Real-time compensation of magnetic data acquired by a single-rotor unmanned aircraft system
L. Tuck, C. Samson, C. Polowick and J. Laliberte
Journal name: Geophysical Prospecting
Issue: Vol 67, No 6, July 2019 pp. 1637 - 1651
Info: Article, PDF ( 5.15Mb )
Two methods for low-altitude calibration of a single-rotor unmanned aircraft sys-tem 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 lim-its 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 sys-tem 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 dis-tance 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 mag-netic 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 compen-sated 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.