World Magnetic Model

[1] The model consists of a degree and order 12 spherical harmonic expansion of the magnetic scalar potential of the geomagnetic main field generated in the Earth's core.

WMM is the standard geomagnetic model of the United States Department of Defense (DoD), the Ministry of Defence (United Kingdom), the North Atlantic Treaty Organization (NATO), the World Hydrographic Office (WHO) navigation and attitude/heading reference, and the Federal Aviation Administration (FAA).

The WMM is produced by the U.S. National Geophysical Data Center (NGDC) in collaboration with the British Geological Survey (BGS).

The model, associated software, and documentation are distributed by the NGDC on behalf of National Geospatial-Intelligence Agency (NGA).

However, due to extraordinarily large and erratic movements of the north magnetic pole, an out-of-cycle update (WMM2015v2) was released in February 2019[4] (delayed by a few weeks due to the U.S. federal government shutdown)[5] to accurately model the magnetic field above 55° north latitude until the end of 2019.