Dataset Overview | National Centers for Environmental Information (NCEI)

EMAG2v3: Earth Magnetic Anomaly Grid (2-arc-minute resolution)

browse graphicEMAG2v3 showing the west coast of the United States and Canada. The stripes are magnetic lineations due to sea-floor spreading.
EMAG2v3 is a global Earth Magnetic Anomaly Grid compiled from satellite, ship, and airborne magnetic measurements. It is a significant update of the previous release of the Earth Magnetic Anomaly Grid. The resolution remains 2 arc-minutes, and the altitude of 4 km above the geoid is still supported, but an additional product, a grid that is observed at sea-level over oceanic regions, has been produced. New additions grid and track line data have been included, both over land and the oceans. Wherever available, the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids. Interpolation between sparse track lines in the oceans was improved by using a kriging algorithm, which specializes in heterogeneous data distribution gridding, in order to create a compilation as true to the observed data as possible, and avoid using a priori information. The longest wavelengths (>300 km) were replaced with the latests satellite lithosphere magnetic field model, MF7.
  • Cite as: Brian Meyer; Richard Saltus; and Arnaud Chulliat. 2017: EMAG2v3: Earth Magnetic Anomaly Grid (2-arc-minute resolution). Version 3. NOAA National Centers for Environmental Information. https://doi.org/10.7289/V5H70CVX. Accessed [date].
gov.noaa.ngdc.mgg.geophysical_models:EMAG2_V3
Download Data
  • EMAG2v3 ASCII CSV data file (download)
    Zip file containing the comma delimited ASCII grid that contains i and j grid indicies, latitude and longitude cell centered location information, magnetic anomalies at a consistent 4km elevation, sea level over oceanic regions, anomaly source grid code, and an error estimate for each cell.
  • EMAG2v3 Format Description (download)
    ASCII text file that contains format description of the EMAG2v3 CSV data file.
  • EMAG2v3 Full Resolution Map of Upward Continued Anomalies (download)
    PNG of EMAG2v3 as a poster at a consistent 4km altitude.
  • EMAG2v3 Full Resolution Map of Sea Level Anomalies (download)
    PNG of EMAG2v3 as a poster at sea level over oceanic regions.
  • Upward Continued Google Earth Image (download)
    KMZ plugin for Google Earth of EMAG2v3 as a poster at a consistent 4km altitude with data gaps filled with MF7 values. Requires installation of Google Earth.
  • Upward Continued GIS TIFF (download)
    A georeferenced TIFF (GeoTIFF) for EMAG2v3, where the altitude is at a consistent 4km altitude, with a resolution of 2 arc-minutes, which can be opened by ESRI ArcGIS or any other GIS application. The values (nT) are stored as 32-bit floating point.
  • Sea Level GIS TIFF (download)
    A georeferenced TIFF (GeoTIFF) for EMAG2v3, where the altitude is at sea level over oceanic regions, with a resolution of 2 arc-minutes, which can be opened by ESRI ArcGIS or any other GIS application. The values (nT) are stored as 32-bit floating point.
  • Map of Source Grid Codes (download)
    PNG of EMAG2v3 codes to designate which grid is primarily responsible for the anomaly value for each cell.
  • Map of Estimated Error Values (download)
    PNG of EMAG2v3 estimates of the error in nanoTesla for each cell.
Distribution Formats
  • XYZ/Zip (Version: Version 3)
    • File Specification: Comma delimited ASCII grid that contains i and j grid indicies, latitude and longitude cell centered location information, magnetic anomalies at a consistent 4km elevation, magnetic anomalies at sea level over oceanic regions, anomaly source grid code, and an error estimate for each cell.
  • ASCII TXT (Version: Version 3)
    • File Specification: An ASCII text file which describes the format of the CSV data grid.
  • PNG (Version: Version 3)
    • File Specification: Full Resolution Map of EMAG2v3 as a poster at a consistent 4km altitude
  • PNG (Version: Version 3)
    • File Specification: Full Resolution Map of EMAG2v3 as a poster at sea level over oceanic regions
  • KMZ (Version: Version 3)
    • File Specification: Plugin for Google Earth of EMAG2v3 as a poster at a consistent 4km altitude with data gaps filled with MF7. Requires installation of Google Earth.
  • GIS TIFF (Version: Version 3)
    • File Specification: A georeferenced TIFF (GeoTIFF) for EMAG2v3, where the altitude is 4km altitude above continental regions and sea level over oceanic regions, with a resolution of 2 arc-minutes, which can be opened by ESRI ArcGIS or any other GIS application. The values (nT) are stored as 32-bit floating point.
  • PNG (Version: Version 3)
    • File Specification: Full Resolution Map of EMAG2v3 codes to designate which grid is primarily responsible for the anomaly value for each cell
  • PNG (Version: Version 3)
    • File Specification: Full Resolution Map of EMAG2v3 estimates of the error in nanoTesla for each cell
Ordering Instructions Contact NCEI for other distribution options and instructions.
