An evaluation of candidate geomagnetic field models for DGRF 1990 and IGRF 1995

A global evaluation is made of the candidate geomagnetic field models for the DGRF 1990 (main field) and IGRF 1995 (main field and secular variation). An evaluation of these models is also made with respect to the previous (6th generation) IGRF. The models are compared with each other and, where possible, with recent data from observatories, magnetic surveys including repeat stations, Project MAGNET and marine surveys. It is concluded that, although there are some large differences between the candidate models, there is not enough evidence to recommend one model in favour of another. The 6th generation IGRF, however, fits the Project MAGNET data better than any of the candidate models. It is suggested that each model be given equal weight in the production of DGRF 1990 and IGRF 1995 main-field models.