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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.
2004. Instituto Nacional de Estadística, Geografía e Informática (Mexico), Canada Centre for Mapping, and Geological Survey (U.S.). This line shapefile shows bathymetric contours with depth in metres for ocean areas covered by the extent of the North American Atlas project. Isob... Canada Centre for Mapping, Instituto Nacional de Estadística, Geografía e Informática (Mexico), and Geological Survey (U.S.).
2004. California. Department of Fish and Game. Marine Resources Region. This line shapefile represents the offshore boundary between the United States and Mexico. This layer is part of a collection of data created by th... California. Department of Fish and Game. Marine Resources Region.
2004. Instituto Nacional de Estadística, Geografía e Informática (Mexico), Geological Survey (U.S.), and Canada Centre for Remote Sensing. This line shapefile depicts the political boundaries of North America, including: international boundaries, provincial boundaries, state or territo... Geological Survey (U.S.).
2004. Instituto Nacional de Estadística, Geografía e Informática (Mexico), Geological Survey (U.S.), and Canada Centre for Remote Sensing. This line shapefile represents roads in North America at 1:1,000,000 scale. The roads included in this layer are either those that connect major ce... Geological Survey (U.S.).