An improved technique for reduction to the pole at low latitudes

Reduction to the pole at low latitudes based on a Wiener filtering approach has been improved by introducing a deterministic noise model. It is assumed that the noise power is a fixed fraction of the signal power. This allows the method to be fully automated. Further improvement is obtained by requiring the reduced-to-the-pole field to map into the observed field when projected to the geomagnetic latitude of the observed field. This is done by iteratively minimizing the difference between the measured field and the reduced-to-the-pole field projected to the geomagnetic latitude of the measured data. This results in a reduced-to-the-pole magnetic map that, when projected to the geomagnetic latitude of the given data, closely matches the measured data. The final reduced-to-the-pole field does not show any of the artifacts typical of reduction-to-the-pole at low geomagnetic latitudes. The method is demonstrated on a data set from an aeromagnetic survey flown over north-central Burkina Faso, West Africa.