Commission 1 – Reference Frames

President: Urs Hugentobler (Germany)
Vice President: Xavier Collilieux (France)

Terms of Reference

Reference systems and frames are of primary importance as metrological basis for Earth science based research and applications, satellite navigation and orbit determination as well as for practical applications in positioning, mapping and geo-information related fields. A precisely defined and realized reference frame is needed for an improved understanding of the Earth system, including its rotation and gravity field, sea level change with time, tectonic plate motion and deformation, glacial isostatic adjustment, geocenter motion, deformation due to earthquakes, local subsidence, and other crustal displacements. Commission 1 objectives and related activities deal with the theoretical and operational aspects of how best to define and realize reference systems and how those can be used for practical and scientific applications at different spatio-temporal scales on the deformable Earth. Commission 1 will closely interact with the other IAG Commissions and Services, the ICCT, the ICCC, and the GGOS components where reference system aspects are of concern, to address related problems for the realization of celestial and terrestrial reference systems in conformity with present and future accuracy needs. Commission 1 is also linked with the IUGG/COSPAR joint Sub-Commission B2 (International Coordination of Space Techniques for Geodesy) with the aim to develop links and coordinate the work between various groups engaged in the field of space geodesy and geodynamics.

Objectives

The main objectives of Commission 1 are as listed in the IAG by-laws:

• 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.

Program of Activities

Commission 1 fosters and encourages research in the areas of its sub-entities by facilitating the exchange of information and organizing symposia, either independently or at major conferences in geodesy, geophysics and geodynamics. Some events will be focused narrowly on the interests of the sub-commissions and other entities listed below, and others will have a broader commission-wide focus. More specifically, 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;
• Development in the theory 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;
• Interaction with IAG Services IVS, IGS, ILRS, IDS and the IERS, including their Combination Centers and Working Groups as well as with GGOS;
• Encouraging and assisting regional sub-commission countries to re-define and modernize their national geodetic systems so as to become compatible with the ITRF.

The status of Commission 1 with links to the internet sites of its sub-entities and parent and sister organizations and services, will be updated regularly and can be viewed on the web site: https://com1.iag-aig.org/.