Definitive digital values of the Earth's magnetic field recorded during 1991 to 2020 at INTERMAGNET observatories around the world. Data includes minute, hourly and daily vector values, along with observatory baseline values for quality control. Annual means are also included, as are K indices, which quantify disturbance levels at each observatory.. All data are included on the downloadable archive files. This is the 30th annual publication in the series. Some national data institutions may have related DOIs that describe subsets of the data. These DOIs are shown under "Related DOIs to be quoted".

For more information on the data formats used in this publication and the technical standards used to create the data, please refer to the INTERMAGNET Technical Manual (https://doi.org/10.48440/INTERMAGNET.2020.001).

Geomagnetic data is recorded and quality controlled at the institutions responsible for each observatory. Before becoming a member of INTERMAGNET, institutes must make a detailed submission for each observatory that is to join. This submission is verified by a committee in INTERMAGNET before the observatory is admitted. Only data from INTERMAGNET members is published by INTERMAGNET. Each annual definitive data set is checked for quality by a team of data checkers in INTERMAGNET before the data is admitted to the series for that year.

The International Real-time Magnetic Observatory Network (INTERMAGNET) is the global network of observatories, monitoring the Earth's magnetic field. The INTERMAGNET programme exists to establish a global network of cooperating digital magnetic observatories, adopting modern standard specifications for measuring and recording equipment, in order to facilitate data exchange and the production of geomagnetic products in close to real time. INTERMAGNET also coordinates the publication of quality-controlled, definitive geomagnetic data from its affiliated observatories.