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Surveying large industrial parks has always been challenging work. Projects often encompass a variety of sizes and types of buildings and other structures, and it’s not uncommon for crews to have to return to the site multiple times because some feature or measurement from the initial survey was missed or needs to be expanded on. Revisiting the site to resolve these issues can be costly, not only in budget dollars but also in lost project time. It was a process that Barghausen Consulting Engineers, based in Kent, Wash., believed could be streamlined with the use of advanced technology.
When Barghausen was contracted in March 2011 to conduct a full ALTA survey of a 90-acre industrial site as part of a new construction-related boundary-line adjustment, the firm decided laser scanning would provide the best solution. “The site contains about 50 structures of different use, including manufacturing, office and storage, and it includes everything from 100-foot-plus tall buildings to underground tunnels,” says Trevor Lanktree, PLS, one of the company’s project surveyors. “We had known about laser scanning for some time, and this seemed the ideal project to give it a try.”
Lanktree had already been in touch with his local equipment dealer, Collin McCoy from the PPI Group, who had been training him on the use of a Topcon GLS-1500 laser scanner. Barghausen decided to rent the system for the industrial site survey project. Over the course of six weeks, Lanktree and his crew set up in 88 scan positions and collected a total of 110 scans on the industrial park site. Lanktree said the project could have been completed much faster, but the crew had to work around traffic and weather constraints. While a traditional survey probably would have netted about 20,000 points, Lanktree estimates the scanner gave them close to a billion. “The laser scanner gathers data at a rate of about 30,000 points per second,” he says. “It is really an impressive piece of equipment.”
The project also gave the crew a chance to test the accuracy of the scanner. “Collin initially told us that it has a single point accuracy of about .16 inch up to 500 feet, and we were skeptical,” Lanktree says. “But we did some long-range scans in which we set up at the south end of this project and shot all the way through it. In those scans, there is a tall building located more than halfway into the site that was generating what we thought were just random points. But when we got to a time when we could map the building, we found that those ‘random’ points from the distant scan were, in fact, right on the money.”
When actual scanning of the industrial site was done, the data was downloaded to an SD card and brought back to Barghausen’s offices for registration, a process in which each of the different scan position’s points is aligned with those from other scan position points. “When this procedure is done, you are left with a scan of the entire site,” Lanktree says. “At that point, if you could turn all the data on at once, you could virtually walk through the industrial park. So now, if the design team wants to know a specific detail on any feature--say the height of a wall, the location of piping, anything--we have it for them. It is that flexibility of data that is so key to the value of the scanner.”
Examples of this kind of “data mining” have already occurred on other projects Lanktree has been involved with, most recently on a job in which the contractor said he wanted to know the grade of a handicap access ramp for ADA compliance. “We went out and used the GLS-1500 to scan the ramp, the structure to which it was attached and a pretty decent piece of the area surrounding it,” Lanktree says. “Two days later, that contractor called saying he needed to show where concrete on the project ended, so he needed to revise his plans to include a profile showing everything 20 feet each way. A few days later, he then called back again and asked for a profile that covered 100 feet in either direction.”
Had they done that project with a traditional instrument, says Lanktree, they would have needed to go back out at least twice to get new measurements. That would have meant incurring the cost of a crew, travel time, setup time and other expenses.
“In this case, we simply pulled the file and kept growing the drawing to meet his needs,” he says. “That’s exactly the kind of scenario we are prepared for in the industrial park job. We have a wealth of information contained in the data from those 110 scans, and it will be a tremendous help for the design team on the project. It’s a perfect example of why scanning is so well-suited for this type of work.”