Magnetic Field - Secular Variation of the Declination Component for the Epoch 2010.0

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Abstract/Contents

Abstract: This map layer shows isoporic lines (lines of equal annual change, or secular variation, in the declination of the Earth's magnetic field), derived from the International Geomagnetic Reference Field (IGRF) for the epoch 2010.0. Magnetic declination is the angle between true north and magnetic north (the direction of the magnetic field vector) in the horizontal plane. The change is measured in arc minutes per year. This layer is part of the 1997-2014 edition National Atlas of the United States.
Purpose: These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the National Atlas of the United States or the U.S. Geological Survey in the use of these data.

Type of resource	cartographic, software, multimedia
Form	Shapefile
Extent	4.674
Place	Reston, Virginia, US
Publisher	National Atlas of the United States
Publication date	2011
Language	English
Digital origin	born digital
Map data	Scale not given. ; EPSG::4269 W 179°49ʹ45ʺ--E 179°12ʹ9ʺ/N 86°26ʹ--N 3°22ʹ19ʺ, Scale not given ; EPSG::4326

Creator	National Geophysical Data Center

Subject	Geomagnetism
Subject	Magnetic declination
Subject	Geomagnetism > Secular variations
Subject	United States
Subject	Alaska
Subject	Alabama
Subject	Arizona
Subject	Arkansas
Subject	Colorado
Subject	Connecticut
Subject	Delaware
Subject	Florida
Subject	Georgia
Subject	Hawaii
Subject	Idaho
Subject	Illinois
Subject	Indiana
Subject	Iowa
Subject	Kansas
Subject	Kentucky
Subject	Louisiana
Subject	Maine
Subject	Maryland
Subject	Massachusetts
Subject	Michigan
Subject	Minnesota
Subject	Mississippi
Subject	Missouri
Subject	Montana
Subject	Nebraska
Subject	Nevada
Subject	New Hampshire
Subject	New Jersey
Subject	New Mexico
Subject	New York (State)
Subject	North Carolina
Subject	North Dakota
Subject	Ohio
Subject	Oklahoma
Subject	Oregon
Subject	Pennsylvania
Subject	Rhode Island
Subject	South Carolina
Subject	South Dakota
Subject	Tennessee
Subject	Texas
Subject	Utah
Subject	Vermont
Subject	Virginia
Subject	Washington (D.C.)
Subject	Washington (State)
Subject	West Virginia
Subject	Wisconsin
Subject	Wyoming
Subject	Puerto Rico
Subject	United States Virgin Islands
Subject	Cuba
Subject	North America
Subject	Mexico
Subject	Canada
Subject	2010
Subject	Geoscientific Information
Genre	Geospatial data
Genre	Cartographic dataset

Supplemental information	The declination component (D) and the secular variation (DSV, the time rate of change of D) of the IGRF change smoothly over most of the Earth with the exception of a region surrounding each of the geomagnetic poles. Near the geomagnetic poles, the isogonic lines (lines of constant declination) and isoporic lines crowd closer and closer together because at adjacent grid points (1 degree separation) the IGRF values of D and DSV upon which the lines are based vary extremely. For more information about the geomagnetic field, please visit <http://www.ngdc.noaa.gov/geomag/faqgeom.shtml.>
WGS84 Cartographics	This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.
Location	https://purl.stanford.edu/hc347kh4279

Use and reproduction: This item is in the public domain. There are no restrictions on use.
Copyright: This work is in the Public Domain, meaning that it is not subject to copyright.

Preferred citation: National Atlas of the United States. (2011). Magnetic Field - Secular Variation of the Declination Component for the Epoch 2010.0. National Atlas of the United States. Available at: http://purl.stanford.edu/hc347kh4279.

National atlas of the United States of America, 1997-2014

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