Guidelines for location and use of base station data in aeromagnetic survey processing

Observations have indicated that temporal variations in the magnitude of the geomagnetic field can show a significant decrease in correlation at distances larger than 200 km. We confirm this by a study of geomagnetic measurements from a magneto-telluric survey in Alberta, Canada. Using these data, we estimate the coherence of the total-field magnetic signal between pairs of stations as a function of distance. The measurements are from two profiles, one where a strong conductor is present at depth and one where the conductivity is laterally uniform over the penetration depth of the signals. The coherence decreases at short periods and with increasing distance between the stations. Different coherence behavior is observed for the two profiles. This is attributed to the differences in the geo-electric sections. These results are used to propose improved guidelines for the use of base-station measurements in aeromagnetic data processing. © 2005 Society of Exploration Geophysicists.