Drone magnetic surveys for active volcanoes: a case study of Izu-Oshima volcano, Japan

Aeromagnetic surveys using unmanned aerial vehicles (UAVs), or drones, are becoming popular as a useful subsurface survey method, especially in active volcanic regions. In this study, the results were compared for magnetic surveys using an unmanned autonomous helicopter (UAH) and a multicopter over Izu-Oshima volcano, Japan. As nearly 40 years have passed since the latest 1986 eruption of the volcano, the next major eruption is anxiously anticipated in the near future. High-resolution aeromagnetic surveys are expected to elucidate the detailed subsurface structures associated with the past and on-going volcanic activity to mitigate volcanic hazards of the volcano. Consequently, the drone magnetic surveys were successful in mapping dikes, a hydrothermally altered area, and other areas that had not been mapped by the classical manned airplane survey. Among drone magnetic surveys, multicopter surveys are superior to UAH surveys in terms of the spatial resolution of measurements and analytical structure of shallow underground areas, but inferior in terms of the survey coverage. The multicopter can only cover small areas in light wind conditions. Only the manned aircraft are able to survey inhabited areas. The survey aircraft should be chosen on the basis of the survey area to be covered, the resolution required and whether or not the area is inhabited.