Written by Bernadette Ballantyne
Supported by the Satellite Applications Catapult
It was December 2015 and the UK was hit by a succession of devastating storms. Record breaking rainfall overwhelmed the country and rivers were dangerously swollen. Yorkshire, in the north of England was one of the worst hit areas. The intense storms led to higher and higher river levels breaching defences and in the village of Tadcaster something happened that no one was expecting….
Surging water rushing along the River Wharf became more powerful than the two-hundred-year-old Tadcaster Bridge could tolerate. To the disbelief of local people who had gathered on the riverbank it suddenly collapsed taking less than 30 seconds to crumble into the water.
Since this collapse on 29th December 2019, new research has been carried out that shows that data from satellites could have given owner North Yorkshire County Council prior warning that the bridge was at risk of collapse. With this data the catastrophic failure could have been prevented, and other vulnerable structures all over the world could be better protected.
Using Data from Space
Discovering that satellites could hold critical information to better manage and maintain structures began with research between the UK’s Satellite Applications Catapult and the University of Cambridge back in 2017. They took measurement of several bridge structures in the UK and they set about answering a simple question:
“Are satellites showing the right amount of displacements?” says Cristian Rossi, the Principal Earth Observations Specialist at the Satellite Applications Catapult who worked with researchers at Cambridge University to compare the data captured by satellites, showing how much bridges were moving, with actual movement on the ground.
“We found a very good match between the two measurements,” says Cristian which gave the team the confidence to ask an even more difficult question. Could they have predicted that the Tadcaster Bridge was about to fail?
Taking data from before the bridge collapsed the team compared its movement with 48 sets of measurements and determined that the rate of displacement of the bridge was accelerating. In mid-November 2015 it burst through the tolerable, expected range of movement of around 4mm to 6mm and it kept going. Two weeks later, by the end of November it was 9mm and just one month later the structure collapsed.
Morandi Bridge Collapse Warning
Cristian says that this shows satellite data can be used to predict bridge collapse, and Tadcaster is not the only failure that might have been predicted. On the 18th August 2018 the Morandi Bridge in Northern Italy collapsed during the middle of a busy Saturday killing 43 people. Less than a year later, in June 2019 a study between NASA, The Italian Space Agency, The Italian Environment Ministry and the University of Bath looked at satellite data for fifteen years prior to its failure. It showed that movement of the bridge had been accelerating since 2015.
So with these new insights, should we be harnessing satellite data more regularly to protect
bridges, and the public that use them? Researchers in Canada think so.
Daniel Cusson is a senior research officer with the National Research Council of Canada and can be found studying bridges in its Construction Research Centre. His group is focussed on creating better tools for the condition and performance assessment of critical infrastructure. This means working with Cristian at the Satellite Applications Catapult on using satellite data. “With Catapult we are developing a decision support tool to help bridge engineers make better decisions on the condition and performance of their bridge based on data. This is key information that they need, and sometimes it’s missing.”
Missing data. Not an ideal situation when there are 80,000 bridges across the country and, like other countries in the world there is no central database listing these bridges or their conditions. Information is kept at the local level.
Canada’s Ageing Bridges
With a design life of around 70 years, the bridges remain in service for a really long time and like in any country the condition of these bridges varies widely. Appropriate maintenance is therefore critical if the country is to avoid the disasters that other countries have experienced. According to Canada’s infrastructure report card a significant proportion of the country’s bridges are ageing and in need of urgent investment. 15% were found to be in a poor or very poor condition. That is 12,000 public bridges across Canada.
Although bridge inspections are conducted every two years Daniel says that tools for carrying out this work are limited and so to fill this void NRC with the Satellite Applications Catapult have created a new decision support tool for bridges known as Brigital, which in the long term could form the basis of a national assessment database.
“Brigital stands for bridge and digital,” says Cristian explaining that it uses a technology known as InSAR, Interferometric Satellite Aperture Radar to gather the information.
“By sending a radar, a sequence of radar pulses, as the satellite moves through its orbit, you can build up a really detailed picture of the scenes that you’re trying to observe on the ground,” explains Paul Febvre, Chief Technology Officer at the Satellite Applications Catapult. “
If a bridge is moving relative to the environment there will be a shift in the phase of the signal that comes back from the bridge. “We can detect those phase differences. And actually, you can detect the phase differences down to millimetres with the signal frequencies that we use for radar signals, so what you can do is if you’ve got a very solid structure you can measure the relative phase for different parts of the structure. And it gives you a really significant indicator of relative movement, which is a stress on the bridge.”
Millimetre accuracy from hundreds of kilometres above the earth.
Low Earth Orbit Satellites
In satellite terms hundreds of kilometers is actually quite close. InSAR satellites sit in a low earth orbit giving them the acronym – LEO. In Canada Daniel and Cristian used radar data from Canadian Space Agency satellites to begin monitoring the movement of bridges in Montreal. One of which was the 2.8km five lane steel truss cantilever Jacques -Cartier Bridge in Montreal. The bridge was built ninety years ago and crosses the St Lawrence River, linking Montreal Island with Quebec.
Using local information about the bridge Daniel and Cristian were able to create a numerical 3D model of the structure that they could use to calculate the theoretical displacements.
