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Enhanced Magnetic Model (EMM2015)

Difference in declination between the EMM and WMM. Declination Comparison of WMM and EMM (larger image)

The Earth's internal magnetic field is a superposition of the field generated by the geodynamo in the liquid outer core (main field) and the field of magnetized rocks in the crust and upper mantle. The main field dominates the long wavelengths, whereas the crustal field dominates at wavelengths smaller than 2500 km.

Geomagnetic field models are conveniently represented as spherical harmonic expansions of a scalar magnetic potential. Such a model can then be evaluated at any desired location to provide the magnetic field vector, its direction, and strength. The standard World Magnetic Model uses a spherical harmonic representation to degree and order 12, resolving the magnetic field at 3000 km wavelength. In contrast, the Enhanced Magnetic Model (EMM) extends to degree and order 720, resolving magnetic anomalies down to 56 km wavelength (see comparison in the figure). The higher resolution of the EMM results in significantly improved pointing accuracy.

The EMM model was compiled from satellite, marine, aeromagnetic and ground magnetic surveys. The EMM 2015 includes data from The European Space Angency's Swarm satellite mission. This constellation of satellites currently represents the best source of data about the evolution of the Earth's main magnetic field.

Why is this important?

Many different applications utilize Earth's magnetic field, whether for navigation, resource evaluation, or research. The magnetic field experienced at or near the Earth's surface is a combination of the main magnetic field, the relatively static crustal magnetic field, and the rapidly time-varying external magnetic field. The better we are able to define these fields, the more accurate the results.


Changes to the code

EMM - Coefficients and Grids


~ Size

Release Date


EMM 2015


May 15, 2015

Enhanced Magnetic Model (EMM2015) and software using the spherical harmonic approach for Windows, Mac, and Linux environments. High CPU requirements (use the faster Mesh software for large number of points), very low RAM requirement (7.5 MB). For use with years 2000 to 2020.

EMM2015 Mesh

4.1 GB

Jan 29, 2016

Enhanced Magnetic Model (EMM2015) software for rapid field calculation using 3D mesh interpolation for Windows and Linux environments. Useful for large grid or profile calculations. Low CPU requirements, high (6 GB) RAM requirement. We recommend a 64 bit computer with a minimum of 16GB RAM for running the software. If you are compiling the software yourself, make sure to use a 64 bit compiler. Only works for years 2015-2020, for 2000-2015 please download the spherical harmonic version above.


The NGDC-720 research model preceded the Enhanced Magnetic Model. The NGDC-720 will not be updated. The archived model and coefficients are provided for software evaluation and testing purposes.