  Over the southern African region the geomagnetic field is weak and changes
rapidly. For this area series of geomagnetic field measurements exist since the
1950s. We take advantage of the existing repeat station surveys and observatory
annual means, and clean these data sets by eliminating jumps and minimising
external field contributions in the original time series. This unique data set
allows us to obtain a detailed view of the geomagnetic field behaviour in space
and time by computing a regional model. For this, we use a system of
representation similar to harmonic splines. Initially, the technique is
systematically tested on synthetic data. After systematically testing the
method on synthetic data, we derive a model for 1961 to 2001 that gives a
detailed view of the fast changes of the geomagnetic field in this region.
