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Brief description of geomagnetism and observation systems

About WMM

Learn more about model derivation, uncertainties and magnetic poles

Model & Software

Download model coefficients, software and documentation

Online Calculators

Calculate magnetic field values at or near the Earth surface


Browse imagery and contour maps for main field and secular change

Uses of WMM

Common applications of WMM


License and copyright information

Changes made to the WMM Code and known issues

As changes are made to the WMM code, the revised code will be posted. Check this site for change notices.



Short description of known issue

Aug 23, 2016
The MAG_GetTransverseMercator function converts a latitude and longitude location into UTM parameters. Currently the subroutine outputs wrong UTM parameters. The issue does not affect any of the products we distribute using the Geomagnetism Library, and is primarily for developers seeking to use the Geomagnetism Library for UTM calculations in their software. Contact us at geomag.models@noaa.gov for a workaround.



Short description of changes

Dec 15, 2014
Updated the Geomagnetism Library and software to handle new WMM2015 Error Model. Now distributed with the new WMM2015. Several bug fixes and performance improvements.

Dec 15, 2014
Updated for the new WMM2015 error model. Now distributed with the new WMM2015. Includes self-testing option. Several bug fixes and performance improvements.

Dec 2, 2013
Updates to Mesh implementation of EMM:
-Corrected a bug that caused the executable to fail on some windows machines
-No longer distributing .msh files and program no longer attepts to convert them from binary
-No longer distributing "EGM9615.BIN" file instead information is included in .exe files, in line with our other programs

Apr 20, 2012
The EMM has been extended backward to 2000 using the POMME model.

Apr 20, 2012
Major overhaul of the WMM Sublibrary, which is now called the Geomagnetism Library. It has been reorganized into 5 categories:
-User Interface
-Memory and File Processing
-Conversions, Transformations, and other Calculation
-Spherical Harmonics
The documentation has been updated. Two new functions were added: MAG_YearToDate and MAG_SphericalToCartesian. Several minor pointer related bugs were fixed as well.

Dec 20, 2011
Removed upper limit on altitude. The lower limit was left unchaged at -10 km.

Nov 22, 2011
Removed the Geoid file, "EGM9615.BIN", from the package and added the Geoid data as a header file so it is now a part of the executable. Minor bug fixes and stability improvements were also made.

Jun 16, 2011
Changes in WMM. Fixed minor bugs which threw warnings when WMM was compiled. Fixed memory leak related errors.

Sep 24, 2010
Changes in WMM_SubLibrary.c. Fixed two bugs in WMM_readMagneticModel_Large.

Sep 9, 2010
Changes in WMM_SubLibrary.c 1) Fixed problems due to unclosed files pointers 2) Fixed problems while using "print to file" option in grid programs. Updated WMM header files.

Feb 22, 2010
Users can now enter the height as above MSL or WGS84 Ellipsoid

Feb 4, 2010
GUI now uses the new WMM subroutines. More information on the updates is available in the software package.

Dec 15, 2009
GUI updated with the new WMM2010 coefficients.

July 27, 2007
WMM GUI is released

Feb 4, 2010
Version 1.0 is released. Extensive revision of the sublibrary, point, grid and file processing programs. More information on the updates is available in the software package.

Dec 15, 2009
Version 0.3 is released. Software is updated with WMM2010 coefficients.

Nov 17, 2009
Beta version is released.

Feb 4, 2010
Version 3 is released. This is the last update for this software. Floating point precision changed from single to double. More information on the updates is available in the software package.

Nov 5, 2005
Version 2 is released. Changes include: Spelling corrections in help text and input prompts, Warnings added for undefined declination at / near magnetic poles, Resolution of results consistent across all programs and Corrected elevation bug in the Fortran grid program

Apr 5, 2005
C Software bug fixes: 1) Fixed inclination reporting (erroniously reported as positive upwards) 2) Fixed problem reading input which led to a memory leak and program fail when compiled with gnu compilers

Dec 15, 2004
Changes: As of 2000, the model produced and distributed from the Web has been named "wmm.cof", with the model epoch contained in the header of the model. The current model has an additional change to be compliant with Y2K. The publication date of the model, as shown in the first line (header) of the model is now a four-digit year. There are no changes in the format of the coefficients.

Last Modified on: Wednesday, 25-Jan-2017 22:24:55 UTC
NOAA > NESDIS > NCEI (formerly NGDC)
Maintained by: geomag.models@noaa.gov