International Geomagnetic Reference Field: 14th Generation IGRF: 14th Generation
Model Background
The International Geomagnetic Reference Field (IGRF) is a model of the Earth's main magnetic field that is updated every 5 years; the first version of the IGRF was created in 1965. The creation and updating of the IGRF is a collaborative project involving many countries, research institutions, and scientific organizations.
The British Geological Survey plays an important role in updating the IGRF and provides an online calculator.
Web Service
The 3D viewer is powered by the open-source Cesium library, under the Apache 2.0 license. This library requires that your device can run WebGL. Performance may suffer on older devices. The 2D map view is powered by Leaflet, which is also open-source.
Swarm satellite positions are made available via the ViRES HAPI interface.
Contour Generation
Maps on in this webservice are produced using the International Geomagnetic Reference Field (IGRF), 14th Generation, as released in Dec 2024. Values are computed at mean sea-level (h=0 km) for every year spanning 1900-2030. Each magnetic field component can be shown.
Note: Declination has a discontinuity at the ±180° boundary - contouring algorithms thus perform poorly at the poles and the contour lines should be viewed with caution.
Pure Python International Geomagnetic Reference Field (PPIGRF) was used to compute field values and GeoJSON files produced using geojsoncontour. The GeoJSON files are available from our API.
Secular Variation
Secular variation (SV) is determined in 5-year periods from the IGRF and describes the rate of change of the geomagnetic field components per year. Gridded values were calculated using a Fortran script written by the BGS geomagnetism team. For those unfamiliar with FORTRAN, this program can be compiled with f2py and called from Python.
This program calculates the secular variation for X, Y, Z and F. Secular variation for H, D and I are then found as following:
Declination (D) SV is not yet provided in this web service but can be computed from the Python or FORTRAN code.