Global geomagnetic observatory annual means.

Annual means of the geomagnetic field vector components from observatories around the world, from 1840 to the present day. At present there are about 160 observatories. These data are useful for tracking changes in the magnetic field generated inside the Earth. Data are produced by a number of organisations around the world, including BGS. Data are available in plain text from www.geomag.bgs.ac.uk. This data is connected to other geomagnetic data sets, but can be used without reference to them.