IAG Commission 1: Reference Frames

President: Geoff Blewitt, University of Nevada, Reno, USA

Vice-President: Johannes Böhm, Technische Universität Wien, 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 geo-information. 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 deploy-ment 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 m
  • aintain a reference frame that is valuable for global change studies

Program of Activities

The program of activities for Commission 1 includes:

  • Theoretical and applied research activities related to reference frames;
  • Research and development activities that impact the reference frame determination and its accuracy, as well as, the best and optimal usage of reference frames in Earth Science applications;
  • Interaction with all established IAG Services: IVS, IGS, ILRS, IDS and the IERS, including their Combination Centres and Working Groups;
  • Development in the theory and application of the transformation between Celestial and Terrestrial Reference Systems and application of the theory to improve the consistency between ICRF, ITRF and EOPs, in cooperation with IVS and IERS;
  • Exploration of advanced methodologies for the combination of products and raw observations of space geodetic techniques;
  • Investigation of systematic error sources and factors limiting the precision of space geodetic techniques and their combination;
  • Encouraging and assisting regional sub-commission countries to re-define and modernize their national geodetic systems so that they are compatible with the ITRF;
  • Establishment of a dedicated Web site relating all Commission 1 activities.

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