Geomagnetism

EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution)

Print map (paper and digital download) of EMAG2 available at BGR Geoshop

GIS GeoTIFF versions of EMAG2 included in the product table at the bottom of this page

Magnetic anomaly maps provide insight into the subsurface structure and composition of the Earth's crust. Anomalies trending parallel to the isochrons (lines of equal age) in the oceans reveal the temporal evolution of oceanic crust. Magnetic maps are widely used in the geological sciences and in resource exploration. Furthermore, the global magnetic map is useful in science education to illustrate various aspects of Earth evolution such as plate tectonics and crustal interaction with the deep mantle. Distinct patterns and magnetic signatures can be attributed to the formation (seafloor spreading) and destruction (subduction zones) of oceanic crust, the formation of continental crust by accretion of various terranes to cratonic areas and large scale volcanism (both on continents and oceans).

EMAG2 is a significant update over our first global magnetic anomaly grid, EMAG3, which provided the base grid for the World Digital Magnetic Anomaly Map of the Commission of the World Geological Map. As reflected in the name the resolution has been improved from 3 arc minute to 2 arc minute and the altitude has been reduced from 5 km to 4 km above geoid. Additional grid and trackline data have been included, both over land and the oceans. Interpolation between sparse tracklines in the oceans was improved by directional gridding and extrapolation, based on an oceanic crustal age model . The longest wavelengths (larger than 330 km) were replaced with the latest CHAMP lithospheric field model MF6.

Fig.1: (click to enlarge) EMAG2 looking north-west at Portugal/Spain from the Atlantic. Kursk (Russia) is seen as a strong anomaly in the background. The stripes on the left of the image are magnetic lineations due to sea-floor spreading. Plug-in files for NASA World Wind can be downloaded from GETECH .

EMAG2 is specified as a global 2-arc-minute resolution grid of the anomaly of the magnetic intensity at an altitude of 4 km above mean sea level. It was compiled from satellite, marine, aeromagnetic and ground magnetic surveys (see our acknowledgment of data providers and collaborators). A version for visualization in NASA World Wind can be downloaded from GETECH . See also the implementations for EMAG2 in Google Earth and EMAG2 in Google Maps.

EMAG2 is also available as a print map (on paper or to self-print from PDF) from the German Federal Institute for Geosciences and Natural Resources (BGR). To order/download the map please visit the BGR Geoshop.

Metadata for the EMAG2

Available EMAG2 Downloads
	Type	Format	Mbyte	Contents
	Full resolution map	PDF	160	EMAG2 as a poster (Version 2.0)
	Full resolution map	JPG	160	EMAG2 as a poster (Version 2.0)
	Full resolution map	JPG	145	EMAG2 as an image (Version 2.0)
	Article	PDF	10	Preprint of manuscript EMAG2: A 2-arc-minute resolution Earth Magnetic Anomaly Grid compiled from satellite, airborne and marine magnetic measurements, submitted for publication to Geochem. Geophys. Geosyst.
	Google Earth	KMZ	0.1	Plugin for Google Earth. Requires installation of Google Earth. See also the related Google Earth Community Forum posting
	xyz/zip	zipped ascii	442	EMAG2 (Version 2.0) ASCII grid of the magnetic total intensity at 4km above WGS84 ellipsoid
	GIS tif	GeoTIFF	228	A georeferenced TIFF (GeoTIFF) 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. The nodata value is -99999.
	GMT grd	NETCDF	228	A GMT (Generic Mapping Tools) compatible netCDF grid with resolution of 2 arc-minutes. The values (nT) are stored as 32-bit floating point. The nodata value is -99999.
	Color-relief	GeoTIFF	132	A 24-bit RGB georeferenced TIFF (GeoTIFF) color-relief visualization of the EMAG2 grid, which can be opened by ArcGIS or any other GIS application. The color scale legend is in EMAG2_scale.png.
	xyz/zip	zipped text	225	EMAG2 (Version 2.0) ASCII grid of the magnetic total intensity at 4km above WGS84 ellipsoid. This version was produced without directional gridding. Therefore, it has much sparser coverage but reflects more closely the actual measurements.

Stefan Maus