The EMM was compiled from satellite, marine, aeromagnetic, and ground magnetic surveys. The EMM2017 includes data from the European Space Agency's Swarm satellite mission. This constellation of satellites currently represents the best source of data about the evolution of Earth's main magnetic field.
Access Methods
To access EMM data, complete one of the following surveys on your intended use. Use EMM 2017 for data from 2000–2022, and EMM2017 Mesh for 2017–2022.
Product Details
The EMM2017 has been updated with improved crustal and core field parts based on the latest track line and satellite magnetic data. The crustal field model of EMM2017 was derived from the latest (2017) release of the Earth Magnetic Anomaly Grid at 2-arcminute resolution, version 3 (EMAG2-v3). EMAG2-v3 is of higher spatial resolution (degree and order 790 of the spherical harmonic expansion) than the crustal field model of EMM2015. The largest differences between these two crustal field models are located in oceanic areas and reflect different methodologies for constructing the underlying EMAGs. NCEI updated the core field (degree and order from 1 to 15) part of EMM2017 based on the Swarm satellite magnetic data. EMM2017 is valid from 2000 to 2022.
Coefficients and Grids
| File | Size | Release Date | Description |
|---|---|---|---|
| EMM 2017 | 24.5MB | July 5, 2017 | Enhanced Magnetic Model (EMM2017) 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 2022. |
| EMM2017 Mesh | 14 GB | July 1, 2018 | Only available for linux. Enhanced Magnetic Model (EMM2017) software for rapid field calculation using 3D mesh interpolation for Windows and Linux environments. Useful for large grid or profile calculations. Low CPU requirements. If you are compiling the software yourself, make sure to use a 64 bit compiler. Only works for years 2017-2022. For 2000-2017, please download the spherical harmonic version above. |
| Older Versions | |||
| EMM 2015 | 24.5MB | 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. |
Background
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 2500km.
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 3000km wavelength. In contrast, the EMM extends to degree and order 790, resolving magnetic anomalies down to 51km wavelength. The higher resolution of the EMM results in significantly improved pointing accuracy.
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 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.
Developing a good model of Earth's crustal magnetic field requires significant amounts of surface or near-surface data. The National Centers for Environmental Information could not have developed the EMM without the support and participation of the following: Satellite data provided by the Swarm Satellite operated by the European Space Agency and the Champ satellite operated by the GFZ German Research Centre for Geosciences.
Trackline data provided by:
- Antarctic Digital Magnetic Anomaly Project
- Australian Geological Survey Organization
- Bedford Institute of Oceanography
- BNDO
- BP Shell Todd
- British Antarctic Survey
- British Oceanographic Data Centre
- Bundesamt Seeschiffahrt Hydrographie
- Bundesanstalt für Geowissenschaften und Rohstoffe
- Bureau of Mineral Resources Australia
- Canadian Hydrographic Service
- Chiba University
- CNEXO
- Diamond Shamrock Petroleum
- DTU IceGra
- Far East Scientific Center
- First Institute of Oceanography
- Geological Survey of Canada
- Geological Survey of Ireland
- Geological Survey of Japan
- GEOMAR Germany
- GEOMER Data Bank ORSTOM Noumea
- Geophysics Division DSIR New Zealand
- GNS Science New Zealand
- GuangZhou Marine Geological Survey MGMR
- Hamilton College
- Hydrographic Department MSA
- Hydrographic Department of Japan
- IFREMER
- Institute de Physique du Globe de Paris
- Institute of Marine Geology/Geophysics USSR
- Institute of Oceanographic Sciences UK
- Jet Propulsion Laboratory
- Kobe University
- Lamont-Doherty Geological Observatory
- Land Information New Zealand
- Mobil
- National Institute of Polar Research Japan
- National Research Institute Oceanology South Africa
- National Science Foundation
- Natural Environment Research Council UK
- NIWA New Zealand
- Ocean Drilling Program at Texas A and M
- Oregon State University
- ORSTOM
- Petrocorp
- Project Magnet
- Rice University
- Royal Netherlands Navy Hydrographic Service
- Russian Academy of Science
- Scripps Institution of Oceanography
- SOA
- South African Data Centre for Oceanography
- South African Geological Survey
- Southampton Oceanography Centre
- Stewart Petroleum
- Texas A and M University
- United Kingdom Hydrographic Office
- United States Geologic Survey
- Universite Francaise Pacifique Tahiti
- University of Alabama
- University of California at San Diego
- University of Cape Town
- University of Hawaii
- University of Rhode Island
- University of Texas at Austin
- University of Texas Institute for Geophysics
- University of the Ryukyus
- University of Tokyo
- University of Witwatersrand
- US National Oceanic and Atmospheric Administration
- US Navy Naval Oceanographic Office
- US Navy NORDA
- Woods Hole Oceanographic Institution
Grids provided by Aeromagnetics of Arabia, India, and the Middle East project; Antarctic Digital Magnetic Anomaly project; Canadian International Development Agency; Coordinating Committee for Geoscience Programs in East and Southeast Asia; Getech; Institut de Physique du Globe de Paris; Southern African Development Community; USGS; Juha Korhonen; Mark Pilkington; Mike Purucker; and Rick Saltus.
More Information
- Contact us at geomag.models@noaa.gov to learn more about individual contributors.
- Visit the CIRES Geomagnetism site to learn more about NOAA - CIRES collaborations in geomagnetism
The work on the Enhanced Magnetic Model is supported through the National Geospatial-Intelligence Agency (NGA), sponsors of the World Magnetic Model.
