This study demonstrates the practical feasibility of high-precision in-flight measurement of magnetic fields from remote radio transmitters, including the use of unmanned aerial vehicles. The proposed method is based on calculating the Euclidean norm of the full complex magnetic field vector, which eliminates any dependence of the result on the orientation of the measurement system. To compensate for primary field instability, normalization is performed using a synchronized signal from a stationary base receiver. Further accuracy is achieved through pre-flight sensor calibration and spatial data smoothing during processing. Test measurements demonstrate good result reproducibility, with a discrepancy of less than 0.5% of the signal level. Moreover, magnetic field anomaly maps obtained at different altitudes show strong correlation both with each other and with archival data from ground-based inductive electromagnetic surveys.
Epishkin et al. (Mon,) studied this question.