In September 2014 BGS contributed MF and SV models for the 12th generation of the International Geomagnetic Reference Field (IGRF). The IGRF is a collaborative model produced by geomagnetists from around the world and endorsed by the International Association of Geomagnetism and Aeronomy (IAGA). The IGRF is a common tool of survey geophysicists and space scientists as a good quality reference model. The IGRF dates back to around 1970 and grew out of discussions that took place within IAGA in the 1960s following the World Magnetic Survey and International Geophysical Year of 1957-1958.
The BGS IGRF candidate models were evaluated alongside those from the other contributing institutes (Denmark, France, Germany, Russia, Switzerland, US). In December 2014, the BGS models for the 2010 MF, 2015 MF and 2015-2020 SV models were accepted and incorporated into IGRF-12.
Currently the IGRF is a spherical harmonic degree 13 model, with maximum harmonic degree 8 for the SV component. Prior to 1995 the IGRF only extends to harmonic degree 10, because of the less dense data distribution that was typical of the pre-Ørsted and pre-Champ satellite eras. The models up to and including 2010 are now designated as ‘definitive’ models (i.e. known as DGRFs), in that the potential for further improving these is regarded by IAGA as slight.