2024-08-05

Commission 2 – Gravity Field

President: Srinivas Bettadpur (USA)
Vice President: Tao Jiang (China)

Terms of Reference

The accurate determination of the gravity field and its temporal variations is one of thethree fundamental pillars of modern geodesy (next to geometry/kinematics and Earthrotation). This is essential for applications in positioning and navigation, civil andaerospace engineering, metrology, geophysics, geodynamics, oceanography, hydrology,cryospheric sciences and other disciplines related to the Earth’s climate and environ-ment. IAG Commission 2 was established at the IUGG in Sapporo in summer 2003for promoting, supporting, and stimulating the advancement of knowledge, technol-ogy, and international cooperation in the geodetic domain associated with the Earth’sgravity field.

Since most of the scientific themes are of long-term interest, large parts of thestructure of Commission 2 are continued on the same basis as in the previous period2020-2023. Main drivers for the activities of the present period 2023-2027 are relatedto the IAG resolution adopted at the XXVIII IUGG General Assembly 2023 in Berlin,concerning the International Terrestrial Gravity Reference System (ITGRS).

Commission 2, at the start of the new period, consists of six sub-commissions (SC),plus Study Groups (SG) Joint Working Groups (JWG) and Joint Study Groups (JSG),all of them jointly with other Commissions and/or services. The sub-commissions coverthe following scientific topics:

  • Terrestrial (land, marine, airborne) gravimetry and relative/absolute gravity net-works;
  • Geoid, Physical Height Systems and Vertical Datum Unification;
  • Satellite gravity missions;
  • Regional geoid determination;
  • Satellite altimetry;
  • Gravity inversion and mass transport in the Earth system.
Commission 2 has strong links to other commissions, GGOS, IGFS, ICCT andother components of IAG. Connections to these components are created through JWG and JSG that provide a cross-disciplinary stimulus for work in several topics of interestto the commission, and the joint organization of meetings.

The main tasks of Commission 2 in the period 2023-2027 are among others:

  • Establishment of a Global Absolute Gravity Reference System (GAGRS) to replacethe International Gravity Standardization Net 1971 (IGSN71), which no longer ful-fills the requirements and accuracy of a modern gravity reference; especially toinclude time-dependent gravity variations;
  • Supporting the realization of an International Height Reference System (IHRS);
  • Supporting the realization of a Global Geodetic Reference System (GGRS);
  • Analysis of current and future satellite data (CHAMP, GRACE, GOCE, GRACE-FO) and the release of improved global gravity field models (satellite-only modelsand in combination with terrestrial data and satellite altimetry);
  • Promoting future gravity mission constellations for assuring the continued monitoring of global gravity and mass transport processes in the Earth system;
  • Assuring the future of the comparison campaigns of absolute gravimeters;
  • Investigating modern relativistic methods and geodetic metrology with special focuson gravity field and height determination;
  • Fostering regional gravity and geoid determination and integration of regionalmodels into a global reference;
  • Understanding of physics and dynamics of the Earth sub-systems and masstransport processes in the Earth system;
  • Providing contributions to operationalization of mass transport modelling andstimulation of new applications;
  • Fostering communication with user communities;
  • Assisting the IGFS and its components in improving their visibility and theirservices;
  • Assisting the regional sub-commissions in establishing contacts and in acquiring data.

Objectives

The main objectives of Commission 2 are as listed in the IAG Bylaws:

  • Terrestrial, marine and airborne gravimetry
  • Satellite gravity field observations
  • Gravity field modeling
  • Time-variable gravity field
  • Geoid and height determination
  • Satellite orbit modeling and determination
  • Satellite altimetry for gravity field modeling

Program of Activities

The Gravity Field Commission fosters and encourages research in the areas of its sub-entities by facilitating the exchange of information and organizing Symposia, eitherindependently or at major conferences in geodesy. The activities of its sub-entities, as described below, constitute the activities of the Commission, which will be coordinatedand summarized in annual reports to the IAG Bureau.

The principal symposia that will be organized jointly by Commission 2 and theIGFS in the next period will be held in September 2024 in Thessaloniki and in 2026(location TBD). The other two symposia where a Commission 2 meeting will be heldare the IAG Scientific Assembly 2025 in Rimini, Italy and the IUGG General Assembly2027 in Incheon, South Korea.

The status of Commission 2, with links to the internet sites of its sub-entities andparent and sister organizations and services, will be updated regularly and can beviewed on the web site: https://com2.iag-aig.org/.

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