Satellite-based Global Positioning Systems (GPS) allow for precise and real-time navigation of mining vehicles. This translates into increased productivity, efficiency and safety for the surface mining industry. However, no directly comparable technology exists for accurate tracking in underground mining operations because satellite communications are unavailable in the space.
Dr. Joshua Marshall, an assistant professor in The Robert M. Buchan Department of Mining at Queen’s University, and his research team have been working on a map-based underground GPS (uGPS) technology that could be used in underground mines.
The team sporadically placed radio frequency identification (RFID) tags about every 100 metres throughout the CANMET Experimental Mine in Val-d’Or, Québec. Afterwards, they sent an underground vehicle equipped with sensors and a RFID reader into the mine to collect information about the environment – tunnels, corners, intersections, etc. The stationary RFID tags serve as landmarks (their locations are initially unknown) that are automatically surveyed by the RFID reader as the vehicle passes by.
“We then ‘stitch’ together the data to create a consistent representation of the environment,” says Marshall. The map can then be used to navigate a mining vehicle through the tunnels of the mine.
Marshall says RFID tags are not required to determine the position of vehicles underground, but placing RFID tags throughout the tunnels splits the mine into smaller, more manageable areas. The different areas of the mine are divided into submaps, which combine to form a global map of the mine – like an atlas. “Without this technique, one needs a computer with a very large amount of memory to process the whole map all at once, which is not practical,” Marshall states.
The team has shown their technology can arbitrarily map large areas (e.g. tens of kilometres). “Of course, the larger the area, the more tags would be necessary and the longer it would take to make the maps after data collection,” says Marshall. But the maps can be made using a normal computer, and the size of the map that can be generated is only limited by the computer’s available memory.
Compared to using RFID tags alone for vehicle navigation, the uGPS technology provides higher accuracy positioning and reduces the time needed to locate the vehicle. “We can see, within a metre or so, where the vehicle is in real time,” Marshall says. “If you were simply to use RFID tags you could not do this. You would be able to guess where the vehicle is whenever it passes near a tag, which could be 100 meters away!”
There are some uncertainties in the maps since the vehicle’s sensor scans less than the full 360 degree view of the vehicle’s surroundings. But the team’s maps are still much more detailed than typical survey maps and provide environmental features that would not be seen normally (e.g. bumps in the walls).
The team is currently working with industry partners to develop and deploy their uGPS technology in an underground mine in the United States. Marshall envisions the robotic mapping and underground positioning technologies to be a useful asset management system for underground operations in the future.