You searched for: Author National Geophysical Data Center Remove constraint Author: National Geophysical Data Center Subject Geoscientific Information Remove constraint Subject: Geoscientific Information Subject Magnetic declination Remove constraint Subject: Magnetic declination Place Massachusetts Remove constraint Place: Massachusetts Place United States Remove constraint Place: United States Format Shapefile Remove constraint Format: Shapefile
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.
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.