Surface loop monitoring of airborne electromagnetic systems
James C. Macnae, Aaron Davis · 2004
As part of AMIRA Project P407b, we are studying methods for the calibration of airborne electromagnetic (AEM) systems. One very simple method proposed involves laying out a closed calibration-loop of wire on resistive ground, and measuring the current induced in it as an AEM system flies overhead. The measured calibration-loop currents can theoretically be used as a check on 1) transmitter waveform; 2) system geometry (including altimetry and flight-path recovery); 3) receiver geometry relative to the transmitter; and 4) overall system linearity and phase/timing. A more complex situation is predicted to occur in practice since the calibration-loop will usually need to be placed on conductive rather than resistive ground. In this case, currents induced in the ground by the AEM system are coupled into the calibration loop, and the AEM receiver detects responses from all of the transmitter, ground and calibration-loop. This paper presents an analysis of initial experiments monitoring current in a calibration-loop with overflight of a Geotem AEM system.