Resolution No.13 (1981): DGRF1965-75, PGRF1975, and IGRF1980

IAGA, recognising the continuing need for an International Geomagnetic Reference Field, recommends that:

  1. IGRF 1980 be used for the interval 1980 to 1985
  2. DGRF 1965, DGRF 1970, and DGRF 1975 be used, with linear interpolation, for applications requiring definitive values for the interval 1965 to 1975
  3. PGRF 1975 (i.e. DGRF 1975 and IGRF 1980 interpolated linearly) be used for the interval 1975 to 1980 until DGRF 1980 is produced.
  4. This pattern be maintained in future updates.

(In the above text, DGRF denotes a Definitive International Geomagnetic Reference Field, and PGRF a Provisional International Geomagnetic Reference Field. The values of spherical harmonic coefficients for DGRF 1965, DGRF 1970, DGRF 1975, and IGRF 1980 with secular variation terms for 1980-1985 are shown in this publication on page 101.)

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