Draping corrections for aeromagnetic data: line-versus grid-based approaches

Abstract

In drape-flown aeromagnetic surveys, operational factors such as weather and rugged ground topography may result in certain lines flown at average heights significantly different from the nominal terrain clearance. Such changes in the distance from sensor to magnetic source lead to variable attenuation of the magnetic field and result in spurious anomalies oriented along flight lines. A recent survey flown in Namibia was subjected to high wind conditions that led to some anomalously high flight lines and severe corrugation effects in the gridded data parallel to the line direction. Computational draping of the measured field to correct for the line-height variation was carried out on both gridded and line data using a Taylor series approach. The line-based approach produced the best results. Gradients calculated from the gridded data (perpendicular to the traverse lines) were overwhelmed by errors caused by the large line-to-line height variation.