Release of the World Magnetic Model for 2025 to 2030

The updated World Magnetic Model (WMM) 2025 was released in December 2024, alongside a new WMM – High Resolution version for the first time. The WMM is a spherical harmonic model of the internal magnetic field, designed to provide values of the magnetic field for navigation, heading and direction over 5-years as part of the World Geodetic System 1984 standard coordinate reference frame. WMM is produced jointly by the British Geological Survey and US NOAA National Centers for Environmental Information, funded by the Defence Geographic Centre and National Geospatial Intelligence Agency (NGA), respectively. The WMM is managed by NGA, who define a specification for its performance and accuracy. The WMM is adopted by organisations such as the UK Ministry of Defence, US Department of Defense, NATO, and the International Hydrographic Organisation.

The standard WMM describes the magnetic field to spherical harmonic degree and order 12, while the new High Resolution model includes an extended core field to degree and order 15, and crustal magnetic fields to degree and order 133 (roughly 300km at the equator). The High Resolution model is intended to provide a reference model with greater accuracy for specialist users.

The WMM is released every 5 years, providing a snapshot of the internal field and its predicted rate of change (secular variation), and an uncertainty model. The performance of each WMM release is monitored through its life by comparison to contemporary observations and field models. For the 2025 to 2030 period, we anticipate changes in declination due to evolution of the South Atlantic Anomaly, and a deceleration of the north magnetic pole after rapid acceleration observed in recent years.