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Centre for Digital Built Britain

 
Corner reflectors in the workshop, Krisztina for scale

Using radar monitoring is well established for investigating large earth movements and monitoring of city scale deformation, but there is limited understanding about the use of radar to monitor single infrastructure assets – which is becoming more applicable with improvements to the achievable resolution. 

This project builds on recent research highlighting the potential for satellite technology techniques to pick up precursors to failure as well as understanding the accuracy and uncertainty of measurements with respect to more widely used sensors, surveying and other methods traditionally employed to study structural behaviour. Researchers are developing methods to incorporate insights from satellite monitoring into digital information models used by built environment asset owners to improve the whole life performance and quality of assets through more effective monitoring and operational maintenance based on the data provided.

Big Picture

Deterioration and failure of critical infrastructure, such as bridges, dams and tunnels, can lead to costly repairs, disruption to transport networks and, at worst, loss of life. The catastrophic failure of the Polcevera Viaduct in Genoa, known as the Morandi Bridge, which collapsed in 2018, resulted in 43 deaths and left 600 people homeless. Closer to home, reports of the closure of Hammersmith Bridge in West London state the bridge may remain closed for six and a half years and work required to stabilise and strengthen the structure could incur costs in excess of £125 million. Only by better understanding the condition and structural health of our assets and the effects of the environment around them can we schedule effective maintenance and make informed operational decisions. Robust and reliable data can leverage whole life value of an asset or portfolio of assets by informing more efficient asset management.

The Project

InSAR (Interferometric Synthetic Aperture Radar) imagery maps ground deformation using radar images of the Earth’s surface collected from orbiting satellites and can be used to monitor millimetre-scale movements of built environment assets over time. This technique can capture measurements on a regular basis to provide continuous monitoring; radar images and measurements taken of the same area or asset collected at different times can be compared to look for changes in movement.

Researchers are exploring the capabilities of satellite monitoring to evaluate and demonstrate the potential use and value of this technique to construction and infrastructure owners and operators. The team is establishing the surveillance requirements of different assets (based on geography and material) to develop methodologies for a range of asset types and geographic locations, from bridges and tunnels in central London to road/rail embankments in the Midlands for schemes such as High Speed 2 (HS2). 

Employing data at different spatial and temporal resolutions, this project will study the quality of InSAR measurement data to better understand its suitability for use in structural monitoring. By combining structural modelling and understanding with InSAR, the team will be able to consider effects such as thermal expansion to identify unusual or anomalous behaviour in structures and explore how to better understand changes over time as a precursor to problems. In addition, this project will investigate the possibility of augmenting structures with metal reflectors used to create satellite monitoring points to amplify response enabling use of freely available satellite data from the European Space Agency. Using big data analysis including machine and deep learning to automatically extract specific insights from satellite monitoring is also being explored. 


Corner reflectors on the field near Tadcaster

Innovative processes and key insights

The project will take advantage of the large-scale archives of satellite data at different time and spatial resolutions: from data that are constantly collected every six days and freely available within the framework of the Copernicus initiative sponsored by the European Space Agency (through the Sentinel constellation of satellites), to commercial satellites such as TerraSAR-X and CosmoSkyMed-X which can be tasked to take much higher resolution imagery. High performance computing platforms may be employed to test and implement efficient scalable processing and will build on systems and knowledge already available.

Working with industry partners, the project seeks to identify where satellite monitoring is useful compared to traditional surveying techniques, establish measurement possibilities and uncertainties, improve accuracies and make use of automated learning techniques to increase the power of these types of monitoring solutions.

Developing automatic mechanisms of evaluation will be key to assessing large areas at scale. Machine learning and deep learning technologies provide a solution for automating these tasks; they are able to learn complex features and model non-linear behaviours such as those seen in complex structures. Once trained, they provide a powerful tool for automating the process of structural health monitoring and assessment. 


Map of estimated average velocity from 6 March 2015 to 6 Sep 2020 using InSAR technique with Sentinel-1 images (SatSense), showing signal of deformation for northern line extension from Kennington to Battersea station and for dewatering works associated with Thames Tideway.

Challenges

Infrastructure and built assets in remote and hard to access locations make monitoring challenging, high risk and costly. Satellite monitoring can provide regular data to help to build a fuller picture of the structural health and behaviour of an asset. Satellite monitoring does not require a power source, covers the entire earth and radar can image continuously through clouds day and night.

