LiDAR systems

The Road to Recovery: Using Mobile Laser Scanning for Highways & Rail

In by Nicola Dupont

Any disruption to transport networks not only infuriates travellers, but it also has huge cost implications for operators. However, as our Research & Development Manager Dr Neil Slatcher explains, recent advancements in LiDAR systems (Light Detection and Ranging) technology are already helping to improve Intelligent Transport Systems.

The effects of climate change have long been a consideration within the transportation industry. This year has seen its fair share of landslides, structural collapses and surfacing issues impacting on services across the world. While in the past identifying problem areas would have been labour intensive, the sophisticated use of laser technology can help recognise unstable situations that are the precursor to rapid failure. The recent landslip in Watford is a prime example.

Two people were injured when two trains collided after torrential rain caused a landslide near Watford Junction in September. While the line owner, Network Rail reopened the affected tunnel after three days, more could possibly be done to highlight problem areas and prevent future incidents.

tunnel-train

rail network

Network Rail’s ‘Railway Upgrade Plan’ represents the biggest programme of rail modernisation since the Victorian era and while much of the infrastructure in other countries may be younger, the changing climate continues to affect ITS across the world. Advances in technology now allow us to gain greater insights into how our services can be improved and how necessary maintenance can be scheduled without added disruption. By observing changes in the landscape in 3D, we can now begin to identify areas which are at risk. Incorporating the use of LiDAR systems allows potential issues to be detected early and technical intervention teams to be deployed before or after an incident, allowing restitution work to be carried out more quickly and efficiently.

Traditionally, surveying rail infrastructure has meant using in situ sensors, which provide constant measurements of known unstable areas. The downside with this method is that only known problem areas are monitored. Mobile scanning provides a comprehensive scan whilst attached to a train or backpack, capturing everything in the path of the unit, allowing for scrutiny of an entire track or network.

The advancement into mobile laser scanning holds great possibilities due to the sheer extent of the area able to be captured in one scan – up to tens of kilometres a day. By combining a high accuracy survey-grade inertial navigation system and two LiDAR scanner heads each measuring 550,000 points per second, the technology captures an extremely high resolution dataset with achievable accuracies to within 10-20mm.

The following video shows the Silver Jubilee Bridge in Runcorn. Created with ROBIN +PRECISION in DRIVE mode, the data took only 10 minutes to collect and has an accuracy of around 7mm.

In France, engineering company Groupe Fit Esic has used 3D mapping technology to survey hundreds of kilometers of the French rail network for operator SNCF. The team used a rail-mounted StreetMapper LiDAR system with two high accuracy lasers that offer a 360° field of view and high precision mapping to a range of 300 metres, which enabled engineers to build a detailed 3D topographic map of the track and its surroundings. This provided length data and cross profiles, as well as detecting potentially dangerous objects and vegetation near to the track, which were measured to determine clearance from the line and passing trains.

FIT-ESIC-Railway-16The data has then been used to carry out infrastructure inventories and clearance analysis as well as identifying and prioritising maintenance needs and contributing to the country’s Smart City ambitions.

This type of technology also dramatically increases the safety and efficiency of survey personnel. In comparison to static terrestrial laser scanners, mobile laser scanning units can be mounted to trains and other vehicles as well as backpacks, allowing automated scans to be completed without dedicating a large team to the job. This means staffing costs can be reduced, freeing team members to work on other projects.

In regards to time savings, Fit Esic has been reported as saying that its use of 3D mobile mapping technology has significantly reduced time-to-delivery of surveying projects. Other reports suggest that mobile laser scanning allows projects to be carried out up to 80% faster than when using terrestrial scanners.

Pre-construction specialists Central Alliance operate emergency response teams on major landslide sites across the UK’s railways and continue to invest in LiDAR technology to assist in their work. They recently acquired a cutting-edge universal MLS (Mobile Laser Scanner), ROBIN.

