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 NOAA > NESDIS > NCEI (formerly NGDC) > Geomagnetism

Models are joint research with:
The Cooperative Institute for Research in Environmental Sciences (CIRES).

How to cite EMAG2v3 data: doi:10.7289/V5H70CVX

EMAG2v3: Earth Magnetic Anomaly Grid at 2-arc-minute Resolution, Version 3

EMAG2v3 is compiled from satellite, ship, and airborne magnetic measurements. Magnetic anomalies result from geologic features enhancing or depressing the local magnetic field. These maps increase knowledge of subsurface structure and composition of the Earth's crust. Global magnetic anomaly grids are used for resource exploration, navigation where GPS is unavailable (submarine, directional drilling, etc.), and for studying the evolution of the lithosphere.

The 2017 release of the EMAG2v3 utilizes updated precompiled grids and a revised process for accurately incorporating the long-wavelength anomalies, as modeled by the satellite-based MF7 lithospheric field model. It is an update from the previous EMAG2v3 released by NCEI in 2016. EMAG2v3 further differs from the previous EMAG2 (version 2, see link at the bottom of this page), which relied on an ocean age model to interpolate anomalies into non-existent data areas and on the earlier MF6 model. EMAG2v3 relies solely on the data available. As a result, EMAG2v3 better represents the complexity of these anomalies in oceanic regions and accurately reflects areas where no data has been collected. The current version reports anomalies in two ways:

  1. A consistent altitude of 4 km (referred to as Upward Continued)
  2. Anomaly altitude at Sea Level


Title Type Download / Link Size Description
EMAG2v3 Source ASCII CSV Data Format 4.5 GB EMAG2_V3_20170530 is delivered as a 1.5GB zip file that contains comma delimited data (CSV). The format descriptor is a text file that provides information about the CSV file.
EMAG2v3 Source GeoTIFFs GeoTIFF* Upward Continued Sea Level 228 MB Values (nT) are stored as 32-bit floating point. The nodata value is 99999.
Color Hillshade Image GeoTIFF* Upward Continued Sea Level 86 MB A color relief image rendered with a "hillshade" effect to simulate a 3D surface (see: color scale legend). The format is 24-bit RGB GeoTIFF*.
EMAG2v3 Map PNG Upward Continued Sea Level 61 MB Maps contain both mercator and polar stereographic projections.
Google Earth Image KMZ Upward Continued 125 MB Upward Continued grid with data gaps filled by MF7. KMZ file can be used with the Google Earth application.
ISO Metadata XML Metadata Includes data citation information, lineage, etc.
Color-relief Image GeoTIFF* Upward Continued Sea Level 158 MB A 24-bit RGB GeoTIFF* color-relief visualization of the EMAG2v3 grid.
Supplemental Information PNG Code Map Error Map 33 MB The Code Map provides a reference to the primary data source for each cell as described in the Format file above. The Error Map displays the error associated with each grid cell.
Supplemental Information GeoTIFF* Data Source Code Error Estimate 228 MB Values are stored as 16-bit integers. See the above table for the data source code. The error estimate is in nT.

* Georeferenced TIFF (GeoTIFF) format can be used in Esri ArcGIS or any other GIS application.

EMAG2 (version 2)

This version (2009) is a significant update over our first global magnetic anomaly grid, EMAG3. It relies on ocean age models to directionally grid anomaly data into areas where no data exists. The grid is reported at an altitude of 4 km.

EMAG3

This version (2007) is a 3 arc-minute resolution magnetic anomaly map. It was the NGDC (now NCEI) candidate for the World Digital Magnetic Anomaly Map at 5 km altitude.

Global animation

The global magnetic map illustrates Earth evolution (plate tectonics and crustal interaction with the deep mantle).

Distinct patterns and magnetic signatures are attributed to the formation (seafloor spreading) and destruction (subduction zones) of oceanic crust, and the formation of continental crust by accretion of various terrains to cratonic areas and large scale volcanism (both on continents and oceans).

  • Magnetization is weaker at the equator and stronger at high latitudes, reflecting the strength of the ambient geomagnetic field, which induces magnetization in rocks

  • Stripes of alternating magnetization in the oceans are due to sea floor spreading and the alternating polarity of the geomagnetic field

  • Very old crust (North American Shield, Baltic Shield, Siberian Craton) have strongest magnetization, seen as dark shades of purple and blue