2010. National Geophysical Data Center. This map layer shows isogonic lines (lines of constant declination of the Earth's magnetic field), derived from the International Geomagnetic Refer... National Atlas of the United States.
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2010. National Geophysical Data Center. This line shapefile shows lines of equal horizontal intensity of the Earth's magnetic field, derived from the International Geomagnetic Reference F... National Atlas of the United States.
2010. National Geophysical Data Center. This shapefile shows isoclinic lines (lines of constant inclination of the Earth's magnetic field), derived from the International Geomagnetic Refe... National Atlas of the United States.
2010. National Geophysical Data Center. This map layer shows isoporic lines (lines of equal annual change, or secular variation, in the declination of the Earth's magnetic field), derived... National Atlas of the United States.
2010. National Geophysical Data Center. This line shapefile shows lines of equal annual change (secular variation) in the horizontal component of the total field intensity of the Earth's ... National Atlas of the United States.
2010. National Geophysical Data Center. This shapefile shows lines of equal annual change (secular variation) in the inclination of the Earth's magnetic field, derived from the Internatio... National Atlas of the United States.
2010. National Geophysical Data Center. This shapefile contains isodynamic lines (lines of equal total intensity of the Earth's magnetic field), derived from the International Geomagnetic... National Atlas of the United States.
2010. United States. Office of Ocean and Coastal Resource Management, National Marine Protected Areas Center (U.S.), United States. Department of Commerce, and United States. National Oceanic and Atmospheric Administration. This polygon shapefile represents the Marine Protected Areas inventory as of March 2010. The MPA Inventory is a comprehensive geospatial database t... National Marine Protected Areas Center (U.S.).