“With the challenges of acquiring data in often difficult to access locations that pose a severe safety risk, gathering LiDAR data quickly and accurately becomes invaluable for this type of emergency work where an accurate representation of geomorphological features for assessing slope stability is key. When making assessments on a failing slope for example, we need to know exact information about the existing condition of the slope so that we can assess how it has failed, what the mechanism of failure is and how to tackle this in remediation. It helps immensely in this situation to have a detailed 3D model of the site which we can provide using ROBIN – the multi-platform laser scanning capability of the technology means that we can capture all required mobile mapping data on any site by driving, walking or flying over it.”

The Road to Efficiency

The use of LiDAR has increased dramatically over the last 18 months with laser scanners being used in the development of autonomous vehicles. When positioned on the top of a car, these smaller units can scan around 60m in all directions, producing an accurate 3D map of a vehicle’s surroundings. This allows other sensors to assist the vehicle in navigating obstacles in real time, but before driverless cars hit our roads, all of our cities, towns and highways need to be mapped in great detail to include barriers, traffic lights and street furniture. By scanning every centimetre of public infrastructure, companies like Uber and Google are creating interactive 3D models which could help us towards an optimised, data driven, smart city culture, where different stakeholders can benefit from accessing the layers of information collected – rail assets, vegetation growth, road markings and bridge clearances.

In the US, one city council planned to spend around $1 million to evaluate its pavements and street furniture using a team of engineering students who would walk the route, evaluating the damage by sight. This process was estimated to take around a year. Using a LiDAR system, the scan and data processing would be complete in less than a month – including detailed visualisations to assist with monitoring high traffic areas most in need of regular maintenance. Road users, the transport sector, travellers and the local and national economy will all benefit from less congestion and delays caused by emergency repair work.

Having to dispatch emergency repair teams is costly for highways maintenance firms and diverts resources from other scheduled maintenance jobs. There is also significant impact on the economy, which relies on the highways being open and maintained. And while every set of roadworks causes some delays, with unplanned works there is little opportunity to facilitate adequate diversions or countermeasures, to pre-position materials and equipment or to pre-fabricate solutions.

Who’s Ahead of the Curve?

So, the question is, where is LiDAR technology already being used to improve our over-burdened transport infrastructure? The Road & Transport Research Institute in Lithuania provides a great example, where road authorities have easy access to mapping software, allowing them to keep on top of change on the highways and plan accordingly. The KTTI has been able to produce black-spot maps and other studies which highlight incident prevention, rather than reactive response.

Over in the Netherlands, land surveying and engineering company Geomaat also uses a StreetMapper system. The majority of the company’s work is road and highway survey based and it was looking for a solution to improve safety, accuracy and speed of delivery of data to their customers.

The StreetMapper system can be attached to any vehicle and allows scans to be completed at normal road speeds with no disruption or road closures necessary. The team at Geomaat has developed its own post-processing software to automatically identify the white lines and barriers on the roads and also round shaped objects, all visible on the resulting pointcloud.

geomaat_streetmapper_data2

This system has already been used on projects including planning the upgrade of the A50 between Ewijk and Valburg on behalf of the Rijkswaterstaat, a project to upgrade the runway at Johan Adolf Pengel International Airport and surveying and monitoring over 500km of highway in support of Lifetime Maintenance Contracts (LEM).

The results speak for themselves. In terms of cost efficiency, the new solution proved to be 50% cheaper compared with traditional surveying methods and by reducing the need to work through the night savings were made on staff overtime. Because the StreetMapper is attached to a vehicle, workers are not exposed to fast moving traffic and disruption to road users decreased because the roads no longer needed to be closed to perform highway surveys. Furthermore, the accuracy of the end data has greatly improved as it is presented in both absolute and relative terms.

No matter what area of transportation you are involved in, LiDAR technology can help to provide highly accurate data to assist with planning a safer and more cost efficient future.

To read more about Geomaat’s work with StreetMapper, have a look at our Case Study