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.
Two methods for low‐altitude calibration of a single‐rotor unmanned aircraft system using a real‐time compensator are tested: (1) a stationary calibration where the unmanned aircraft system executes manoeuvres while hovering in order to minimize ambient field changes due to the local geology; and (2) an adapted box calibration flown in four orthogonal directions. Both methods use two compensator‐specific limits derived from established methods for manned airborne calibration: the lowest frequency used by the compensator for the calibration algorithm and the maximum variation of the ambient magnetic intensity experienced by the unmanned aircraft system during calibration. Prior to flying, the unmanned aircraft system was magnetically characterized using the heading error and fourth difference. Magnetic interference was mitigated by extending the magnetometer‐unmanned aircraft system separation distance to 1.7 m, shielding, and demagnetization. The stationary calibration yielded an improvement ratio of 8.595 and a standard deviation of the compensated total magnetic intensity of 0.075 nT (estimated Figure‐of‐Merit of 3.8 nT). The box calibration also yielded an improvement ratio of 3.989 and a standard deviation of the compensated total magnetic intensity of 0.083 nT (estimated Figure‐of‐Merit of 4.2 nT). The stationary and box calibration solutions were robust with low cross‐correlation indexes (1.090 and 1.048, respectively) when applied to a non‐native data set.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.