The 1995 revision of the International Geomagnetic Reference Field (IGRF) includes a definitive main-field model for 1990.0, a main-field model for 1995.0, and a forecast secular variation model for the interval 1995-2000. The four 1990.0 main-field models and four 1995.0 main-field models that were proposed as candidates have been evaluated by comparing them one with another, and also with magnetic observatory data. The comparisons indicate that the accuracies of the main-field models proposed by IZMIRAN are one and a half times higher than those of the other candidate models. The two secular variation models that were proposed have also been compared; averaging of the two models is appropriate.

The method of natural orthogonal components (NOC) analysis, which separates temporal variations, and spherical harmonic analysis, which models spatial distribution, were combined to model the spatial-temporal variations of the geomagnetic field over the globe. NOC's obtained in this way describe the temporal variations year by year without smoothing. Use of combined observatory and satellite magnetic survey data for developing a spatial-temporal model of equal accuracy on the globe and over the time interval of the data is proposed.

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