January 3, 2013
3D scanning technology fast and accurate
With Building Information Modeling (BIM) gaining usage in the construction industry, the growth of 3D scanning and surveying seems logical.
“It brings the actual conditions of the jobsite into a 3D model so you can run an analysis of the information against the model,” explains Thomas Strong, the director of EllisDon’s virtual construction department, which includes a team of four field surveyors conversant in 3D scanning technology and six back of house staff.
The technology is proving “extremely effective” at producing accurate as-built drawings for a series of bank branch renovations EllisDon is doing across Canada, he says.
“We’re removing ceiling tiles and scanning spaces to capture existing mechanical systems from which we’re developing as-built CAD work quickly, feeding the consultants so they can complete the design process, and expedite the start of construction.”
Strong says the rising popularity of 3D scanning is partly because of dropping hardware and software prices but also due to the growing number of specific-use systems with user-friendly interfaces.
At EllisDon, a scanner with a short range (about 120 metres) that scans quickly is used to scan interior spaces up for renovation. Typically, survey points are set at about 25 metres apart with a laser scanner called Focus3D by FARO, he says.
In a typical scenario, Strong’s department will scan the existing conditions of a building at the first stages of a proposed design and a BIM or CAD model will be developed from the 3D scan. Scans are input into an online portal so the renovation’s design team can access accurate as-builts which include photographs of the area.
Consultants can go online and do a virtual walkaround of the project site, which allows them to work long distance without leaving their offices, he says.
3D scanning also allows for inspection of the tolerances of installed systems. A 3D model provided by the structural steel erector can be compared through scanning software against the actual site erection, for instance.
“If we see an issue, we can take steps to resolve it to prevent construction delays,” Strong points out.
Traditionally, Total Stations have been used in these situations, he says, but 3D scanners provide more information and they are “fast and accurate.”
It is also relatively foolproof, although it can be tricky for large buildings where many scans are required because the data points of each scan must be “locked into” all the other scans to complete the picture, says Strong.
Along with 3D scanning at the design phase, EllisDon uses it during construction to develop as-built geometry. For example, installed mechanical systems are scanned before walls are erected.
“We can incorporate that into a Navisworks software file to give to the owner at the end of the project,” adds the virtual construction director.
The contractor is doing that at the Calgary International Airport where the entire network of hydronic heating tubes is being scanned prior to concrete slab pours to create a record of precise locations of every line to capture as-built information, says Strong. Measurements produced by hand, by comparison, are imprecise.
3D scanning is also suited to quantity surveying such as when existing topography needs to be captured prior to excavations.
Strong adds for insurance claims on damaged buildings with no as-built drawings, scanners can prove invaluable.
“If damage areas are inaccessible without a zoom boom or scaffolding, you can shoot the area with a scanner from the ground, bring it back to the office and collect your measurements,” he said.
The first time EllisDon used scanner technology was about eight years ago when it retained a consultant at the new addition to the Art Gallery of Ontario. Among other things, structural steel tolerances were checked on 3D scans of the glulam structure of the façade against the CATIA model.
At the time, the cost of scanning equipment was prohibitive for most builders, says Strong. Today, however, dropping prices put larger builders into the game with systems like Focus3D costing about $50,000.
The technology is paramount in managing risk on renovations, he says. “It’s critical to start from accurate information and this technology does that really well.”
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