What follows is very detailed technical information about this map layer. This is often called metadata. Metadata are used to organize and maintain investments in data, to provide information to data catalogs and clearinghouses, and to aid data transfers. Many organizations within and outside of the federal government have adopted the FGDC metadata standard and are using automated indexing and serving mechanisms to provide access to their holdings through the Internet. Visit the FGDC Clearinghouse to learn more about how metadata is used in clearinghouses and to search for other data sets.
Magnetic inclination is the angle between the magnetic field vector and the horizontal plane.
The change is measured in arc minutes per year. No responsibility is assumed by the U.S. Geological Survey in the use of these data. No explicit attempt was employed to judge the accuracy of the lines with respect to the source gridded data. However, visual examination revealed that the lines portrayed are continuous and non-intersecting. This data set shows lines of constant secular variation of inclination for all of North America, including Greenland, Iceland, the Caribbean and most of Mexico.