“This bridge is, I would say, an impressive structure,” says Daniel. “It’s made up of a steel truss supporting a concrete deck. And we’ve learned specifically that steel bridges in particular, are ideal candidates for satellite-based monitoring because their structure made of sharp elements can send strong signals back to the satellite. And it’s quite interesting in this way.”
So Daniel had the theoretical displacement data about the bridge. He then needed to compare it to the satellite data, and this is where the Brigital tool came in. Data collected by the satellite was converted into a point cloud and then fed in to the new tool, which compared the movement of the Jacques-Cartier Bridge with what was predicted and then displayed it in the 3D model format that Daniel described before.
The results were quite amazing.
Life Saving Data
Analysis showed that the bridge was moving as expected both in terms of its predicted movement due to temperature change and general local movement.“The correlation was fantastic. We could explain the expansion and the contraction of the bridge of the different parts of the bridge based on the change in the ambient temperature that was measured at the bridge or near the bridge,” says Daniel.
Knowing that bridges are safe, that they are not moving more than they are expected to, is also useful for owners of those bridges, most of which are decades old.
Having now done this for several bridges in Canada, Daniel and Cristian are confident of the accuracy of the InSAR data, meaning that they can move on to the next phase of Brigital, which is the potential we talked about right at the beginning of this episode – using the tool to create an early warning system to inform asset owners if their bridges are moving in a way that they should not.
This is the exact kind of information that has been retrospectively gathered for the UK and Italy and which could have saved lives.
The range of movement is then shown in the Brigital tool using a red, or green data display telling asset owners whether the bridges need attention. Finally Daniel and Cristian want to move on to create the kind of central database that doesn’t exist anywhere in the world right now.
Bringing Brigital to the UK
Anna Fitzgerald is the Highways Systems Manager for Oxfordshire County Council. Like the council in North Yorkshire she has a wide range of bridges to look after, some of which are hundreds of years old and she welcomes the idea of a centralised database that would give early warning on bridge movement. At the moment she says every asset owner has their own database. “I think it would be really, really useful to have that collective approach but also some predictive modelling so that you can tell where issues may occur in the future, you can have early warning signs, you can have major warning signs. Also a national database I think would help to collaborate work with other local authorities,” she says.
Better data is a big challenge for Anna and other local authorities who have been at the sharp end of local authority budget cuts. Austerity has hit councils hard over the past decade reducing the numbers of inhouse staff. Roads and bridges have to compete with health and social funding, education and services like waste collection. Meanwhile bridges are getting older. According to data from the driver RAC Foundation there are over 3000 bridges in the UK that are in such a poor condition that they are unable to carry heavy traffic. Repairing them would cost over £1bn and councils can’t afford to spend the money to do it. Instead they introduce weight limits and divert heavy traffic along other routes. Anna says that having centralised asset data would support these councils to target repairs and maintenance more effectively.
Making Infrastructure More Digital
Charlie Davies is an innovation and research engineer at contractor Costain, which describes itself as a smart infrastructure solutions provider. It maintains bridges roads and other infrastructure for clients all over the UK. He says that embracing new technologies like Brigital is not just useful, it is vital. “It is a well-known fact that productivity and efficiency within the construction sector is behind the curve for manufacturing and other leading services so we need to transform our industry to enable change that will help us to deliver major infrastructure to time and to budget as an industry as a whole, not just as Costain,”
In this context then he says that remote monitoring using tools like Brigital and other types of remote data collection is the direction that the industry needs to head towards. Charlie is also excited about the potential for this technology in other areas from buildings to network monitoring of road and railways.
Another advantage is that using satellite data means that movement is being monitored much more frequently. Some LEO satellites orbit the earth every ninety minutes. But under the current system bridges are only inspected every two years at the most. “A lot can change in two years,” says Charlie. “When you look at the rise of extreme weather and the increase in usage of our assets and our infrastructure, so an increase in the frequency of inspection is hugely valuable in having an optimally performing infrastructure.”
Spatial Planning with Satellite Data
Sam Li is a senior innovation lead at Transport for Greater Manchester and he says that his department acts as a kind of pathfinder, discovering how new technologies can help improve the city’s multitude of transport systems. “There is a huge opportunity with satellite application data for us to better understand our assets and infrastructure and the conditions they’re currently in,” says Sam. “A lot of our asset management requires people on the ground, or IoT type sensors, and they carry a significant costs where software applications, and earth data could provide that solution at a much lower cost without us constantly sending out guys on the ground to examine them”
But it isn’t just asset monitoring that Sam is exploring. He thinks that satellite data could help cities improve their spatial planning. “We know that the rise of satellite imagery and Earth observation data, people are starting to use this to help look at city planning and the growth of a city as a whole. So we’re aware that a commercial company is now starting to use satellite application imagery to determine number of cranes in the city to really understand the near the level of growth is going at. For us as Transport Authority, we want to better understand everything from people movement to air quality and satellite data could potentially help us with that as a whole.”
And this is where the Catapult hopes to support organisations like TFGM and any businesses that are interested in exploring the potential for satellite data. Its mission is to open up new markets. “Our aim is very much to make sure that these markets are opened up, that there are customers aware of the potential and to acquiring the services that are created so if anyone is at all interested then they should absolutely be coming to talk to us to understand what the power of satellites is and how they can really help them benefit as they move towards thinking about how they work in the future,” says Dr Sam Adlen, Chief Strategy Officer at Satellite Applications Catapult.
