GeoWorld

GeoWorld August 2012

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Infrastructure DON TALEND DON TALEND started getting drawings on the eight radiuses, and I saw the complexity of it, I insisted on getting the scanner," he adds. Fugera estimated that, using traditional methods, it would take at least two weeks to shoot the approxi- mately 2 million points required to as-built survey Schuff's steelwork on the long east side of the guitar wall, which has an estimated 4,000-5,000 connec- tions to the main steel structure. He also estimated that it would likely take three or four more weeks to determine where Schuff's steelwork was located rela- tive to the main steel structure. Chris Clay, Schuff's licensed surveyor on the project, Point-cloud file data are easily entered via the GLS-1500 keypad. had operated a total station, but, like Fugera, this was his first project using scanners. And he agreed that laser scanning was the only realistic way to develop an as-built survey of the steelwork. "This is the largest structural job I've worked on," "It wasn't until we got into the curvature section that we figured the scanner would give us a lot more accu- racy," says Fugera of the Topcon Positioning Systems GLS-1000 and GLS-1500 laser scanners rented out by Earl Dudley Inc. Given the design of the radius walls, determining the X, Y and Z dimensional locations of every quarter-inch of the steel beams using conven- tional surveying equipment would have been too costly. This process would've been especially cumber- some on the center's east side. Fugera noted that the guitar wall on this side featured eight radius variations and five pitch variations at the roof. Fugera, however, didn't plan on using a scanner when Schuff began its work on the project. "Once I notes Clay. "I've surveyed some commercial work— strip malls, stuff like that—but not to this scale. This is a lot more intricate. That's where the scanner comes in. Trying to collect that information with just the total station and a data collector—no chance." Sophisticated BIM High-speed precision laser scanning is allowing con- tractors such as Schuff to save a lot of time in develop- ing as-built surveys and correcting construction errors, preventing other trades from compounding errors within their work. As a result, the technology saves the entire building team—and, ultimately, the building owner—time and money. It serves as a key element in building information modeling (BIM), a discipline that continues to expand its technological sophistication. Topcon's GLS-1500 collects points at a rate of 30,000 points per second—10 times that of its previ- ous GLS-1000—and a range of 150 meters. Having experienced an exponential increase in as-built sur- veying productivity with a GLS-1000 vs. a total sta- tion, Schuff began to double its productivity with the newer instrument. In late fall 2011, Schuff was erecting steel near the facility's southeast corner and continuing to work its way around in a clockwise direction. Clay set up a GLS-1500 outside the guitar wall at ground level. He identified multiple magnetic targets that had been placed on several steel beams forming a large horizon- tal rectangle on the eighth level. The target locations were surveyed with a total sta- John Fugera views GLS-1500 data in 2-D CAD and 3-D Tekla Structures files, showing Schuff's steelwork against the entire building frame. 28 GEO W ORLD / A U G U ST 2O12 tion and tied to the grid formed by control points based on the official building survey and a 3-D BIM model of the entire building. He measured the center of the tar- gets from building control points using a total station and scanned the targets. By doing this, Clay tied the target locations to the building model and the official survey grid.

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