Users rush to update crucial navigation systems

Hundreds of thousands of users will be rushing to update their navigation systems after the launch of a new model tracking magnetic north, which is crucial to the accuracy of global positioning systems (GPS) that are relied upon across the world.

In partnership with the UK Defence Geographic Centre and the US National Geospatial-Intelligence Agency (NGA), the British Geological Survey (BGS) and the US National Oceanic and Atmospheric Administration (NOAA) have teamed up to update the World Magnetic Model (WMM).

Standard model

The WMM is the standard model used by the United Kingdom and the United States governments, including the U.S. Federal Aviation Administration and the U.S. Department of Defense, as well as organizations with an international remit such as the North Atlantic Treaty Organization (NATO), the International Hydrographic Organization and the UK Hydrographic Office.

The model comprises a series of magnetic field maps that track changes in the magnetic field, such as the spot at which compass needles point in the northern hemisphere. To ensure pinpoint accuracy, it is crucial that the shifts in magnetic north, which are caused by flow of the liquid iron in the outer core of the Earth, are taken into account in the electronic equipment that is trusted to guide global trade and enable the safe transit of travellers across the planet. From GPS-enabled mobile phones to nuclear submarines, this improved resolution update, released last month, will allow navigation with more accuracy than ever before to take place.

“The WMM was officially released in December, ensuring users can have the most up-to-date information so they can continue to navigate accurately for the next five years" said Dr William Brown, global geomagnetic field modeller at BGS.

He continued, "The current behaviour of magnetic north is something that we have never observed before. Magnetic north has been moving slowly around Canada since the 1500s but, in the past 20 years, it accelerated towards Siberia, increasing in speed every year until about five years ago, when it suddenly decelerated from 50 to 35 km per year, which is the biggest deceleration in speed we’ve ever seen.”

Travel impact

While each model predicts how magnetic north will shift over the five-year period to limit any error, the change will have an impact on travellers.

Imagine someone was planning to travel by sleigh from a chimney top in South Africa to a snow covered-roof in the UK, a journey of around 8500 km. Using the previous WMM and setting off just one degree off-course, he would end up approximately 150 km away from where he should [1]. With a margin of error of only a few inches between chimney flues, this could cause significant issues.

Values from the updated model can now be calculated, and the WMMHR2025 and the WMM2025 are available for download.

Two new versions

This year marks the first year that two versions of the model are being released. In addition to WMM2025, the 2025 update features the first-ever WMM High-Resolution 2025, which includes improved spatial resolution of approximately 300 km at the equator compared to the standard spatial resolution of 3300 km at the equator. Higher resolution provides greater directional accuracy through enhanced precision in the data.

Sponsored by NGA and the Defence Geographic Centre, the WMM is produced by BGS and NOAA’s National Centers for Environmental Information. It is the standard model used by the US Department of Defense, the UK Ministry of Defence, NATO and the International Hydrographic Organization for navigation, attitude and heading referencing systems using the geomagnetic field.

It is also used widely in civilian navigation and heading systems. The WMM is updated every five years and its accuracy is validated annually to ensure it falls within the WMM military specification.

[1] It is believed that, while such a traveller may not rely primarily on satellite navigation, no logistical expert delivering hundreds of years of consistent service would not have such technology as a backup in case of emergency.

Source: British Geological Survey