Developing multi-sensor drones for geological mapping and mineral exploration: Setup and first results from the MULSEDRO project

The use of Unmanned Aerial Systems (UAS), also known as drones, is becoming increasingly important for geological applications. Thanks to lower operational costs and ease of use, UAS offer an alternative approach to aircraft-based and ground-based geoscientific measurements (Colomina & Molina 2014). Magnetic and hyperspectral UAS surveys hold particular promise for mineral exploration, and several groups have recently published studies of magnetic data collected by UAS for such applications (Malehmir et al. 2017; Cunningham et al. 2018), although equivalent studies using hyperspectral data are still rare (Kirsch et al. 2018). Combining both techniques is particularly useful. Magnetic measurements play an important role in mineral exploration, since magnetisation in rocks is mainly associated with magnetite and other iron minerals, which can be used in mapping and targeting of mineral deposits (Dentith & Mudge 2014). Hyperspectral imaging (HSI) is a powerful exploration and mapping technique in areas where the rock surface is well-exposed, and where geological units and mineral compositions can be estimated from spectral features of the electromagnetic spectrum in the visual and infrared range. This paper reports on the setup of UAS multi-sensor systems that can collect both magnetic and hyperspectral data, developed within the EU-funded MULSEDRO project (MULti-SEnsor DROnes). We focus on small, lightweight solutions with take-off weights less than 5 kg. This is because regulations restrict commercial UAS operations in many countries according to take-off weight, flight height and operating range – typically, only operations in the (extended) visual line of sight are allowed. Lightweight systems are also particularly advantageous to support geological field campaigns as they can be quickly deployed to survey areas of interest. Here, we use both a multi-copter and a fixed-wing UAS as both platforms have advantages. Multi-copters can fly at low elevation and speed, allowing them to follow strongly varying topography and collect high-resolution data that are comparable to traditional ground surveys. Fixed-wing UAS reach higher speeds and have longer endurance, such that larger areas can be mapped in a short time – comparable to smaller helicopter surveys. In addition, we have developed a new integrated positioning system (IPS) for UAS use that is not based on GPS. This affords accurate positioning within areas of poor GPS reception, such as mining tunnels and narrow valleys.