A comparison of the inductive-limit footprints of airborne electromagnetic configurations

An inductive-limit model has been used to determine footprint sizes for a variety of common airborne electromagnetic-survey geometries. The model accounts both for variations in the height and orientation of the electromagnetic transmitter, and for electromagnetic coupling between the induced current system and the receiver. Horizontal magnetic-dipole transmitters are shown to have a smaller footprint than vertical magnetic-dipole sources. We show that footprint sizes for the vertical coaxial and vertical coplanar geometries are essentially identical, provided the transmitter-receiver separation is much less than the transmitter height. The inductive-limit horizontal-component footprint for a fixed-wing horizontal-loop transmitter with a towed-bird receiver is shown to be two-thirds of that for the vertical component.