Aerial Look Under the Surface: Using UAVs for Advanced Geological Surveying
Pursuing new pastures and natural resources was the driver of migration, expansion and economic development for centuries. Today, this pursuit relies heavily on available technologies and their strategic use.
Getting to hard-to-reach places where a ground-based survey is hardly possible, and those tend to be the places with the most promise, is quite a challenge for an exploration geologist. That’s why aerial studies have been indispensable support for geological missions. The first electronic aeromagnetic survey by the USGS found petroleum reserves in Alaska in 1944. In the past decade, the emergence of purpose-designed unmanned aerial technologies made a truly revolutionary change in the geologic exploration industry.
Unmanned aerial vehicles (UAVs) are quick and effective performers. Each can fly dozens of bird’s-eye missions a day, and the routes of their short-time flights are easily adjustable: a field team member can quickly reprogram flight lines while replacing batteries between the missions. Drones hover at low altitudes between 40 and 100 m AGL and scan the ground in 400-meter-wide swaths. That enables UAVs to survey dozens of square miles in days and not weeks or months, which would be the norm for a ground-based exploration effort. And yet, they can be employed throughout the life-cycle of a mining project.
Also, UAVs provide huge savings compared to airplane or helicopter-based surveys, which are much more complex and costly to mount. Almost anyone nowadays can learn to operate a UAV, while learning to fly (safely) is a much more significant challenge.
To facilitate geologists’ work, UAVs can carry various instruments. The airborne tools cover huge territories at once and see landforms through dense vegetation and sediments. For example, the typical assortment of Microavia’s Fortis purpose-built geodrone includes:
· LiDARs that scan the ground surface map its features and details and create precise 3D models of the area
· Thermographic imagers designed to see the infrared radiation not visible to the naked eye
· Hyperspectral cameras to detect spectral radiance and examine the interaction of objects by capturing their wavelengths
· Ground penetrating radars (GPRs) to remotely discover hidden obstacles and possibilities without having to break the ground
· Magnetometers to find magnetic field anomalies
· Visible-light cameras to produce 2D orthophotographic images by using the RGB light band
· Gamma spectrometers to sense radiation
· Gas detectors to identify concentrations of methane that indicate the potential presence of oil fields
In exploration and surveying, UAVs are safer than manned aircraft. Drones like Fortis use preloaded 3D maps based on OpenGlobus and UTM coordinate systems to plan missions beyond the operator’s visual line of sight (BVLOS). That allows drones to be semi-independent in real-time during a mission. It means that UAVs do not need to rely on a pilot’s reaction time and ability to maneuver while they operate at low altitudes in areas with many obstacles.
In addition to loose-drape and tight-drape missions, which — with many limitations imposed by safety regulations — can be flown by fixed-wing aircraft or helicopters, UAVs such as Fortis have the terrain-following ability that enormously improves the collection of the dataset and the quality of bare-earth mapping. The 3D surface modeling produced by contour flying will be particularly useful for mineral extraction planning and management.
Most UAVs need no airfield and can take off from a tiny spot in the middle of nowhere an expedition is surveying. Of course, UAVs depend on batteries, but replacing and recharging power cells in the field conditions is times easier and cheaper than refueling the tanks of a plane or a helicopter — and then waiting hours for the aircraft to reach the survey area.
Moreover, UAVs are generally easy to maintain. Even someone without intensive technical training can do quick fixes if critical spare parts and essential tools are handy — so that geologists waste no precious time on the ground. Regardless, any experienced surveyor likely wants to complement a robust field-repair kit with a spare UAV, just in case. If one UAV crashes beyond repair, the cost of a failed mission would vastly outweigh the expense of having a backup UAV.
The UAV-acquired data is typically stored on an onboard solid-state memory card. Immediately after the landing, the dataset can be transferred to a field team’s laptop and analyzed — already in the field — with sophisticated software that compares and matches the detailed 2D orthophotos and 3D surface models to the thermographic and spectrographic images and provides valuable insight as to where and how to proceed. The study of drill cores and hand specimens picked from locations prompted by the drones will continue in laboratories.
Using UAVs for geological exploration provides quick results of consistently high quality. Still, it is pretty cost-efficient, particularly in comparison with the costs of months-long boot-on-the-ground expeditions and manned airborne surveys that involve many direct and indirect charges (aircraft lease, qualified crew hire, fuel, taxes, insurance, airfield and air control fees, non-productive aircraft approach/return times) and risks (starting from downtime due to adverse weather).
Many geoscanning service providers opt to adopt general-purpose drones produced by renowned UAV makers. Unfortunately, most such drones are, in fact, unfit for the harshness of geological exploration missions. Yet Fortis, developed by the Italian-founded, Dubai-based company Microavia, makes the difference. This heavy-duty, robust geodrone was explicitly designed to meet the requirements of tough geological survey jobs (Fortis is dust-water-proof, its operational temperatures range from -25ºC to +40ºC, it can fly against 15 m/s winds with gusts up to 20 m/s).
Mission-tested in Europe, Asia and Africa, Fortis can fly up to 40 km one-way missions and stay in the air for sixty minutes with a payload of 1 kg. With a dead weight of 12 kg, the UAV can lift the load of equipment and materials that equals its weight. However, the recommended payload is 3.5 kg, enough to be aloft for 55 minutes and scan terrain at the optimal speed of 27 m/s.
Fortis can carry proprietary and third-party instruments that are stabilized in-flight with a 3-axis gimbal to receive the best imaging product and satisfy the client. Microavia provides Fortis prosumer drones to clients on a DaaS license with flexible scopes and terms.
