Publications

South Africa Geomagnetic repeat station surveys have a long tradition of supplementing secular variation information provided by permanent magnetic observatories. Measurements at individual repeat stations are normally conducted over a period lasting between one and a few days within a year. It is a much more difficult task to separate information about the individual internal and external field contributions from repeat station data than it is from the continuous recordings of an observatory. In general, repeat station data are processed in a way to eliminate all external contributions from the measurements as best as possible in order to utilize the data in main field and secular variation modeling, mostly at the regional scale. Variometers deployed nearby can be used to eliminate most of the external fields with periods shorter than the deployment time of the variometer. However, permanent magnetic observatory recordings are mostly used, additionally to temporary variometers or solely, in order to derive comparable values from a network of repeat stations for one common date. Consequently such data are never truly independent. We discuss the accuracy that can be expected from repeat station data based on our experience with measurements in Germany, in the framework of the European MagNetE (Magnetic Network of Europe) initiative, and in southern Africa, a cooperation within the Inkaba yeAfrica project. We present different applications of repeat station data in areas with dense and sparse observatory coverage, respectively, and show how repeat station surveys are still useful in the era of longterm magnetic satellite missions.

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Korte, M.; Mandea, M.; Kotzé, P. (2008): Utility and accuracy of geomagnetic repeat station surveys. 13th IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing (Golden and Boulder, Colorado 2008).