Comment
The black art of laser scanning Building BIM-ready models from point cloud requires considerable manual construction, a skill level developed by working with and understanding fully the nature of the data. Ploughman Craven’s Peter Folwell explains.
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he profile, awareness and capabilities of 3D laser scanning have grown exponentially over the last couple of years. With the UK government mandate to deliver level 2 Building Information Modelling (BIM) by 2016 for publicly funded work, and an increased market trend towards refurbishment and retrofit, there has been a greater emphasis on the use of 3D laser scanning technology and the ability to deliver BIM-ready models of the existing environment. There has been an increased awareness of the benefits that this powerful technology can bring through the whole project lifecycle — from the ability to collect a lot of up-front accurate information for feasibility studies and planning, through to wall alignment checks at demolition, clash detection, design comparisons and monitoring during construction. Other advantages include an accurate solution for offsite manufacture, pre-fit out surveys and asset recording for facility management. One result is an increase in the visibility of scanning manufacturers extolling the virtues of their products and ease of use for all, plus a surge in development of software abilities to handle large volumes of point cloud data. This, coupled with a decrease in costs and barriers to entry, is starting a possible trend away from the traditional surveying expertise route for delivery. The emergence of 3D laser scanning opens up other professional’s minds to the benefits on offer but without a full understanding of the complications, limitations
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November / December 2014
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About the author Peter Folwell is a director at Plowman Craven with responsibility for survey deliverables within the BIM environment. He is involved in Survey4BIM and a founder of BIMnet.
and considerations that need to be taken fully into account, success can be limited. There is an increasing number of users in the market, but many have limited experience and understanding of the full range of operational issues and what needs to be considered and addressed in order to achieve accurate and useable information. Plowman Craven has been associated with 3D laser scanning technology for over 14 years now, both utilising it and helping to develop it. In recent years, we have completed numerous high profile BIM associated projects within different market arenas, delivering both laser scan data and BIMready models. We are now in a position where we have a highly experienced understanding of the full technical applications, workflows required, issues and a comprehensive catalogue of lessons learned. 3D laser scanning technology provides a number of considerable advantages and benefits when collecting data in an existing environment, particularly in complex, architecturally challenging and safety restricted situations. Collecting data rapid-
ly, in 360 degrees, with speeds of up to 1,000,000 points a second provides an instant record and a complete data set in order to extract 2D information or build BIM-ready models. However, it is a line of sight technology and, contrary to popular belief, it does not go through walls or ceilings. It sounds a great solution but what needs to be considered in order to achieve the desired outcome?
Right tools for the job There are many scanners on the market at different cost prices and capabilities. These could be static, airborne, vehicle mounted and even handheld. It is critical to understand what each can deliver and the most appropriate use. The right choice of tool can have a profound effect on the project cost and also accuracy of the data.
Quality control The real black art of 3D laser scanning is knowing what is likely to be going on ‘under the bonnet’ and understanding how to achieve optimum performance and the required results. Angles of incidence: Geometric considerations and location to reduce glancing Surface reflectivity: Different surfaces and conditions produce a varied quality Scanning speeds: Gauges the intensity and volume size of the point cloud Quality settings: Filter settings that influence the level of noise in the data Target ranges: Consideration of distance www.AECmag.com
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