[1][2] As early as 1861, Johann Jacob Baeyer sent a memorandum to the King of Prussia recommending international collaboration in Central Europe with the aim of determining the shape and dimensions of the Earth.

This involved determining the geoid by means of gravimetric and leveling measurements, in order to deduce the exact knowledge of the terrestrial spheroid while taking into account local variations.

Baeyer developed a plan to coordinate geodetic surveys in the space between the parallels of Palermo and Freetown Christiana (Denmark) and the meridians of Bonn and Trunz (German name for Milejewo in Poland).

[6][7][8] The International Geodetic Association gained global importance with the accession of Chile, Mexico and Japan in 1888; Argentina and United-States in 1889; and British Empire in 1898.

However, the activities of the International Latitude Service were continued through an Association Géodesique réduite entre États neutres thanks to the efforts of H.G.

[2][1] At present there are 4 commissions and one inter-commission committee: 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).