Using the latest techniques to monitor railway infrastructure

Simon Abbott from Network Rail and Matthew Bray from SatSense discuss the technology driving earthworks asset management

Imagine knowing how much the ground was moving around your line, embankment, station, bridge or tunnel from the comfort of your desk.

It was the vast untapped potential of highresolution ground movement data from radar satellite, using a technique known as InSAR, that was the calling for Matthew Bray to take up the post of Chief Executive Officer of SatSense.

Matthew Bray

InSAR, or interferometric synthetic aperture radar, is a remote sensing technique which uses multiple radar images to detect changes in surface deformation down to rates of 1mm/year.

The InSAR dataset is automatically updated every six days and stored for online access by customers and partners. The nature and frequency of this data means it may be possible to identify and highlight areas of the railway that are subject to progressive movement, enabling a more effective treatment of risk by Network Rail. This could lead to less disruption and improved passenger safety.

“We are passionate about helping people to understand what’s happening on the ground, and structures on the ground,” said Matthew, who is still amazed at the broad appeal of such a niche technology.

“In essence we provide information from satellite data to help people figure out how their area of interest and structures on the ground are moving. The use of satellite data means we can cover large geographic areas such as entire countries and continents.”

Freely available data

The raw satellite radar data is freely available from the European Space Agency’s Sentinel-1 satellite constellation.

SatSense’s know-how coupled with recent technological developments means it is now possible to apply this data to user cases such as rail, highways and utilities.

It has caught the attention of Network Rail. The organisations are working together to determine how the data could help in the management of the organisation’s 190,000 earthwork assets, which includes the likes of slopes, embankments and cuttings – excavations in the ground composed of rock and soil.

“Earth observation techniques are something being talked about more and more today,” said Simon Abbott, Network Rail’s Professional Head of Geotechnics.

“That’s a good thing because there’s an opportunity there to change the way that we look at infrastructure within the realms of what is practicable from those types of technologies.”

Using the InSAR technique, radar images with a standard resolution of 4 by 14 metres can cost effectively cover tens of thousands of square kilometres, making it suitable to monitor ground movements across a large range of spatial scales.

“Rail is an ideal candidate for our technology and the team have been talking to Simon at Network Rail since the very early days of the company in early 2018,” said Matthew, who joined SatSense as CEO just as the country went into lockdown in March. “Our technology is well suited to rail because it is remote sensing, covering large geographic areas that include the rail corridor and the adjacent land, without having to send staff on site – i.e. fewer boots on the ballast. Artificial reflectors can be installed where natural signals are insufficient.

“We’ve struck a good relationship with Simon and he’s put us in touch with his team of geotechnical and mining engineers. Working alongside Simon and his team we can identify the information that is of most benefit by applying our bespoke algorithms to the raw InSAR data.”

Open and honest

Simon, who has been at Network Rail since 2006, has praised the open and honest conversations held between the organisations.

“Some of the challenges that the industry have in terms of earth observations is that they don’t always think they pitch the capabilities back into the engineering sector in a way that is a solid reflection of how they can be used by the industry,” said Simon.

“One of the refreshing things I’ve had from SatSense is just an honest appreciation of our business challenges and how its techniques could assist us but also where the techniques aren’t going to be able to assist us. It’s trying to look at our business problems and working with us.”

Network Rail’s earthwork portfolio is as old as the railway itself – with most of the infrastructure slopes more than 150 years old.

This is why such importance is placed on the network’s earthworks and their condition.

Its team of specialist geotechnical engineers use examination data and monitoring results to determine the appropriate interventions at the right time needed to help minimise risk, damage and disruption.

“The cost of the construction of slopes is quite expensive and we’ve got a very diverse asset base across all parts of the UK and all sorts of different terrain and topography,” said Simon. “We have a whole load of existing business processes that are fairly good, but as technology advances we are always looking at how we can strengthen our existing controls to make them more effective.”

Regional deformation

Simon continued: “Techniques that are coming into the frame more, such as InSAR and earth observations, start to give us that opportunity to look beyond the boundary fence at more regional deformation. This could be in response to ground water changes or through large ground displacement and movement, and that is all really positive – it’s information that could go into our existing processes to make better decisions.”

By examining geotechnical data and the results of monitoring instruments, Network Rail teams can determine the appropriate interventions needed to help minimise risk, damage and disruption.

Matthew said: “I think our technology comes into its own for detecting more subtle shifts over a period of months and years. It is updated every few days – but it is days, so we’re not in the business of detecting rapid or instantaneous events. “But what we can do is detect even very small movements that can be precursors to significant geotechnical events or just areas that need further investigation.

“There might be an historic mine or a spoil tip, or someone on land adjacent to the corridor engaged in construction work that may have an impact on the railway. You’d be surprised what we can see with the data.”

The potential benefits of the technology of SatSense has already been put to good use in the railways. The company processed Sentinel-1 data over a site on the Dover to London mainline near Folkestone, analysing the data from four different tracks to build up a more complete picture of the deformation.

Network Rail was able to connect specific features identified in the SatSense results to ground-based observations.

Operational consumption

Matthew said: “I think we’re still a little way off operational consumption of the data, but what we’ve hopefully done is demonstrated a really honest appraisal of what the data is and isn’t capable of.

“We’ve outlined a way of further exploring the potential, and Simon and his team have given us some direction into how we need to tailor that offering and make sure it is easily consumable and easily understandable by people.”

Simon said: “It is about looking at how we take the data and make it so that it is useful in an efficient and effective way to those who are looking after the infrastructure at a more tactical level at a regional basis.

“But we have a limited amount of funding and we want to make the best use of that funding, so any data that can come in and inform us and maybe challenge or reinforce where we are planning to investigate, that is only a good thing.

“I think the challenge for us is to kind of start to work up some locations to really try and test the water in a robust process to see whether this is not going to confuse those at the coalface so to speak.

“It needs to bring value in an effective and efficient way for our evaluation process.”

The conversations come as Network Rail has recently published its Environmental Sustainability Strategy – looking at the steps to be take over the next 30 years to see rail powering Britain’s green economic recovery. The document details the vision to serve the nation with the cleanest, greenest mass transport, with four core priorities:

• A low-emission railway

• A reliable railway service that is resilient to climate change

• Improved biodiversity of plants and wildlife

• Minimal waste and sustainable use of materials.

For us to be a critical service for transportation, we need to have focused activity in areas that we recognise have a particular vulnerability and target investment accordingly

Simon said: “There is always a drive to do more with technology. We need to make the railway fit for the future and we’re going to be watching the Environmental Sustainability Strategy with interest as to what does that mean for infrastructure investment as we move into future control periods.

“This is particularly around the kind of strengthening activities to physically make the asset more resistant to adverse and extreme weather. There will be some interesting times ahead. We’ve all seen the impacts of the likes of excessive rainfall and flooding and how that can bring parts of the country to some challenging positions. For us to be a critical service for transportation, we obviously need to have some focused activity in areas that we recognise have a particular vulnerability and target investment accordingly.

“As the technology develops, we are able to monitor the performance and condition of our infrastructure more closely and accurately, putting us in an even better position to handle the consequences of climate change which is increasing the frequency of extreme weather events.

“The space sector is a real growth area for the UK. Only last week we heard how the Leeds region has secured funding from the UK Space Agency to help spearhead a national programme of technological revolution, through regional space hubs” added Matthew. “We can see that continued support of space technologies will not only improve safety, reliability and value for money for customers, but will benefit the UK economy as a whole.”