Due to the global nature of the geomagnetic field and the pervasive use of magnetic sensing devices in the global navigational infrastructure, the maintenance of magnetic models, charts and maps is both a national and an international concern.
Magnetic charts show the elements of the Earth's magnetic field and their annual change.
The U.S. Geological Survey produces magnetic charts for the United States and the world. The Magnetic Observatory system has a relatively short history dating back to the early 1800's. The need for accurate and continuous measurements of the Earth's magnetic field was recognized early in the field of geomagnetism, both for historical database archives, and for studies of the Sun, the Earth's interior, and the surrounding space environment. You are free to use this package as much as you wish and are free to distribute it as long as you do not charge for distribution and as long as it is distributed in its entirety. The progam is avaiable in both DOS and Windows 95 versions.