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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 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 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.
2009. World Wildlife Fund. This river network (stream lines) map for North America is derived from the flow direction map for North America. The flow accumulation map for Nor... Geological Survey (U.S.).
2009. World Wildlife Fund. This river network (stream lines) map for North America is derived from the flow direction map for North America. The flow accumulation map for Nor... Geological Survey (U.S.).
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. Instituto Nacional de Estadística, Geografía e Informática (Mexico), Canada Centre for Mapping, and Geological Survey (U.S.). This polygon shapefile contains bathymetric data with depth in metres for ocean areas covered by the extent of the North American Atlas project. Is... Canada Centre for Mapping, Instituto Nacional de Estadística, Geografía e Informática (Mexico), and Geological Survey (U.S.).
1830, 1831, 1832, 1833, 1834, 1835, 1836, 1837, 1838, 1839, 1840, 1841, 1842, 1843, 1844, 1845, 1846, 1847, 1848, 1849, 1850, 1851, 1852, 1853, 1854, 1855, 1856, 1857, 1858, 1859, 1860, 1861, 1862, 1863, 1864, 1865, 1866, 1867, 1868, 1869, 1870, 1871, 1872, 1873, 1874, 1875, 1876, 1877, 1878, 1879, 1880, 1881, 1882, 1883, 1884, 1885, 1886, 1887, 1888, 1889, 1890, 1891, 1892, 1893, 1894, 1895, 1896, 1897, 1898, 1899, 1900, 1901, 1902, 1903, 1904, 1905, 1906, 1907, 1908, 1909, 1910, 1911, 1912, 1913, 1914, 1915, 1916, 1917, 1918, 1919, 1920, 1921, 1922, 1923, 1924, 1925, 1926, 1927, 1928, 1929, 1930, 1931, 1932, 1933, 1934, 1935, 1936, 1937, 1938, 1939, 1940, 1941, 1942, 1943, 1944, 1945, 1946, 1947, 1948, 1949, 1950, 1951, 1952, 1953, 1954, 1955, 1956, 1957, 1958, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970, 1971, 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, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, and 2008. National Atlas of the United States. This poygon shapefile portrays the distributions of United States and Canadian bat species during the past 100-150 years (1830-2009). The specimen ... National Atlas of the United States.