Commission 1 - Reference Frames

Final Structure of Commission 1 for the period 2015-2019: President: Geoffrey Blewitt (USA) Vice President: Johannes Böhm (Austria) Terms of Reference Reference systems and frames are of primary importance for much Earth science based research and applications, satellite navigation as well as for practical applications in geoinformation.

Terms of Reference

Reference systems and frames are of primary importance for much
Earth science based research and applications, satellite navigation as well as for practical applications in geoinformation. A precisely defined reference frame is needed for an improved understanding of the Earth’s rotation and its gravity field, sea level change with time, tectonic plate motion and deformation, glacial isostatic adjustment, geocentre motion, deformation due to Earth- quakes, local subsidence and other crustal displacements. 
Commission 1 activities and objectives deal with the theoretical aspects of how best to define reference systems and how reference 
systems can be used for practical and scientific applications. 
Commission 1 will closely interact with the other IAG Commissions, 
ICCT, Services and GGOS components where reference system aspects are of concern. Commission 1 is identical with Sub- commission B2 of COSPAR.


  • Definition, establishment, maintenance and improvement of the geodetic reference frames;
  • Advanced terrestrial and space observation technique development for the above purposes;
  • International collaboration for the definition and deployment of networks of terrestrially-based space geodetic observatories;
  • Theory and coordination of astrometric observation for reference frame purposes.
  • Collaboration with space geodesy/reference frame related international services, agencies and organizations;
  • Promote the definition and establishment of vertical reference systems at global level, considering the advances in the regional sub-commissions;
  • Work to maintain a reference frame that is valuable for global change studies


SC 1.1: Coordination of Space Techniques
Chair: U. Hugentobler (Germany)
SC 1.2: Global Reference Frames
Chair: Xavier Collilieux (France)
SC 1.3: Regional Reference Frames
Chair: C. Bruyninx (Belgium)
SC 1.4: Interaction of Celestial and Terrestrial Reference Frames
Chair: Z. Malkin (Russia)

Steering Committee

  • President: G. Blewitt (USA)
  • Vice President: J. Böhm (Austria)
  • Chair SC 1.1: U. Hugentobler (Germany)
  • Chair SC 1.2: X. Collilieux (France)
  • Chair SC 1.3: C. Bruyninx (Belgium)
  • Chair SC 1.4: Z. Malkin (Russia)

Representatives of Services:

  • IERS: D. Angermann (Germany)
  • ILRS: V. Luceri (Italy)
  • IVS: W. Guangli (China)

SC 1.1 Coordination of Space Techniques

Chair: Urs Hugentobler (Germany)


  • Coordinate research on co-location using common parameters in space
  • Coordinate research on co-location using common parameters at fundamental geodetic observatories
  • Explore the use of new techniques and technologies
  • Interface with IERS WG on Site Survey and Co-location
  • Interface with GGOS JWG on Performance Simulations and Architectural Trade-Offs (PLATO)
  • Interface with Joint WG on Tropospheric Ties

Working Groups

  • 1.1.x Co-Location in Space (not approved – overlap with PLATO)
  • 1.1.1 Co-Location using Clocks and New Sensors (U. Schreiber, Germany)
  • 1.1.2 Scale of the ITRF (T. Herring, USA)

SC 1.2 Global Reference Frames

Chair: Xavier Collilieux (France)


  • Standardization activities: ISO, United Nations Commitee of experts on Global Geospatial Information Management (UN-GGIM) working group on global geodetic reference frame (GGRF), IERS conventions
  • Definition of the global terrestrial reference frame (origin, scale and orientation, time evolution, standards, conventions, models);
  • Enhanced forward modeling of the Earth’s deformation
  • Modeling of the reference frame in general relativity
  • Linking global height system with the terrestrial reference frame
  • Evaluation of systematic errors by focusing on errors at co-location sites 
  • and offset detection methods
  • Methods to determine local tie vectors
  • Impact of multi-technique satellites (space ties)

Working Groups

  • 1.2.1 Offset Detection in Geodetic Coordinate Time Series (S. Williams, UK)

SC 1.3 Regional Reference Frames

Chair: C. Bruyninx (Belgium)

SC 1.3a Europe
Chair: M. Poutanen (Finland)
SC 1.3b South and Central America
Chair: W. Martinez (Colombia)
SC 1.3c North America
Chairs: M. Craymer (Canada) and D. Roman (USA)
SC 1.3d Africa
Chair: E. Saria (Tanzania)
SC 1.3e Asia-Pacific
Chair: J. Dawson (Australia)
SC 1.3f Antarctica
Chair: M. Horwath (Germany)

WG 1.3.1 Time Dependent Transformations between Reference Frames
Chair: Richard Stanaway, Australia

SC 1.4 Interaction of Celestial and Terrestrial Reference Frames

Chair: Zinovy Malkin (Russia)


There are several issues currently preventing the realization of the terrestrial and celestial reference systems (TRF and CRF, respectively) at the mm/µas level of accuracy:

  • Insufficient number and non-optimal distribution of active and stable (systematically and physically) stations (VLBI and SLR in the first place) and radio sources.
  • Technological (precision) limitations of existing techniques.
  • Incompleteness of the theory and models.
  • Not fully understood and agreed-upon details of the processing strategy.

These issues are the subject of research of the IAG Sub-Commission 1.4. 

The SC 1.4 is organized in three Working Groups in close cooperation.

Working Groups

1.4.1 Consistent Realization of ITRF, ICRF, and EOP (M. Seitz, Germany)
1l4.2 Impact of Geophysical and Astronomical Modelling on Reference 
Frames and their Consistency (D. MacMillan, USA)
1.4.3 Improving VLBI-Based CRF for Geodesy (F. Mignard)
Joint Working Groups (2)

Joint Working Groups

JWG 1.1: Site Survey and Co-location (joint with the IERS) Chair: S. Bergstrand (Sweden)
JWG 1.2: Modelling Environmental Loading Effects for Reference Frame Realizations (joint with the IERS) Chair: T. van Dam (Luxembourg) 
JWG 1.3: Definition of Next Generation Terrestrial Reference Frames (joint with ICCT) Chair: C. Kotsakis (Greece)
JWG 1.4: Performance Simulations and Architectural Trade-Offs (PLATO) (joint with GGOS) Chair: D. Thaller (Germany)
JWG 1.5: Strategy for the Realization of the International Height Reference System (IHRS) (joint with GGOS, Commission 2 and IGFS) Chair: L. Sanchez (Germany)
JWG 1.6: Troposphere Ties (joint with Commission 2) Chair: R. Heinkelmann (Germany) 
JWG 2.3: Relativistic Geodesy: First Steps Towards a New Geodetic Technique (joint with Commission 2, ICCT) Chair: J. Flury (Germany)

The ToR can be downloaded using the following link.

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