International Geomagnetic Reference Field : Older versions
Older versions of the IGRF models may be downloaded from this page. If you are looking for a model of the geomagnetic field since 1900, you should use the latest IGRF-12 model which is updated retrospectively. However, older versions of the IGRF may be required in special cases. For example, if a magnetic survey was conducted in 1983, the appropriate predictive IGRF-3 (available at that time) would have been subtracted to make an anomaly map. If the original data are no longer available to update the MAP, one has to add the IGRF-3 to the anomaly map and then subtract IGRF-12 which includes the required definitive DGRF model for the period 1980-1985.
The IGRF is a series of mathematical models of the Earth's main field and its annual rate of change (secular variation). The 12 th Generation IGRF coefficients were computed from candidate sets of coefficients produced by the participating members of IAGA Working Group V-MOD. Their institutes and the many organisations involved in operating magnetic survey satellites, observatories, magnetic survey programmes and World Data Centers are to be thanked for their continuing support of the IGRF project.