For the second revision of the International Geomagnetic Reference Field (IGRF), the US National Aeronautics and Space Administration (NASA), the UK Institute of Geological Sciences (IGS), and the US Geological Survey (USGS) submitted proposed models of the Earth's main magnetic field at 1965.0, 1970.0, 1975.0, and 1980.0, and its secular variation during 1980-1985. We assessed the proposed models by comparing them with annual mean values from worldwide magnetic observatories data for 1978-1980 from 63 US magnetic repeat stations, and rates-of-change values for worldwide magnetic observatories for 1965-1985 that were derived from straight lines fitted to annual means for 5-yr intervals. We also mutually compared the 1980 models.-from Authors
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Assessment of models proposed for the 1981 revision of the IGRF.