For 140 years, nickel mining has played a critical role in the economy of New Caledonia, an archipelago nation in the South Pacific Ocean. With nearly one-quarter of the world’s known nickel resources, New Caledonia relies on the mining of nickel ore and ferronickel to account for 95% of its exports. In modern times, surveying has become an important — although expensive, time-consuming and sometimes dangerous — part of mining activities on the island. Th roughout the year, operators periodically need timely and accurate surveys to optimise their extraction tasks.
As the mining operations advance lower on the mountains and closer to delicate farm lands and coastal harbours, the New Caledonia government agency that regulates mining (DIMENC) asks for regular delivery of updated maps to closely monitor the impact on Grande Terre’s other natural resources.
In 2012, AB Concept, a technical consulting firm, teamed up with SYPOS, a surveying solutions distributor in the region, to introduce Unmanned Aircraft Systems (UAS) to the local mining industry as a safer, faster and less expensive alternative to traditional surveying and mapping. The Gatewing X100 UAS used in the first project met or exceeded all expectations.
The appeal of UAS
AB Concept delivers a full line of mapping capabilities to the entire life cycle of a mining operation from initial exploration and excavation to environmental remediation. For topographic survey projects, its crews use traditional GPS/GNSS equipment. Time-consuming by nature, these field surveys take even longer in an active pit mine due to safety considerations when crews work on the notably steep slopes.
Some survey and mapping companies have access to aircraft from which both imagery and LiDAR data are collected, ultimately generating planimetrics, orthophotography, digital elevation models and volumetric calculations. Mine operators typically request for 1:1,000 or 1:2,000 scale orthophotos for planning purposes.
Due to the rapidly changing topographic conditions in the mines, surveying and mapping companies face the constant challenge of collecting their raw data, processing it and delivering end products to mine operators and government regulators before the information is out of date.
SYPOS’s Gatewing X100 UAS includes the aircraft (called the ‘Wing’), launcher, remote controller, image processing software, and camera. Operating at a lower altitude than an airplane, the digital camera offers horizontal and vertical photogrammetric accuracies of 5 cm and 10 cm, respectively. And the software is capable of generating multiple mapping products, including orthophotos, digital surface models, digital terrain models and planimetric maps.
Compared to ground surveys, AB Concept saw crew safety as an immediate benefit since the UAS would fly over the notoriously steep cliffs in the pit mines. Speed was the other anticipated advantage. In good weather, flights could be completed in a day with the image data downloaded for processing immediately after landing.
Mapping with Gatewing
SYPOS and AB Concept worked closely on the first commercial mapping project in New Caledonia at an open pit operation where a valuable nickel ore called garnierite is mined. AB Concept was contracted to map a garnierite mine operation covering 200 hectares, putting it in the category of a medium-sized excavation site.
Prior to the flight, personnel from the two companies visited the mine to select take-off and landing points and note vertical flight obstacles. They also sketched out a flight pattern for the UAS to follow in covering the complete site. Field crews then marked and surveyed 11 ground control points throughout the operation. Flight planning software was used to create the pattern flown by the UAS. Since the total mine area would be covered in several flights, the software calculated the best pattern of flight lines for each one. Less than a week after receiving the purchase order for the project, the team was onsite at the garnierite mine for the first commercial collection.
After being launched from a sling-shot-like device on the ground, the Wing automatically manoeuvres to its correct altitude, 150 meters in this case, and to the start point for its flight plan. From there, the Wing became autonomous, flying the programmed pattern and collecting highresolution imagery as planned. The Gatewing craft covered about 100 hectares per flight and completed up to four flights in a day. A total of three flights were needed to map the entire mine site.
The Wing returned to its designated landing point after each flight. Data was downloaded from the onboard camera to the image processing software called Stretchout. Shortly after the flights, AB Concept delivered a high-resolution orthophoto of the entire site at +/- 5 cm resolution, DSM, DTM and planimetric vector map. The vectors pinpointed locations of roads, water features, and the tops and bottoms of main slopes in the mine.
The cost of the DEMs was one quarter compared to what it would have been for a survey crew and airplane. More importantly, the GNSSequipped team would have surveyed only 5 hectares per day compared to 400 hectares for the UAS. The spatial resolution and accuracy of the orthophotos exceeded that of imagery captured with a regular airplane. The garnierite mine operator has already asked AB Concept to bring the Gatewing X100 UAS back for the next surveying and mapping project at the site. In addition, the companies are now gearing up to bid for other open pit mine mapping projects in the region.