Magnetic interference testing method for an electric fixed-wing unmanned aircraft system (UAS)

One of the barriers preventing unmanned aircraft systems (UASs) from having a larger presence in the geophysical magnetic surveying industry is the magnetic interference generated by the UAS and its impact on the quality of the recorded data. Detailed characterization of interference effects is therefore needed before remedial solutions can be proposed. A method for characterizing magnetic interference is demonstrated for a 21 kg, 3.7 m wingspan, 6 kW electric fixed-wing UAS purposely built for magnetic surveying. It involves mapping the spatial variations of the total magnetic intensity resulting from the interference sources on the UAS. Dynamic tests showed that the motor should be engaged and the aircraft control surfaces levelled prior to mapping. Experimental results reveal that the two strongest sources of magnetic interference are the cables connecting the motor to the batteries, and the servos. Combining three factors to assess the level of magnetic interference — the total magnetic intensity, 4th difference and vertical magnetic gradient — an index overlay shows that the magnetic sensor(s) should be located at least 50 cm away from the wingtips or tail to ensure an interference level of <2 nT, a 4th difference of <0.05 nT, and a gradient of <10 nT/m.