clocks and ERPs • Eventually, add minimum constraints conditions in the processing:  = 0 ITRF Your Solution

  32. Access to the ITRF and the IGS role (2/2) ==> Your solution will be expressed in the ITRFyy consistent with IGS orbits • Propagate official ITRF station positions at the central epoch (tc) of the observations: • Compare your estimated ITRF station positions to official ITRF values and check for consistency: • Transformation parameters should be zeros • No outliers: residuals smaller than a certain threshold.

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