INNOVATION May-June 2015

Above: Point cloud data captured by a long range TLS from a single setup near Prospect Point in Stanley Park,Vancouver, BC.

Right: The complex layout of overhead lines captured near the Commercial Drive SkyTrain Station in Vancouver, BC.

Laser scanning offers an exceptional level of detail, regardless of geometrical complexity. Consequently, the amount of data captured is enormous. The computing power and data capacity are less of an issue today than just a few years ago. Furthermore, many mainstream CAD software packages will now accept point cloud data directly. As the TLS technology continues to improve, computing power and software will continue to play catch-up. Benefits Accurate Record Documentation Laser scanning data delivers a complete picture of the exist- ing conditions at the onset of a project. Historical drawings are often inaccurate, missing, or damaged. If as-built drawings are available, they may not be representative of the present day con- struction due to improvements made, geological and structural settlements, etc. Unlike the conventional method of a surveyor’s total station, laser scanning collects a wealth of data, from which information can be extracted now or in the future without the need to revisit the site for additional field work. Construction Management Laser scanning can also be performed on an interval basis in areas of interest for monitoring construction progress or for validating the work performance. It is gaining popularity in confirming critical items, such as floor flatness and floor-to-floor utility alignment, before the work proceeds to the next step. From the point cloud, virtual computer models are generated for conceptual designing and for simulating the transport of large machinery through tight corridors for clash detections. Reduce Rework Costs Some may claim that conventional measuring methods (e.g., tape, total station, etc.) are cost-effective and quite adequate for what they need. These methods are completely different from laser scanning and would work well as long as the assumption of linearity holds true (e.g., no curved objects). In larger construction projects, such an assumption introduces the opportunity for clashes during design and throughout the construction phase. Invariably, CAD and Revit drawings would not conform to actual construction and create prefabrication issues. Laser scanning reduces rework costs. Reduce Liability Some may also claim that there is no budget allocated in the project for laser scanning. In actuality, the cost of laser scanning

pales in comparison to the average cost of change orders. Laser scanning will not completely eliminate change orders, but it could potentially reduce exposure to liability. Major public construction projects as a rule of thumb will have 3 to 4% of the total budget allocated for change orders. For smaller projects, one literature suggests that a $5 million dollar project would typically experience a change order of $250,000 to $400,000. An investment of about $25,000 could avoid the bulk of the change order costs plus any schedule delays. Multi-Disciplinary Usage Point cloud data is not limited to any single task oriented group. Rather, the information is shared across multi-disciplinary groups, such as mechanical, structural, civil, and electrical. The power of 3D visualization has enabled effective communica- tion between staff members through web portal services from a centralized data source. Safety In addition to efficiency and accuracy, safety is another key consideration. The introduction of TLS means that field technicians can now be positioned in a safer environment with less environmental exposure to busy traffic, industrial noise and chemicals, while reducing the inconvenience to a client’s operations. Typically, TLS systems use a visible light Class 1 or at most Class 2 laser, where the aversion response limits the exposure to no more than 0.25 seconds. Most laser pointers use visible light Class 2 laser. General Work Flow Generally, there are four main production stages in a laser scan- ning assignment: Data acquisition – a set of point cloud data is collected at each scan station. Due to line-of-sight requirements, multiple scan stations are normally required to eliminate blind spots and to increase the detail level. Registration – multiple point cloud data sets from various scan stations are “stitched” into one large point cloud and cleaned

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