chair: zuheir altamimi head of the iers itrf product center

UN-GGIM HLF, Session 3, Doha, February, 2013

UN-GGIM- 2nd HLFSession 3

Developing an Effective Global Geodetic Reference Framework and Supporting

Location-Based Services

Chair: Zuheir AltamimiChair: Zuheir Altamimi

Head of the IERS ITRF Product CenterInstitut National de l’Information Géographique et

Forestière (IGN), France

E-mail: [email protected]


• Keynote: Mr. Hansjorg Kutterer, President, Federal Agency for Cartography and Geodesy, Germany

• Panel Discussion:1. Mr. Uzochukwu Okafor, Surveyor General, Namibia

2. Mr. John Dawson, Geospatial Reference Systems, Geoscience Australia, Australia

3. Mr. Alvaro Monett, Executive Secretary, SNIT, Chile

4. Mr. Nasr Al-Sahhaf, Director, Saudi Space Geodesy Center, Saudi Arabia

5. Mr. Stefano Ghielmetti, Director, Institutional Business Development, Trimble Navigation

6. John Dawson: Summary of responses of the geodetic questionnaire

7. Interventions from the floor

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Session 3 Presentations

Exchange Forum, Doha, February, 2013

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

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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

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Background: need for a global terrestrial reference system (2/2)

• Need for a global & unique/standard reference frame --> ensure inter-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

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IAG Structure since 2003

Commission 4Positioning and

Applications

Commission 1

Reference Frames

Commission 2

Gravity Field

Commission 3Earth Rotation and

Geodynamics

International Union of Geodesy and Geophysics (IUGG)65 Member Countries (Adhering Bodies), 8 Associations

International Association of Geodesy (IAG)

Executive Committee OfficeCouncil COB

BIPM

IVS PSMSL

IGS

Global Geodetic Observing System (GGOS)

Services:

IGeS

IAS

IDSILRS IDEMSICGEM IBS

BGIIGFSIERS ICET

Inter-Commission Committee on Theory (ICCT)

Bureau

IUGG

http://www.iag-aig.org


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

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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 ?

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• backups

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UN-GGIM HLF, Session 3, Doha, February, 2013 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


ITRF2008 Network

580 sites (920 stations)

461 Sites North

118 Sites South

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492 IGS/GNSS sites


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

509 sites

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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

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Processed IGS/GNSS sites, since 1994

Time series: Red < 5yrs (118), Blue 5-10yrs (138), Green 10-18yrs (396)

652 sites


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

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EUREF Permanent Network (EPN)

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AFREF Network

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SIRGAS Network

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ITRF densification

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ITRF2008 GNSS sites Densification sites

Courtesy Juliette Legrand


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

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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

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Current networks: stations observed in 2011

VLBI SLR

GPS/IGS DORIS


VLBI, SLR, DORIS sites & their co-locations with GPS

52324223


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 Defining Parameters:– Origin: CoM of the Earth System: defined by SLR

– Scale : Consistent with TCG: defined by VLBI & SLR

– Orientation: Equatorial: Same for all ITRF versions: Currently ensured by mainly GNSS/IGS network

• ITRF Origin & Scale are very critical for science applications, e.g. monitoring of sea level variation

• Science Requirement: ITRF to be stable at 0.1mm/yr level


SLR/LLR

DORIS

VLBI

GNSS

DX(GPS,VLBI) = XVLBI - XGPS

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Co-location site• Site where two or more instruments are operating• Surveyed in three dimensions, using classical or GPS geodesy


ITRF Construction

Time series stacking X V

Velocity equality

Local ties

Combination

ITRF Solution

At co-location sites

DORISGPS

SLRVLBI

DORISGPS

SLRVLBI

Long-term SolutionsIAG Services:IDS IGS ILRS IVS

Station pos & vel& EOPs


Eurasia

N. Ameri

ca

Nubia

Som

alia

S. A

mer

ica

Australia

Pacific

Antarctica

Indi

a

Naz

caArabia

Amur

Sund

aCARB

ITRF2008 Plate Motion Model Available for 14 plates

Plate boundaries: Bird (2003) & MORVEL, DeMets et al. (2010)

Altamimi et al., JGR, 2012


ITRF Website (itrf.ign.fr)

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WGS84 - NGA Stations in ITRF2008

NGA: National Geospatial-Intelligence Agency

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ITRF precision (formal errors)

ITRF Accuracy in Origin and Scale~1 cm (ITRF2008) over its time-span

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Positions Velocities


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

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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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chair: zuheir altamimi head of the iers itrf product center

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