Surveying a railway was once a labour-intensive activity that involved teams of workers using the kind of handheld tools employed by engineers for centuries.
But measuring the clearance of tunnels, the width of bridges and the height of platforms has become an altogether more high-tech job - one that involves using state of the art of 3D imaging programmes.
Network Rail, the state-owned group responsible for maintaining tracks across the UK, has for the first time utilised a three-dimensional scanner to precisely model railway infrastructure in Scotland ahead of the arrival of new trains onto the network.
The decision to survey the railway was taken ahead of the introduction of LNER Azumas, class 365s and class 385s, as well as the growing demands of freight operators.
Network Rail said this week the task of making sure that new trains actually fit on existing lines north of the Border had never been more crucial or time critical.
The Trimble GEDOScan system, which is operated by Network Rail’s team of absolute track geometry (ATG) engineers, has been deployed to collect detailed information about the track and surrounding features such as bridges, parapets, and platforms - quickly gathering precise, high-resolution data for use in track clearance assessments on structures and tunnels.
The new system was introduced in April and is already delivering higher quality scanning and modelling quicker and more precisely than before - with a relative accuracy of less than 5mm.
It also increases safety for rail engineers who now need to spend less time on the track to gather much more detailed data.
The scanning system has been used across the network to carry out general surveys for maintenance and monitoring - but also to assess the capability and suitability of specific routes to carry certain types of rolling stock, such as to review the possibility of introducing class 158 rolling stock on the West Highland Line.
It’s also been used to prepare for the introduction of High Speed Trains (HSTs) on the network between Scotland’s seven cities.
Surveys have also been carried out to assess the network for future freight capacity growth such as at Mossgiel tunnel near Kilmarnock, Drumlanrig, Blochairn and Duke Street tunnels as the railway prepares for larger and longer freight trains on the network and the benefits this could bring in terms of reducing emissions and removing vehicles from congested roads.
Graham Hutchison, an absolute track geometry engineer with Network Rail in Scotland, said: “Three dimensional scanning provides more, and more detailed information in a shorter time which reduces the need to be on the track; making it safer as well as more efficient.
“This system is ideally suited to tunnel surveys where irregular construction can make it difficult to locate the main pinch points.
The three-dimensional scan measures the full extent of a tunnel precisely in about a fifth of the time than it took previously.
“It can also be used for proactive monitoring to inform maintenance requirements and to better predict and prevent faults and to reduce disruption for passengers.”
Among the new trains on the Scottish network are the long-awaited Japanese-built Hitachi class 385 electric trains, which will provide more seats and faster journeys on the Edinburgh-Glasgow mainline.
The class 385 trains will become the backbone of the ScotRail fleet, replacing diesel class 170s that are nearly 20 years old, and eventually run on eight other Central Belt routes.