Geophysical Methods Applied To Mining At Ultra-Depth: First Resuits Of The Deepmine Programme

One of the major problems in aeromagnetic data processing is the elimination of the effects of time dependent external magnetic field variations (daily variation, magnetic storms and ULF pulsations) from the aircraft survey data. Not only do these phenomena contaminate the survey data, but magnetic storms may also result in unproductive time while the aircraft is kept on the ground during the active phase of these storms. The use of data from a fixed base station has distinct problems. Accurate time synchronisation between the aircraft and base station<br>recordings is usually required and direct subtraction of the base station data from the aircraft data can in fact result in further deterioration of the aircraft data - e.g. if the base station is located on a conductivity anomaly its recordings may suffer frequency dependent phase shifts and amplitude changes.