LEE MCDOUGALL from AHR Building Consultancy pierces the technical mystique still surrounds BIM and explains the uses and abuses

Rail use is going through major changes, with technologies such as mobile ticketing changing the way that customers use stations and necessitating refurbishment and alteration work, and with the ongoing drive to capture lost revenue through new ticket barriers. There is much to be done in terms of upgrading and alteration and TOCs will surely welcome any new technologies that make these tasks easier. But wading through the BIM-wash and tech-talk can feel like a task in itself.

BIM (building information modelling) is almost mainstream now, although still often misunderstood and at times a little daunting for station owners working at a fairly small-scale, whilst other technologies such as the use of drones in survey work are only just finding their feet, and if not used wisely can present unique problems for the rail sector. How to sort the wheat from the chaff? Or the BIM from the BIM-wash?

Tools not toys
Certainly we should make the most of the tools and technologies available to us – from laser scanning to BIM and from drones to GIS (geographic information system) – but there can be a tendency to get carried away with tech for its own sake: remember the very early days of BIM and the way that laser-scanning can sometimes seem to be used purely to create whizzy graphics? Not that impressive graphics don’t have uses in certain situations but TOCs and station owners, with a firm eye on budgets, will be keen to ensure that technologies are only used when they have real-world benefits and only as appropriate for the task at hand. Because of this wise reluctance to embrace the new for the sake of it, it is understandable to be sceptical. What’s needed for firm decisions is a genuine understanding of the particular benefits that various technologies (alone and in combination) can provide.

As noted, BIM is already fairly commonplace, indeed compulsory on public projects since early 2016. Yet its value for smaller-scale projects is perhaps less well known, which is a shame because so much of what needs doing is at the smaller-scale. It is also not widely recognised that BIM models are capable of slotting into each other to form a bigger picture model over time so that BIM adoption can be taken at a manageable pace. In particular for TOCs and station owners there is also value in the fact that, in conjunction with laser scanning, BIMs can be produced for existing assets, a boon when working with existing and historic stock.

Maximising efficiency – minimising disruption
The appropriate use of technology can produce significant efficiencies in both time and budgets. It is already well-known that BIM’s highly accurate scenario modelling means that tolerances can be very accurately calculated. Drones, too, can deliver hugely reduced timescales (and costs) by eliminating the need for scaffolding / cherry pickers. This in turn minimises disruption – always important but especially so for busy stations. In addition for outdoor surveying, using a drone rather than cherry pickers means we are far less at the mercy of the elements: should the weather turn bad, we can reschedule the survey for another time or simply retake the shots at very little cost or inconvenience.

Of course there are factors unique to rail that mean we should take special care with drones – for example tracks often pass very close to residential areas which can cause issues of perceived intrusion of privacy – there are also the dangers associated with overhead cables, not a typical factor on a standard building site, and of course with live tracks and trains themselves. However all of these factors should be covered with a registered‘drone pilot’ who by law will have to assure a safe,accurate flight path and get relevant permissions, so people should not be put off by these issues and drones, in conjunction with cameras and other technologies, can have impressive benefits.

Accessibility, accuracy and context
Drones can ‘reach the places others can’t’, which makes them particularly useful in larger stations or where data is needed about a roof (or otherwise inaccessible areas). This accessibility in turn enhances accuracy: a drone can get very close to the fabric of a building, face-on, hence avoiding the parallax effect, and since images (when used in conjunction with a camera) are captured well above the human eye line, blind spots are also minimised – both of which eliminate distortions.

The true value of this accuracy really comes into play when a drone is used in conjunction with laser scanning: by attributing RGB colour values and ‘draping’ these photographs onto cloud point data, we can tie down the precision of the images to extract highly accurate measurement data from which to create 3D models. Though not always necessary (and certainly not for its own sake – a set of asset condition surveys may not need this level of accuracy) – where a higher level of detail accuracy is required this combination of technologies can be invaluable.

Adding the use of GIS into the equation also provides us with valuable information about the location and orientation of an asset. This can tell us for example how a building is likely to weather over time.

The key is always to tailor the use of technologies to the scale and needs of the project. At Euston, for example, the complicated relationship between the levels of the concourse and the ramps necessitated a 3D Revit survey model, which AHR achieved with the pioneering ‘scan-to-BIM‘ procedure. And because we undertook data gathering over only a few overnight sessions, there was minimal disruption to the workings of this busy station.

At Leeds meanwhile our work on the new South Entrance creating a point cloud survey included surface curvature analysis of the building’s intricate geometry,enabling the team to identify the most efficient shape of the external skin and to rationalise the structure to produce a profile that could be repeated, reducing fabrication time and cost. The new entrance is an attractive addition to the regeneration of the now hugely popular South Bank of this thriving city. Our team have also worked at Leeds station’s other concourses gathering data with a view to increased capacity down the line.

Technologies can also be invaluable at a more lowkey scale – for example at Bolton Interchange where there were concerns that new facilities might obstruct light. Through the use of BIM we were able to track the sun and calculate the right of light (as well as noise levels) allowing us to get on board a notoriously difficult stakeholder: the public at large.

Attracting investment / getting stakeholders on board
In fact bringing reluctant stakeholders on board or attracting investment is another benefit of BIM. While the central point of BIM is that it is data-rich – rather than just a simple visualisation tool such as CAD – this combination of data and ‘graphics’ can nonetheless be very beneficial in enabling people to envision a broad range of possible permutations at the very earliest stages, thus maximising certainty.

These data-rich BIM models are also useful long after build as a tool for asset management. While we are only just beginning to explore the long-term potential of BIM models for facilities management purposes, already it is clear that managers of large estates with multiple assets are building up a collection of smaller BIM models over time which bring together enormous quantities of useful data. BIM compatible FM software can offer huge potential value in BIM long after a project closes.

Whether a small-scale station remodel for revenue collection purposes, an extension to a station to accommodate an increase in customer numbers, or the redevelopment of dated assets as part of a broader project, technologies have their part to play and their use can be scaled-up or down dependent on the needs of the project. These are exciting times for rail but there is much to be done to ensure station facilities are up to standard. We will go faster and further if we embrace this wave of new technology.

Lee McDougall, is director, geomatics, at AHR Building Consultancy