Distributor NOAA National Centers for Environmental Information
ncei.info@noaa.gov
Dataset Point of Contact NOAA National Centers for Environmental Information
ncei.info@noaa.gov
Dataset Point of Contact NCEI Geomagnetic Modeling Team
NOAA National Centers for Environmental Information
geomag.models@noaa.gov
Time Period 1946-01-01 to 2014-02-20
Spatial Reference System urn:ogc:def:crs:EPSG::4326
Spatial Bounding Box Coordinates
N: 90
S: -90
E: 360
W: 0
Spatial Coverage Map
General Documentation
Associated Resources
Publication Dates
  • publication: 2017-05-30
Edition Version 3
Data Presentation Form mapDigital
Dataset Progress Status Complete - production of the data has been completed
Historical archive - data has been stored in an offline storage facility
Data Update Frequency As needed
Purpose Magnetic anomaly maps provide insight into the subsurface structure and composition of the Earth's crust. Over continental areas, magnetic anomalies illuminate geologic, tectonic, and geothermal evolution of crust and lithosphere. In the world's oceans, anomalies trending parallel to the isochrons (lines of equal age) reveal the temporal evolution of oceanic crust. Magnetic maps are widely used in the geological sciences and in resource exploration.
Use Limitations
  • Produced by the NOAA National Centers for Environmental Information. Not subject to copyright protection within the United States.
  • Not to be used for navigation. Although these data are of high quality and useful for planning and modeling purposes, they are not suitable for navigation. For navigation, please refer to the NOS nautical chart series.
Dataset Citation
  • Cite as: Brian Meyer; Richard Saltus; and Arnaud Chulliat. 2017: EMAG2v3: Earth Magnetic Anomaly Grid (2-arc-minute resolution). Version 3. NOAA National Centers for Environmental Information. https://doi.org/10.7289/V5H70CVX. Accessed [date].
Cited Authors
  • Brian Meyer
  • Richard Saltus
  • Arnaud Chulliat
Originators
  • NCEI Geomagnetic Modeling Team
Publishers
  • NOAA National Centers for Environmental Information
Theme keywords Global Change Master Directory (GCMD) Science Keywords
  • Earth Science > Solid Earth > Geomagnetism > Magnetic Field
  • Earth Science > Solid Earth > Geomagnetism > Magnetic Intensity
  • Earth Science > Solid Earth > Geomagnetism > Magnetic Anomalies
Data Center keywords Global Change Master Directory (GCMD) Data Center Keywords
  • DOC/NOAA/NESDIS/NCEI > National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce
  • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
Place keywords Global Change Master Directory (GCMD) Location Keywords
  • Geographic Region > Global
Use Constraints
  • Use liability: NOAA and NCEI cannot provide any warranty as to the accuracy, reliability, or completeness of furnished data. Users assume responsibility to determine the usability of these data. The user is responsible for the results of any application of this data for other than its intended purpose.
Access Constraints
  • Distribution liability: NOAA and NCEI make no warranty, expressed or implied, regarding these data, nor does the fact of distribution constitute such a warranty. NOAA and NCEI cannot assume liability for any damages caused by any errors or omissions in these data. If appropriate, NCEI can only certify that the data it distributes are an authentic copy of the records that were accepted for inclusion in the NCEI archives.
Other Constraints Cite as: Brian Meyer; Richard Saltus; and Arnaud Chulliat. 2017: EMAG2v3: Earth Magnetic Anomaly Grid (2-arc-minute resolution). Version 3. NOAA National Centers for Environmental Information. https://doi.org/10.7289/V5H70CVX. Accessed [date].
Fees
  • In most cases, electronic downloads of the data are free. However, fees may apply for custom orders, data certifications, copies of analog materials, and data distribution on physical media.
Lineage information for: model
Processing Steps
  • Trackline data selection. Data needed to report date/time of collection, total observed magnetic field, collected during time where kp < 6o.
  • From all original ship and airborne measurements: subtracted main and external fields given by the Comprehensive Model 4(Sabaka et al., 2004)
  • Airborne data downward continued to sea-level
  • Gridded trackline data using a krigging algorithm. Smoothing was applied where necessary.
  • Precompiled grids had wavelengths greather than 300km replaced with values from MF7.
Lineage information for: repository
Processing Steps
  • 2015-04-22T00:00:00 - NOAA created the National Centers for Environmental Information (NCEI) by merging NOAA's National Climatic Data Center (NCDC), National Geophysical Data Center (NGDC), and National Oceanographic Data Center (NODC), including the National Coastal Data Development Center (NCDDC), per the Consolidated and Further Continuing Appropriations Act, 2015, Public Law 113-235. NCEI launched publicly on April 22, 2015.
Last Modified: 2020-05-14
For questions about the information on this page, please email: ncei.info@noaa.gov