The non-magnetic

theodolites Zeiss THEO 010 and THEO 020

Jürgen Matzka (1), Thomas Wenger (2), Jörg Krüger (2),

Achim Morschhauser (1), Carsten Müller-Brettschneider


(1) GFZ German

Research Centre for Geosciences, Potsdam, Germany, (2)

Wenger-Wiethüchter Vermessungstechnik, Jena,



The non-magnetic theodolites Zeiss THEO 010

and THEO 020 fitted with a fluxgate magnetometer is the predominant

absolute instrument for measurements of the direction of the

geomagnetic field in observatories and repeat stations. The

instruments, all of them being tens of years old by now, will be

crucial for the observation of the Earth's magnetic field for many

years to come. In this contribution, we concentrate on the

theodolite, which is the basis of the instrument. We look at its

history, with special emphasis on the non-magnetic versions, and we

discuss ways how they can be tested at geomagnetic observatories. We

also look at tests, maintenance and repair work that can be performed

in specialised workshops. Finally, we aim at giving an outlook on the

future of these instruments.