When confronted with a change in regulatory policy affecting how stockpiles could be verified, coal mining operations in central Alabama demanded immediate compliance from the engineering firms that oversee that activity for them. The firms were at a crossroads: Find a way to meet the new demands, or risk losing those clients.

For PERC Engineering, which counts several mine and quarry operators among its key clients, walking away wasn’t an option. Founded in 1981, the Jasper, Ala.-based firm (whose acronym originally stood for Permitting, Engineering, Reclamation and Consulting) employs between 40 and 50 personnel and offers a broad range of services covering everything from civil engineering and testing to surveying and mine engineering. According to 26-year veteran Lynell Early, the company’s vice president of surveying, doing work for area mines has been a big part of the company’s focus for a long time. “The Warrior Coal Field runs through this area and, as a result, has spawned a number of coal companies which have managed to remain operational, even in these tough times,” he says. “We provide a number of services for the mines--as well as for area limestone and aggregate quarries--one of which is verifying onsite inventories. That can include piles of material that have already been mined or quarried, or material that remains in place awaiting such action.”

Early says there are alternative methods to verification. “The operator of the mine or quarry could weigh each truck as it leaves, but that’s inefficient and it would be far too costly to slow them down for weighing,” he explains. “Aerial photography can be a bit on the costly side as well but, more importantly, it puts the operator totally at the mercy of the weather. If the site is clouded in, there’s simply no chance of an aerial photo taking place. So, many of the operators turned to engineering firms like us to survey the piles or benches and give them their numbers. And that’s what we did for a lot of years.”

Scans can be colored to indicate anything from the intensity of the signal, to the elevation (as shown here).

Changing Their Mines

The change in practice at the mine operations was the result of a mandate from the Mine Safety and Health Administration (MSHA), which said that mine operators had to ensure the safety of any personnel walking on piles of material that had reclaim tunnels beneath them. According to Early, traditional surveying of a client’s material piles--many of which did, in fact, have tunnels beneath them--couldn’t be done without walking the piles. “We looked at a number of alternative ways to stay with the traditional surveying approach while, at the same time, complying with the MSHA mandate,” he says. “But they were either too cumbersome or too slow.”

The firm had been regularly attending seminars hosted by its equipment supplier, Earl Dudley Inc. in Birmingham, Ala. Several of these seminars focused on the use of Topcon’s GLS-1000 Laser Scanner, a tool that caught Early’s attention for its speed and data capture abilities. The unit sends out a laser beam that captures data at 3,000 points per second at a range of 500 feet to a typical surface and can offer an extended range to 1,100 feet for more reflective surfaces. The result is a dense point cloud that can be post-processed to yield 3D models of the object or surface being scanned. “It was exactly what we needed,” Early says. “We couldn’t wait to get familiar with it and put it to work in the field.” 

Wes Bertoldi, PERC Engineering surveyor, defines his scan area in the GLS-1000 before making an initial scan.

Fine-Tuning the Process

If any single phrase can sum up PERC Engineering’s first real effort with the GLS-1000, it would be “too much of a good thing.” Early says Earl Dudley’s people were outstanding in getting them up and running, and PERC personnel themselves experimented with the unit a fair amount in and near their office before heading out to a jobsite. Nothing, however, prepared them for what the equipment would do in a real work situation. “The first time we went to an operator’s site, we shot a stone pile which was about 1,000 feet in length,” Early explains. “Using standard surveying techniques, we would normally generate anywhere from 1,500 to 2,000 points. Using the GLS-1000 and 10 separate scans, we got more than five million.”

The numbers were impressive--until the firm realized it had to find a way to manage all of those points to create the models. “We quickly found that there’s no reason for millions of points when far fewer will do just fine,” Early says. “Now, we generally do no more than seven scans, which gives us about 400,000 points and a nice, manageable point cloud.”

Although more in-office time is spent manipulating the data after the scan compared to a traditional surveying approach, Early says there’s no denying the fact that the laser scanner produces both a better product and real, measurable savings. “On an application like this [volume verification], the accuracy is far better with the scanner than what we could do otherwise,” he says. “We are actually getting the shape of the pile; if it gradually curves, we get that. There is no doubt in my mind that we are getting a more representative reading of what’s there than if we were out there with a stick.”

Since the GLS-1000 uses an invisible, Class-1, eye-safe laser, the equipment can be used even when personnel traffic is present, so no disruptions to mine or quarry operations occur during scanning.

As to savings, Early says that in mining applications alone, PERC can now do the same amount of work with three solo operators that it used to do with three two- or three-person crews. The firm is also gradually reducing the amount of office time required to process the point clouds in Topcon’s ScanMaster software and create models. “What’s important is that we are confident the savings in field time will allow us to get and do more work without adding more people,” Early says. “That’s a benefit we hadn’t foreseen.”

A point cloud rendering from the laser scanner can be modeled and subsequently used to determine volumes and quantities of material stockpiles.

A Vision for Scanning

Early believes PERC has only scratched the surface with regard to how it can benefit from the scanning technology. “We see a lot of different uses for the scanner in our future in addition to the work we already have,” Early says. “For example, we used it on a project in which a client suspected that a high-tension tower was subsiding because of mining activities beneath it. So we scanned the tower before the mining activity and then again a month later and presented the findings to our client. It was determined that one of the anchors had moved, resulting in a minimal twist of the tower of about 6 or 7 inches. Just to be able to give them a representative 3D model of the results was really a feather in our cap.”

Early also envisions PERC using the technology in highway construction projects, utility installation projects, improvements in commercial properties and as part of a municipal GIS effort. “Initially we were intimidated by the thought of managing the data--that was one of the biggest reasons we hadn’t jumped on board with laser scanning sooner,” he says. “Now that we have a decent handle on working with point clouds, we will look at every scanning job we can get.”

For PERC and other firms, laser scanning is simply the next evolution in surveying technology. “It’s a lot like when GPS first hit the market,” Early says. “Everyone, including us, was a bit skeptical, a little gun-shy. In fact, before we purchased our first Topcon receiver and signed onto Earl Dudley’s iNET network, we used to hire a Florida firm to do our GPS. But as time went on we embraced the technology and now it’s just the way business is done.

“We see the same thing happening with scanning.”