Commission 2: Gravity Field

IAG Commission 2: Gravity Field (2011-2015)

President: Urs Marti (Switzerland)
Vice President: Srinivas Bettadpur (USA)

Terms of Reference and Objectives

Terms of Reference

The accurate determination of the gravity field and its temporal variations is one of the Three Fundamental Pillars of modern geodesy (besides of Geometry and Earth rotation). This is essential for applications in positioning and navigation, metrology, geophysics, geodynamics, oceanography, hydrology, cryospheric sciences and other disciplines related to the Earth’s climate and environment. IAG Commission 2 was established at the IUGG in Sapporo in summer 2003 for promoting, supporting, and stimulating the advancement of knowledge, technology, and international cooperation in the geodetic domain associated with Earth’s gravity field. In the last two periods from 2003 until 2011, Commission 2 has achieved its primary goals and is ready for the next 4-year period. Since most of the scientific themes are of long-term interest, the structure of Commission 2 essentially continues on the same basis as the last period.

Commission 2, at the start of the new period, consists of six sub-commissions (SCs), one project (P) plus several study groups (SGs) and working groups (WGs), all of them jointly with another Commission or a service (JP, JSG, JWG). The sub-commissions cover the following scientific topics:

  • terrestrial, airborne, ship borne gravimetry and relative/absolute gravity networks;
  • spatial and temporal gravity field and geoid modeling;
  • dedicated satellite gravity missions;
  • regional geoid determination;
  • satellite altimetry (established in 2007)
  • gravity and mass displacements (established in 2011)

The former Commission 2 projects for the continental geoid determination (CP2.1 to CP2.6) have been transferred into new regional Sub-Commissions (in analogy to Commission 1) in order to give them a more permanent status inside the IAG. Their principal goal is to improve the collaboration and the data exchange (gravity, GPS/leveling, digital terrain data) inside a certain region and to aim to a geoid model with a higher resolution than satellite only models.

Commission 2 has strong links to other commissions, GGOS, IGFS, ICCT and other components of IAG. Connections to these components are created through joint working groups (JWGs) and joint study groups (JSGs) that provide a cross-disciplinary stimulus for work in several topics of interest to the commission.

The main tasks of Commission 2 in the next four years are among others:

  • Analysis of GOCE data and the release of improved global Gravity field models (satellite only models and in combination with terrestrial data and altimetry)
  • Promoting GRACE follow-on missions for assuring the continued monitoring of global gravity and mass flux changes
  • Defining and Realizing a new Gravimetric Reference System (IGRS) to replace the outdated IGSN71 and assuring the future of the comparison campaigns of absolute gravimeters
  • Establishing of a service for easy accessing Satellite Altimetry data (IAS)
  • Transferring the former 'Global Geodynamics Project' (GGP) into a service 'Global Geodynamics) inside the IGFS.
  • Assisting the IGFS and its components in improving their visibility and their services
  • Assisting GGOS in the realization of a World Height System (WHS)
  • Improve the knowledge of the interaction between gravity change and mass transport (Gravity and Mass Displacement)
  • Assisting the regional sub-commissions in establishing contacts and in acquiring data.

The necessary WGs and SGs can be established at any time and they can be dissolved when they reached their goals or if they are not active.


The main objectives of Commission 2 are as listed in the IAG by-laws:

  • Terrestrial, marine and airborne gravimetry
  • Satellite gravity field observations
  • Gravity field modeling
  • Time-variable gravity field
  • Geoid 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, either independently or at major conferences in geodesy. The activities of its sub-entities, as described below, constitute the activities of the Commission, which will be coordinated by the Commission and summarized in annual reports to the IAG Bureau.

The principal symposium that will be organized by Commission 2 and the IGFS in the next period will be held in Venice in October 2012. A second symposium will be organized by the IGFS in 2014. The other two symposia where a Commission 2 meeting will be held are the IAG scientific assembly 2013 in Potsdam and the IUGG General Assembly 2015 in Prague.

Last Change: December 2014 | page maintained by Urs Marti | Contact