Low-fidelity information. After decades of investment, engineers, construction contractors, suppliers and asset owners still find themselves plagued by information about their existing assets that’s not
complete enough, detailed enough or timely enough to support high-confidence, low-risk decision making.The culprit? Gaps within solutions for asset design, management and modification. Gaps between solutions. And gaps in engineering, fabrication and construction processes.
Where are these gaps, and what can project managers and asset owners do about them?
Information fidelity degraded by gaps between as-designed and as-built
The biggest penalty in information fidelity is exacted by gaps between the domains of as-designed and as-built – specifically the disconnects between:
• Existing conditions and new design work
• Design and fabrication
• Design and construction
• Construction and design reuse
• Design and operations and maintenance
In a word, gaps between the digitally modeled and physically measured worlds.
Of course, these gaps are not only technological but also embedded in work processes and organizational structures. But one thing that has made them so persistent has been the lack of effective tools to bridge them.
Breakthrough of laser scanning – bridging the digital-physical divide
This is why terrestrial laser scanning is far more than just another design tool – it seeks to close the gap between computer-generated digital design models and sensor-based digital capture of existing
By enabling sensor-based measurement to inform computer-based abstraction, laser scanning is helping contractors and owners connect the nominal, idealized world of computer-aided design and engineering with the physical realities of fabrication, construction, operations, maintenance and modification.
Of course laser scanning is not the first technology for digital capture of physical assets. But its breakout success is because it is beginning to allow digitally captured physical conditions to be integrated with 3D and 2D modeling environments quickly and accurately enough to usefully
inform design work.As-designed is never as-built is never as-maintained
Our research documents that laser scanning is driving a leap forward in fidelity of IT-based asset creation and modification processes. Primarily, of course, it does this by enabling design in the context of existing conditions.
Why is laser scanning needed for this? Isn’t the design model, properly maintained and updated, the highest-fidelity representation possible of the as-built asset? Many design system vendors say so. Some owners do use CAD models and associated databases in managing the facility. However, for contractors engineering modifications to an existing physical asset, there are aspects of reality that a 3D CAD model, even when perfectly maintained, will not reflect.
One reason lies at the heart of the difference between computer-based abstraction and sensor-based reality capture. Built assets inevitably behave physically in ways that CAD technologies are ill suited to
represent. Never mind the expense and difficulty of maintaining as-built CAD models, bridges flex, pipes sag, equipment is installed with skewed orientation, walls go out of plumb, the earth subsides – such changes are difficult if not impossible to represent realistically in a 3D CAD model. Field validation and verification is an absolute must; the issue is how to minimize the cost and schedule impact.
Tying design to fabrication
Another digital-physical gap that incurs significant schedule and cost penalties exists between design and fabrication. Misfabricated pipe and equipment is a vexing problem that has persisted despite improved capability and output of design systems in this area. Today, practitioners are looking to bringing laser scanning to bear on the problem.
The work process goes like this: scan tie-in locations on the job site, then survey/scan equipment and fabricated pipe before shipment to the site to ensure correct fit.
This technique has particular value in situations where rigging costs are high, for example where a crane or other expensive equipment will stand idle if fabricated product turns out not to fit. In addition, laser scanning can help lower fabrication costs by enabling contractors to reduce the number of field fit weld operations.Tying design to construction
The gap between design and construction is also being narrowed by laser scanning. Used for field verification of construction work, laser scanning can monitor not only progress and schedule adherence but also construction accuracy, and thus help owners control payments to contractors. We believe laser scanning will also be used as a construction and installation sequencing tool, due to its ability to support clash detection and avoidance.
Of course the field rework that laser scanning helps reduce is driven not only by errors but also by project scope changes due to exogenous factors such as a shift in demand or other market conditions for the owner. Terrestrial laser scanning can help contractors be more responsive to changes that arise mid-project. For example, by providing rapid documentation of construction and field conditions to date, laser scanning can help contractors perform options analysis and explore the impact of changes on schedule and cost.
Another example is where a contractor’s purchasing department decides to switch suppliers for equipment or materials. While functionally equivalent, the new product may have somewhat different
geometry than what was originally specified. Dimensional control is sometimes a casualty in low-bid situations. Laser scanning can help designers be more agile and flexible in responding to such changes.
As-built asset capture for design reuse
Capturing as-built conditions of new construction for use in subsequent projects is yet another gap we expect laser scanning to bridge. We believe the technology will become widely used in cases where the same design is going to be constructed multiple times. Practitioners are starting to investigate techniques for scanning the first completed instance of the facility, then updating the as-designed CAD model with as-built conditions. The vision is to automate the capture of experience and knowledge gained on the first project, so that subsequent projects can be executed more rapidly and with fewer errors.
Construction claims litigation
Some also expect laser scanning to be useful in litigating construction claims. The approach envisioned is that laser scanning will remove most ambiguity about site conditions before, during and after construction. By comparing these scans, claimants or defendants will be able to prove exactly what work was done to the site. Also envisioned are comparisons between as-designed (documented in the 3D CAD model) and as-built (captured with laser scanning) to prove the scope of changes executed during construction, and thus document claims regarding change fees.Futures – digital-physical fusion?
Notwithstanding all this, much remains to be done. The linchpin of laser scanning’s success is its speed and fidelity in making existing-conditions data available to inform design work. But today’s
technologies are still not all that practitioners want them to be. For developers of existing-conditions management software, a goal that practitioners are asking for is to make it still easier to bring laser scan data into the design process – ultimately, to make it transparent whether a user is working with captured data or generated data.
A starting point would be tight integration between all leading laser scanning software products and all the major CAD design systems, instead of the patchwork facing practitioners today. The obstacles
include business model conflicts – for both sides – as well as resource constraints at many point-cloud software developers. So we expect progress, though in fits and starts.
In future, we believe laser scanning technology, and how it’s deployed and used, will evolve to enable existing-conditions capture on demand, at least in some industries. Some offshore platform managers envision a time when scanners are both rugged and inexpensive enough for several to be permanently mounted on a platform. With this, existing-conditions “snapshots” could be taken remotely, avoiding much of the need for offshore travel. We expect similar visions to emerge for using the technology in onshore plants and other built assets. In such cases, laser scanning could well be combined with complementary sensor technologies such as RFID (radio frequency identification) tagging of
equipment and components to move physical assets a long way toward being, in effect, self-maintaining.
Environments that transparently fuse digital (modeled) and physical (measured) data, able to access existing conditions captured on demand, could be the magic key that design system providers have long sought to make their technologies a practical mainstream tool for operations and maintenance, as well as a preferred choice for revamp and retrofit work.
This material is excerpted from Spar Point’s just-released publication
Capturing Existing Conditions with Terrestrial Laser Scanning: A Report on Opportunities, Challenges and Best Practices for Owners, Operators, Engineering/Construction Contractors and Surveyors of Built Assets and Civil Infrastructure