Magnetic observatory data and metadata : types and availability

The availability of magnetic observatory data has evolved rapidly with the transition of observatories from analogue photographic magnetograms to digital electronic recordings, and the advent of the internet for instant global access to information of every sort. Metadata (information about the data) is undergoing its own transformation in order to accompany the rapid and extensive dissemination of these data. This chapter describes the types of data historically and currently produced by geomagnetic observatories and introduces new data types such as one-second and quasi-absolute data recently discussed at the 11th IAGA Scientific Assembly in Sopron, Hungary.We review the availability of these data types from the World Data Centres, INTERMAGNET and other sources. Finally, we discuss developments in metadata describing the current efforts in the geomagnetism community to gather, store and distribute this information about the data to better assist scientific discovery.