Magnetic variation data for accurate compass navigation.

magnetic declination api

earth, the magnet

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 or variation) 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.

correct your compass with the world magnetic model

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.

Our API enables integration of the WMM with any modern software that supports web API calls.

We offer a 14 day free trial with ongoing subscriptions starting from $100 per month and supported by a Service Level Agreement.


We are validating the API calculations against published experimental data and benchmarking against other models.

The following is an animation of the magnetic declination measured by the SWARM-A satellite over the course of a day. A comparison is made with values predicted by the WMM model accessed through Amentum's API.