Taking flight

With so many applications and potential benefits it’s no wonder that unmanned aerial vehicles (UAVs), more commonly known as drones, are becoming an increasingly common sight at mine sites.

Compared with larger manned aircraft, drones can offer much greater manoeuvrability and accuracy. They can fly at lower altitudes and capture complex surfaces such as crevices and protruding elements. Because of their smaller size, they can also better navigate through narrow passages and corridors.

Fuelled further by their low cost, the number of drones in mining is expected to grow rapidly in coming years. More and more companies are developing UAVs specially designed for mining applications, such as image mapping, monitoring and communications.

Take UAV manufacturer Aibotix, for example, which the Swedish Hexagon Group acquired in February 2014. The company’s Aibot X6 is equipped with a variety of intelligent sensors such as a GPS receiver, gyroscope, accelerometer, barometer, magnetometers and ultrasonic sensors that enable it to fly on its own. It takes off, lands and shoots photos automatically, and it can execute flights that have been mapped out on a computer beforehand. It is equipped with safety features such as a GPS cage for training purposes and a return-home function in case of signal failure or low battery.

While on these autonomous flights, the Aibot X6 can capture high-resolution, geo-referenced images of open-pit mines using digital cameras, hyperspectral sensors or thermal imagers. These images are further processed into orthophotos, 3-D models and point clouds with a ground sample distance as small as 10 millimetres. It is used to monitor and survey open-pit mines, especially in Australia and South America.

“We see a very high potential for the mining industry to employ drone technology in these regions, and also in Africa,” says Jörg Lamprecht, CEO of Aibotix.

Mapping and monitoring

Today, drones can be used to generate 2-D or 3-D maps to survey existing mines or for exploration. They can also be used to create ‘orthomosaics’ through a process called orthorectification, in which raw aerial images are transformed into orthoimages – images with the same geometric properties as maps, where optical deformations such as those due to perspective are corrected. Multiple orthoimages can be stitched together to form an orthomosaic – a paramount product to update maps and provide a detailed view of the landscape, which is an invaluable tool for exploration purposes.

Monitoring is another important use for UAVs in mining, primarily to survey stockpile and waste dump volume. This includes assessing inventory, calculating the volume of stockpiles and determining removed volumes. Drones can also monitor pipelines and slope stability, and they can track environmental management while also being used for boundary surveillance. Drones are efficient at inspecting tailings ponds and equipment, particularly those that are in dangerous locations or simply difficult to access.

In 2014, one of the largest diamond mines in Western Australia successfully completed a survey of its mine using an Aibot X6 UAV. Over eight flights, each lasting 10 to 15 minutes, the Aibot X6 covered almost 100 hectares of the mine. All the images and data collected by the UAV were then used to create an orthophoto, a point cloud and a 3-D model, with a ground sample distance of 2 to 6 centimetres.

“Using the Aibot X6, we are able to generate data of the open pit mine with an accuracy that would not have been reached with a common airplane,” says Sam van Eldik, of CADS Survey, who undertook the survey.

Extremely cost-efficient

One of the biggest advantages offered by drones is the potential to reduce costs. Compared with a helicopter or winged aircraft, the average drone is substantially less expensive to operate and generally requires only one person, as opposed to an entire crew.

The Pueblo Viejo gold mine in the Dominican Republic formerly used a light detection and ranging (LiDAR) scanner to collect survey data, but it decided to switch to SenseFly’s eBee UAVs since one unit costs one-ninth as much as a LiDAR.

“The total cost for procurements, repairs and upgrades of our six UAVs has been 120,000 US dollars over two years,” says Sean Jefferys, Pueblo Viejo’s chief surveyor. “We get about 300 flights out of a single UAV before something needs to be replaced. We can cover much larger areas with better-quality data than we ever could through traditional methods.”

Future of flight

Like all new technologies, regulations concerning the use of UAVs are still in their infancy, and in many countries using drones can be difficult because of legal restrictions. There are no recognized standards and protocols for how UAVs should share airspace with manned aircraft. In the United States, drones can only be used by public agencies, while in many other countries they must remain within eyesight of operators. As the technology becomes more widespread and accepted, however, governments will be forced to update legislation accordingly.

At this stage, UAVs are a complementary technology and cannot replace manned surveillance entirely. They offer limited endurance and can only carry a small payload, which restricts the area they can cover. Still, UAVs have already made substantial progress in the mining industry, and as the technology continues to rapidly develop and improve, their use will become increasingly common.