300 feet from the instrument. In 10 scanning set ups, the crew captured the entire 40 acres in a single seven-hour shift. “I didn’t think I’d use the scanning functionality on a huge, flat surface so I wasn’t sure how it would perform, particularly in low light,” says Hudson. “I went to the site expecting it would be a three-night job, and I was shocked that we got it all in one night. Our dealer, Duncan Parnell, had assured me that darkness wouldn’t be a problem, and they were right. I not only acquired millions of 3D points that clearly show all the concrete seams and subtle grade variations, I captured substan- tially more data in nearly 13 percent of the time.” An additional efficiency benefit came from the “big picture” screen of the TSC7 and the integrated survey workflow provided through Trimble Access, which enabled crews to seamlessly manage the data from myriad project tasks and sync data between field and office in real time. “The large controller screen makes it really easy to see in any environ- ment like bright sun, overcast, in the middle of the night and even wear- ing polarized sunglasses,” says Hudson. “That allows us to quickly set up new jobs and move between jobs. And with Trimble Access we can transfer data between the office and field in real time and check emails so it’s like having your office with you.” Back in the office, Hudson processed the point cloud using TBC software and its automated extraction tools to remove any extraneous features such as parked airplanes. After cleaning the data, he created a 3D topographic model of the 40-acre concrete apron and exported it into AutoCAD to produce a final 3D surface. Two days after capturing the data, CES delivered the topographic survey to their client. Since finishing that survey, CES teams have been back on the SCT site with their S7 total stations to collect the locations of all the sewer and storm systems across the 300 acres. Work on the SCT project will continue through 2022. With the company involved in 16 active projects at the airport, Hudson cannot readily predict when the SX10 scanning functionality will be used again––they use it every day as a total station––but he says it’s only a matter of time. “Since purchasing the SX10, I’m using it in on projects I never thought I would, like scanning features at busy road intersections and large- diameter water main projects,” says Hudson. “Its versatility, the ability to scan and survey in one instrument, its ease of use and its speed save us so much time in the field. And on such massive projects like CLT, we need that. It does not sit idle.” Between Destination CLT and other on-going projects, CES won’t be sitting idle, either––it just opened its third office in Columbia, S.C. With a docket that looks as full as CLT’s departure board, those phan- tom frequent-contractor points probably wouldn’t get used anyway.
However, because this site is located within CLT’s airfield, CES was required to perform their work overnight to avoid disrupting airport operations and to ensure their safety and the safety of airport staff and airline personnel. They set control using a number of Trimble R8s GNSS receivers, occupying each control point multiple times and then calculating the averaged coordinates for each point. They then ran a closed traverse loop using the S7 for horizontal control and the DiNi level for verti- cal control to within 0.01 ft. With control established, three different survey crews used multiple S7 total stations and TSC7 data collectors to collect all the field data including ground shots, utilities and critical tie-in points. There was one particular area, however, that gave Hudson pause: a 40- acre, concrete cargo area. This “flat” apron is comprised of 107, 20 ft x 20 ft concrete slabs laid in a grid pat-tern. CES was required to locate and pinpoint every concrete joint, or seam, within this vast area, along with any grade change over the cargo space and taxiways. “To acquire that kind of survey over 40 acres would have required us to take 5,000-7,000 shots using our total stations,” says Hudson. “We’d have to set a rod every 20 feet, take a shot, and move to the next point 20 feet away. Although our technology would deliver on the precision, I calculated that it would take eight nights of work to complete it. Hav- ing seen the speed, range and accuracy of the SX10, I thought it might be a better alternative.” He thought right. Arriving on site at 11PM, he and his colleague used the previously established primary control network and set additional “spur” control points as needed. Setting the scanning total station on a chosen control point, Hudson captured the scene, collecting not only the concrete joints and surface elevation variations, but also the tops and bottoms of retaining walls, storm grates and building corners at distances up to Actual scanning image of a portion of the 40-acre concrete cargo area, with dots representing millions of points collected by the SX10.
MARY JO WAGNER is a Freelance Writer, Editor, and Media Consultant based in Vancouver, BC. She can be reached at mj_wagner@shaw.ca.
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july 2020
csengineermag.com
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