Unmanned aerial vehicles (UAVs) are one of the newest technological tools being adopted by the mining industry to survey mine properties. Gone are the days of the lone surveyor, armed with a GPS device, driving across rugged mine property for hours to mark mining activities. Now a UAV with the right camera and data-processing software can take pictures and provide better data, faster.
“This is great for surveyors because it means they can spend less time collecting data and more time using it,” says Iain Allen, Barrick’s Senior Manager of Geographic Information Systems. “This technology also allows us to survey areas that were previously too dangerous to send anyone.”
At the Barrick-operated Pueblo Viejo gold mine in the Dominican Republic, a small fixed-wing UAV, the SenseFly eBee, can survey a mine area of 450 hectares, the size of 750 football fields, in four hours. The UAV collects survey data from pre-marked ground control points using GPS technology. The resulting “orthophotos” provide rich detail of all exposed surfaces in pits, quarries and stockpiles. They also help track the stability, construction and volume of materials within tailings storage facilities. They even account for the curvature of the Earth’s surface and correct distortion for digital maps to reflect distances more accurately. These activities strengthen already robust on-site monitoring activities and provide greater detail than traditional tracking methods.
UAVs are an efficient way to help us track the stock piles, optimize space at site and ensure we’re sending the right ore to the mill
With further processing, the orthophotos will provide a 3D model of the area surveyed, allowing the surveyors to better calculate ore and other material volumes and track changes in three dimensions.
Case in point: Pueblo Viejo processes up to nine different types of ore, but lacks the space to stockpile them separately. Hence, different ores are stacked on top of each other. While that may seem like grounds for a mix-up, the three-dimensional models produced by the UAVs can distinguish between the stockpiles, ensuring that the right mix of ore is sent to the mill at the right time.
“The UAVs are an efficient way, both economically and practically, to help us track the stock piles, optimize space at site and ensure we’re sending the right ore to the mill,” says Sean Jefferys, Pueblo Viejo’s Chief Surveyor.
The eBee UAV has a Styrofoam body, making it very light. It also has a 50-minute flying time under ideal conditions, and has numerous programmed safety features. It will, for instance, return to its launch site if it passes a pre-set low-battery level, ensuring it doesn’t run out of juice and crash. Battery error, poor GPS coverage and strong winds are other scenarios that will automatically return the UAV to its launch point where it will make a controlled descent.
Pueblo Viejo has a government permit to fly the UAVs within the mine site at no higher than 500 feet.
Before the introduction of UAVs at Pueblo Viejo, a Light Detection and Ranging (LiDAR) scanner was used to collect survey data. A LiDAR scanner might take as long as five hours to gather data of a complete pit or stockpile. A LiDAR scanner costs $180,000 and the scanning process introduces a greater possibility for human error. One eBee costs just $20,000, meaning it’s possible to purchase nine eBees for the cost of one LiDAR scanner.
The average flight of Pueblo Viejo’s UAVs takes 15-20 minutes, plus two hours to process the data and generate orthophotos. When you factor in the lower costs of maintaining and operating the site’s six UAVs, the time saved gathering and processing data, and the greater accuracy of the data, it’s readily apparent which technology is preferred.
“The total cost for procurements, repairs and upgrades of our six UAVs has been $120,000 over two years,” Jefferys says. “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.”
The operational advantages of UAVs accumulate quickly. Jefferys and his team survey pits and stockpiles every two weeks, which was not previously possible due to the manpower required to traverse Pueblo Viejo’s hilly, brush-covered terrain. The UAVs also improve the quality of the data gathered while freeing up personnel to analyze this data.
“The UAVs allow engineers to work with near real-time data,” Jefferys says. “The proof is in the pudding because of how much the end-users rely on it. The UAV data has enabled clearer communication of daily mining plans at all levels. It is an established production tool.”
The LiDAR scanner still has its place in surveying, although now it is used more sparingly. The advantage that the LiDAR scanner offers is it can penetrate thick brush cover to generate data, whereas UAVs cannot. The UAV is used only for areas with no ground cover. When surveys of larger areas of the mine are required, something the UAV cannot provide, the survey team uses satellite imagery.
The latest eBee models have Real Time Kinematic (RTK) Differential GPS functionality, meaning each photo is automatically assigned GPS coordinates the moment the photo is taken. This will obviate the need for ground control points, saving considerably on time while capturing the elevation in the hilly terrain around Pueblo Viejo to within three centimeters. Because it is relatively new technology, the current obstacle to acquiring RTK navigation is cost. Nevertheless, Jefferys says the existing UAV technology has greatly enhanced efficiencies and the quality of survey data at Pueblo Viejo.
“It’s technology that’s really under-utilized in the mining industry,” he says.