Photo: Gerhard Schwarz, SGU

Geomagnetic documentation

SGU measures and documents how the Earth’s magnetic field varies in time and space and makes forecasts about changes in the field.

Mankind has used Earth’s magnetic field to navigate since the first compasses were constructed in China around a thousand years ago. The magnetic field works like an umbrella, a protective sheet, against solar wind and -storms. This radiation of hard particles is also the source of spectacular light phenomenon in the sky, called northern lights and southern lights.

Sweden has three observatories that continuously record variations in the geomagnetic field. The stations are located west of Uppsala (UPS), in Abisko (ABK) and in Lycksele (LYC, operated in cooperation with the Swedish Institute of Space Physics). Data are reported in nearly real-time to international datacenters, such as Intermagnet and World Data Center C2. Continuous observations of the magnetic field have been done since the 1920s and by SGU since 1969.

SGU also produces maps that show the spatial variation of the magnetic field’s strength and direction in all over Sweden. Mapping is primarily based on repeated measurements in a nationwide network, as well as data from a comprehensive airborne survey done at 3 km altitude in 1965. This mapping has, among others, the purpose to provide information on magnetic  declination, i.e., the difference between compass and true North. Earth’s magnetic field changes continuously over time and therefore declination data must be updated regularly. This information is used widely by community stakeholders, e.g., the military forces, the Maritime Administration (Sjöfartsverket), the Civil Aviation Administration (Luftfartsverket) and the National Land Survey (Lantmäteriet).

Geomagnetic data are also used in research as well as in various geophysical and geological operations - both nationally and internationally. Demand for geomagnetic information has increased in line with the general trend in technology and electronics in recent decades.

SGU offers surveys of Earth's magnetic total field or its components at local or regional level. We have great experience of determining both magnetic and geographical North (magnetic declination). UPS observatory is also used in connection with the development and calibration of magnetic instruments.

Compass declination 2021 in the Nordic countries

The map shows the deviation between compass and true North. The curves (isogons) in the map unites localities with the same declination. Positive declination is counted towards the east. Observe that local variations may occur.

Download the map in high resolution PDF (new window)


Last reviewed 2021-03-18