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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 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.
2002, 2003, and 2004. Geological Survey (U.S.). This point shapefile portrays major dams of the United States, including Puerto Rico and the U.S. Virgin Islands. The map layer was created by extr... Geological Survey (U.S.).
2006. Rawson, Peg. This point shapefile depicts major dams in the United States, including Puerto Rico and the U.S. Virgin Islands. The map layer was created by extra... United States. Bureau of Transportation Statistics.
1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, and 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.).
2010. United States. Department of Commerce, United States. National Oceanic and Atmospheric Administration, and United States. National Ocean Service. a standardized compilation of published marine boundaries from the NOAA Office of Coast Survey and the Minerals Management Service. Authoritative m... United States. National Ocean Service.
2012. I.M. Systems Group. This polygon shapefile represents the geographic location and identity of designated areas used to manage vessel traffic in the northeast United St... United States. National Oceanic and Atmospheric Administration.