Building information modeling (BIM) has been hogging the spotlight recently.
Yet the focus has been, understandably given government targets, on its use in new-build projects. But laser survey equipment could be set to change all that.
At a basic level, BIM refers to those systems that allow for the collection of inform ation about a building, such as the dimensions and performance metrics on individual components, and information about materials, with presentation of this data for analysis, usually via ‘dashboard’ software on a PC.
This wealth of information can, in theory, be used to run a building far more effectively, with a higher degree of control, accuracy and certainty. In other words, a facilities manager’s Holy Grail.
The government has confirmed its faith in the idea by making it a legal requirement for all public sector buildings from 2016 and it has become standard practice for many private projects, too.
However, the most common application has so far been for structures still on the drawing board. BIM systems are powerful tools for architects and planners looking to design within specific criteria. But, until now, it has proved more difficult to apply the logic of BIM to pre-existing structures. If all the elements of a build are already in place, the argument goes, any adjustments made on the basis of recommendations gleaned from the computer model, necessarily, could only be fairly minor.
And since it’s widely accepted that the vast majority of the buildings that will exist in 2050 already exist today, this presents a serious limitation of the idea of ‘modelling to improve’. Laser surveying could provide the means to bridge this gap. Most will be familiar with the sight of surveyors using strange boxes mounted on tripods to take measurements of a site. A new generation of scanners uses similar technology — laser beams — to take millions of measurements of a building’s exterior and interior. Using computer software, users are able to create a ‘virtual’ version of the site, which is navigable, with the data it yields much like a high-tech version of Google’s ‘street view’.
Built in 1093, Durham Cathedral is considered a masterpiece of Norman architecture. One of the most complete examples of the style in Europe, it is now protected as a UNESCO World Heritage Site. Recently, a laser survey was conducted in order to aid restoration work and to gather a ‘snapshot’ in time of the venerable building.
A survey team conducted a 3D laser scan over the course of 10 days. Due to the site’s regular public use, most of the work took place after hours. The team used a Faro Photon120 phase-based laser scanner and all scans were carried out to a very high ‘point density’. Colour photography was also used.
Over 250 scans weremade and processed by the scanner’s on-board software package, which allows for automatic target extractionand registration making iteasier to process and manage large projects.
The images were then ‘orthorectified’ — adjusted to remove the effects of tilt or perspective — and created in monochrome and colour at 1:20 scales. At this point, the images are usable in a software package such as Autocad, that is ready to divulge their data for the purpose of BIM.
Scanning up to one million points per second and accurate to less than a millimetre, the systems are causing considerable excitement. Striking images show once-familiar facilities in a whole new light; structural flaws once invisible to the naked eye, such as narrow cracks are now displayed in brightly coloured, hi-resolution imagery.
The applications for this technology go beyond just mapping buildings. Aircraft hunting for enemy submarines during the Cold War carried similar equipment, which was sensitive enough to detect the minute differences in the sea level on the surface above a submerged vessel. Today, archeologists hunting for buried remains are fitting laser cameras to aircraft, so that whole swathes of territory can be mapped within minutes. The images can reveal structures that weeks of digging could not hope to alone.
Even Hollywood uses laser surveying. Sets, props and even million-dollar fee actors themselves can be scanned and manipulated by computer systems at a later date. This information can be combined with motion capture technology to create amazing effects. Not only that, ‘scanning’ an actor serves as an insurance policy in case of loss or damage to that individual, which could compromise the filming schedule.
Drawbacks
Laser scanning is undoubtedly a step-forward in site surveying. But there are several issues with the process that prevent it from being the silver bullet many hoped it would be. Fundamentally, laser surveying simply isn’t right for every surveying application. Experts still use the less-sophisticated ‘total station’ equipment (mentioned earlier) to get basic, solid information about a site, such as dimensions.
The problem with laser scanning is precisely its strength — it captures a huge amount of data. On many sites, the vast majority of this data will never be used. This data is also very unwieldy, being held in data files of many gigabytes, which only trained individuals can make sense of.
Also, as the Durham Cathedral case study shows (see side panel), it’s not simply a case of scanning a building, uploading, and then, wham, it’s ready to be used in a computer BIM programme. A labour-intensive process is required for an expert to make the data usable; ‘ghosting’, where miscellaneous unwanted objects such as raindrops or passing cars show up in the data, needs to be painstakingly removed. The fact that there are multiple software platforms on which to run BIM makes things even more complicated — the output data may not necessarily work on your BIM management system.
All in all the picture is, so to speak, far from clear. The technology does provide some evidence to suggest that laser surveying could be a major contributor in expanding the potential of BIM.
However, it would be rash to assume the process is appropriate for all situations. FMs would do well not to let this emerging technology blind them to other surveying options.
