Shigen-Chishitsu
Online ISSN : 2185-4033
Print ISSN : 0918-2454
ISSN-L : 0918-2454
Articles for Annual Meeting for Prospecting of Ore Deposits
Drone-based Airborne Geophysical Survey – With a Focus on Magnetic Survey –
Ryunosuke YANONobuhiko SHIGA Yoshiharu TAKIGAWAKazuhiko YAMANAKA
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JOURNAL FREE ACCESS

2024 Volume 74 Issue 1 Pages 9-13

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Abstract

Currently, the use of drones is progressing in various areas of society. In Japan, since the late 2010s, the necessary technological development for social implementation of environmental improvement and operation management systems has been underway aiming non-line-of-sight flight in manned areas. MINDECO has been using drones since around 2016, starting with topographic surveying at tailings dam and open-pit mining sites, and has been engaged in aeromagnetic surveys, ground temperature monitoring, and the movement of equipment and supplies, accumulating a track record of achievements. In drone geophysical survey, lightweight, non-contact sensors such as optical sensors (visible-light, thermal infrared, and hyperspectral cameras), LiDAR, and magnetic sensors are used for the sensors mounted on the drones. Multicopter drones can also hover and operate automatically/autonomously. It can reproduce planned flight paths precisely. Fixed-wing drones can glide and have a range of 90 minutes, and surveys using relatively lightweight optical sensors can survey a wider area. Aeromagnetic drone surveys use a multicopter drone, an onboard optical pumping magnetometer, and a magnetometer at a fixed point for daily change compensation. If conditions are favorable, the drone will fly 25 to 40 km per day, repeating 20-minute flights 6 to 10 times. The ground altitude is about 40 to 80 meters and the line spacing is about 100 meters. Except for drone takeoffs and landings, measurements are made according to a flight plan prepared in advance, with automatic flight along the terrain surface. Due to range limitations, flight plans are created to cover the entire survey area from multiple takeoff/landing points. More than 900 km have been measured by drone aeromagnetic surveys over the seven years since 2017. The objectives are mineral exploration and civil engineering exploration. The results of the magnetic survey for the mineral exploration showed that a low magnetic anomaly zone, which is thought to be caused by the dissolution of magnetic minerals due to hydrothermal alteration, was detected. The civil engineering survey was used to identify the serpentinite distribution area in the mountainous area, which is difficult to access by geological survey. It is known that the higher the amount of magnetite produced in the process of serpentinization of peridotite, the higher the magnetic susceptibility of serpentinite, and the drone survey helped to detect such serpentinite distribution areas. Aeromagnetic survey by drone demonstrates its measurement efficiency and resolution in surveys of several km2. In the future, the scope of application will be further expanded compared to the past due to the evolution of batteries and motors and the downsizing and weight reduction of onboard equipment. On the other hand, when drones are used overseas, there may be problems due to differences in legal systems for use of drone, and/or the issue related to the import/export of equipment, so it is necessary to carefully gather information on the local legal system before using drones overseas, or to hedge risks by using local contractors for the procurement and operation of drones.

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© 2024 The Society of Resource Geology
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