International Association of Geodesy. The International Association of Geodesy (IAG) is a constituent association of the International Union of Geodesy and Geophysics focusing on the science which measures and describes the Earth's shape, its rotation and gravity field.

History 
The precursors to the IAG were arc measurement campaigns. The IAG was founded in 1862 as the Mitteleuropäische Gradmessung (Central European Arc Measurement), later became the Europäische Gradmessung (European Arc Measurement) in 1867, the Internationale Erdmessung (Association Geodésique Internationale in French and "International Geodetic Association" in English) in 1886, and took its present name in 1946.

Overview 
At present there are 4 commissions and one inter-commission committee:
 Reference Frames
 Gravity Field
 Geodynamics and Earth Rotation
 Positioning & Applications
 Inter-commission Committee on Theory

International Services 
The twelve IAG Services are split into three general topic areas: geodesy (IERS, IDS, IGS, ILRS, and IVS), gravity (IGFS, ICGEM, IDEMS, ISG, IGETS and BGI) and sea level (PSMSL).

 International Gravimetric Bureau (French: Bureau Gravimétrique International) (BGI)
 International Center for Global Earth Models (ICGEM)
 International Digital Elevation Model Service (IDEMS)
 International DORIS Service (IDS)
 International Earth Rotation and Reference Systems Service (IERS)
 International Geodynamics and Earth Tide Service (IGETS)
 International Gravity Field Service (IGFS)
 International GNSS Service (IGS)
 International Laser Ranging Service (ILRS)
 International VLBI Service for Geodesy and Astrometry (IVS)
 International Service for the Geoid (ISG)
 Permanent Service for Mean Sea Level (PSMSL)

The Global Geodetic Observing System (GGOS) is the observing arm of the IAG that focuses on proving the geodetic infrastructure to measure changes in the earth's shape, rotation and mass distribution. 

The International GNSS Service (IGS), part of GGOS, archives and processes GNSS data from around the world. IGS data is used in the 2021 reference frame (G2139) of WGS84.

Journal 
IAG sponsors the Journal of Geodesy, published by Springer.

Awards 
The IAG's awards for outstanding achievement in geodesy include the Guy Bomford Prize (inaugurated in 1975), the Levallois Medal (inaugurated in 1979), and the IAG Young Author's Award (inaugurated in 1993).

See also 
 Carlos Ibáñez e Ibáñez de Ibero – president of the International Geodetic Association and 1st president of the International Committee for Weights and Measures
 Johann Jacob Baeyer – founder of the Mitteleuropaïsche Gradmessung
 History of geodesy
 History of the metre
 International Geodetic Student Organisation
 Seconds pendulum

References

General references
 
 IUGG Report  (2012) pg 47-50
 IAG History: Photos of the Presidents and Secretaries
 Terrestrial Reference Frames - Connecting the World through Geodesy (2023) GGOS short video

International geodesy organizations
International scientific organizations
International organisations based in Germany
Scientific organizations established in 1940
Earth sciences societies
International geographic data and information organizations