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Geomagnetic Calculators, Maps, Models and Software

Online Calculators

NGDC hosts online calculators to compute the geomagnetic field at any location on the Earth. The geomagnetic models behind these calculators are regularly updated to maintain their accuracy. We are currently hosting revised on-line calculators for the IGRF+ (1590-2020), DoD WMM (2015-2020), Declination only (1590-2020), and US Historic Declination (1750-2020).


NGDC hosts a mapviewer for historical declination at NGDC mapping page. The world maps of all the components of the geomagnetic field, calculated from the latest WMM model (WMM2015) are available for at the WMM home page (click the map on the lower left). Use the IAGA Web Image Spreadsheet Tool (Wist) to display and download IGRF magnetic field maps and data from 1900 - 2015. The Wist allows the user to select the number of rows (years) and columns (magnetic elements) to display. Each "cell" of the Wist displays the appropriate map for the selected year and element and links to the PDF for a higher resolution version of the map and to the data used to create the map.

Geomagnetic main-field models

Because the Earth's magnetic field is constantly changing, it is impossible to accurately predict what the field will be at any point in the very distant future. By constantly measuring the magnetic field, we can observe how the field is changing over a period of years. Using this information, it is possible to create a mathematical representation of the Earth's main magnetic field and how it is changing. Since the field changes the way it is changing, new observations must continually be made and models generated to accurately represent the magnetic field as it is. NGDC participates in the development and distribution of two global main-field models, the World Magnetic Model and the International Geomagnetic Reference Field Model. The WMM is the standard navigation model for the U.S. and U.K. Departments of Defense and NATO. The IGRF is the international research reference model. To learn more about these models, visit the home Web sites for the US / UK World Magnetic Model (WMM) 2015 and IAGA IGRF-12. Before using the IGRF please look at the 'Health Warning'.

High Resolution Models

NGDC also provides geomagnetic models with higher spatial resolution than the above models. These models include the magnetic field contributions from the Earth's crust. These models are suitable for applications where higher navigational accuracy is required.

The EMM2015 is an epoch 2015 release of the Enhanced Magnetic Model, intended to calculate the magnetic field for both the Earth's internal magnetic field as well as the crustal field. It extends to degree and order 720, resolving magnetic anomalies down to 56 km wavelength. It is updated along the same schedule as the standard World Magnetic Model.

The HDGM is a product of NGDC which is updated annually. It includes the internally generated Main Field, the secular variation of the field, the crustal field to degree and order 720, and a basic model for the external field. To purchase the model contact us. For more details see our HDGM page!


Stand-alone software, suitable for running on personal computers are provided for the various geomagnetic models distributed by NGDC.

  • Geomag 7.0 C software and model is released! The updated igrf12.cof required by many users is now available along with the new Geomag 7.0 software. (Windows version, Linux tar file).
  • Download IAGA's current International Geomagnetic Reference Field (IGRF)
    • Visit the IAGA Web to learn more about the IGRF.
  • Download the collection of Utility Programs. Source code has been added for a selection of the programs.
    Programs include (partial list):
    GMCORD program which determines the geomagnetic coordinates for any selected global location.
    SQ1MODEL program which produces an estimate of the daily variation of field for any global location
    DSTDEMO program illustrates the change of the DST mid-latitude fields during a storm
    SUNMOON program gives the position of the Sun and Moon for any observer latitude, longitude and selected time

Collaborative research with the University of Colorado

In addition to the standard model products, NGDC, in collaboration with the Cooperative Institute for Research in the Environmental Sciences (CIRES), has several research products available. To learn more about the CIRES/NGDC geomagnetic research efforts, visit the CIRES Geomagnetism Web site.