The Earth's magnetic field is generated by electric currents in the molten outer core, and affected by local variations in the mantle and crust. Above the surface, fluctuations of magnetospheric and ionospheric origin are increasingly significant and are impacted by the solar wind. The magnetic field protects us from cosmic radiation and the atmosphere from erosion by the solar wind.
Understanding geomagnetic fields is critical to compass navigation. The direction of magnetic north does not correspond to the geographic north, and a correction (magnetic declination) is required to convert from one to the other.
The direction of the magnetic field vector varies with position and time (the Earth's magnetic poles shift over time). Scientists around the world are studying this variation to improve our understanding of it, and ability to predict changes.
The World Magnetic Model (WMM) is scientific software that calculates magnetic declination, inclination, and intensity at a particular time and position. It is based on data measured by dedicated satellites as part of the SWARM mission and by the ground based observatories of the INTERMAGNET network. It is relied upon throughout the world for navigation, mineral exploration, atmospheric and space science, and is installed on billions of devices in some form. We provide access to WMM2020 via web API.
Read the open API documentation here, and register for access here.