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.
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2010. National Geophysical Data Center. This line shapefile shows lines of equal annual change (secular variation), in the total field intensity of the Earth's magnetic field, derived fro... National Atlas of the United States.
2010. National Geophysical Data Center. This line shapefile shows lines of equal annual change (secular variation) in the vertical component of the total field intensity of the Earth's ma... 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. National Geophysical Data Center. This line shapefile shows lines of equal vertical intensity of the Earth's magnetic field, derived from the International Geomagnetic Reference Fie... National Atlas of the United States.
1999. Geological Survey (U.S.). This line shapefile portrays the major roads in the United States, Puerto Rico, and the U.S. Virgin Islands. The file was produced by joining the i... Geological Survey (U.S.).
2011. United States. Office of the Deputy Under Secretary of Defense (Installations and Environment) and United States. Bureau of Transportation Statistics. This polygon shapefile depicts sites that were selected from the 2010 Base Structure Report (BSR), a summary of the DoD Real Property Inventory (RP... United States. Bureau of Transportation Statistics.
2011. Lubkin, Samantha, Blades, Doug, United States. Federal Highway Administration, and United States. Bureau of Transportation Statistics. This point shapefile depicts the more than 600,000 of the United States' bridges located on public roads, including interstate highways, United Sta... United States. Bureau of Transportation Statistics.
2004. National Atlas of the United States. This polygon shapefile portrays county level data for the fiscal-year-2004 National Fire Plan - Hazardous Fuels Reduction Program. The purpose of t... National Atlas of the United States.
1972. National Atlas of the United States. This polygon shapefile contains National Wilderness Preservation System areas of 640 acres or more, in the United States, Puerto Rico, and the U.S.... National Atlas of the United States.