Timeline

The research team have been working on designing and testing a new array of corner reflectors suitable for infrastructure monitoring. These reflectors aim to enhance existing and freely available Sentinel-1 InSAR measurements. These are smaller than traditional reflectors and researchers will test whether several small reflectors can be used rather than the larger metre-scale corner reflectors which are traditionally used for ground motion measurement but not suited for deployment on structures such as bridges. The design, manufacturing, and deployment of these reflectors have been completed and researchers are currently collecting InSAR and Global Navigation Satellite System (GNSS) data in order to test how well they work.

To better understand and predict reflectivity of a bridge in satellite SAR images prior to construction, researchers simulated SAR reflectivity maps of three bridges with different scattering characteristics in London at X band and compared them with the real TerraSAR-X images. The team also linked the strong point signatures in the simulated images, which can be selected as coherent pixels by InSAR, to 3D scattering centres in 3D models of the bridges. This allows researchers to find which surfaces of a bridge interact with radar signal to generate signals seen in the InSAR data.  The team are working on improving InSAR performance by modification of the standard approaches and on validating InSAR results using existing ground-based measurements for some challenging case studies.

Each satellite measures in line-of-site (1-d measurements) and researchers are combining the different satellite directions to study how well 3D motion is captured. The team is now working on the comparison of results (scatterers) between different datasets across a variety of bridges with a view to characterising the reflections from bridges with data at a range of resolutions. The use of different techniques for different bridge types (there are 10-15 bridges in central London with different structural and material characteristics) will also be explored. The multiple satellite directions will be used to better understand the potential for InSAR decomposition of 3D movements by comparing these movements to a structural model calibrated to the bridge using the collected measurement data (pre-tunnelling events) as well as temperature and tide data,

Industry Impact of research

The project will build on established interaction with asset owners who are in partnership with researchers for this project by capturing user requirements and obtaining feedback on designs and implementations. This approach secures value for industry by steering outcomes of the project towards deliverables that can be used in practice by asset owners. The project explores satellite remote sensing, in particular InSAR measurements, to be used in addition to existing ground-based measurements in infrastructure monitoring. It allows large-scale nation-wide monitoring of structural health of bridges, rail networks and other infrastructure, and could be key in forecasting potential failures or collapses.

“Satellite derived data can mitigate the risk of failure and provide significant cost savings as it facilitates non-intrusive structural health assessments of different types of assets. This approach provides significant value to industry by reducing human effort, minimising construction and O&M costs as well as providing useful structural health information to ensure rapid and effective operational decision making.”

Tariq Darwood, R&D Expert, EDF R&D UK Centre

Wider benefits

Combining a range of monitoring technologies enables assessment of new generation techniques such as satellite monitoring and comparison with more traditional monitoring. Satellite radar imagery to monitor structures is becoming more accessible and available at increasing spatial and time resolutions and its capability to monitor over large areas and in remote locations could provide valuable insights to asset owners and managers.

With the effects of climate change around the world resulting in extreme weather events, such as flooding, the use of satellite monitoring can track changes in a geographical area as well as individual structures providing potentially important indicators of change. InSAR imagery could be combined with other satellite data sets (optical, hyperspectral) to monitor changes in vegetation, environment and land use.

Case studies from this project will support industry to better understand satellite monitoring technology in the context of infrastructure and construction. Bespoke trials are costly exercises for suppliers who are often small SMEs with limited financial means and this project will provide assessment of the technology.

Meet the research team

Lead: Professor Campbell Middleton, Laing O’Rourke Centre for Construction Engineering and Technology, University of Cambridge; Professor Tim Wright, Professor of Satellite Geodesy, University of Leeds; Dr Sakthy Selvakumaran, University of Cambridge

Team: Dr Gabriel Martin Hernandez, Senior Research Associate, Laing O’Rourke Centre for Construction Engineering and Technology, University of Cambridge; Dr Zahra Sadeghi and Dr Krisztina Kelevitz, Research Associates, University of Leeds; Professor Andy Hooper, Professor of Geodesy and Geophysics, University of Leeds

 “This research in academia has immediate applicability to society by expanding InSAR remote sensing applications into infrastructure monitoring.”

Dr Krisztina Kelevitz

 

 

 

 

 

“Many bridges are only inspected visually every few years. We are excited by this technology as it can potentially provide real monitoring data for all bridges and can possibly provide an early warning of any structural issues.”

Dr Zahra Sadeghi

 

 

 

 

“The use of machine learning technologies on the evaluation of the data obtained from assets will allow us to monitor and assess these structures at large scale in an automatic fashion. As satellite images collect data from large areas continuously, it would not be cost effective for experts to evaluate this data manually and at scale.”

Dr. Gabriel Martin Hernandez

Engage

If you would like to know more about this project please contact Dr Sakthy Selvakumaran or Professor Cam Middleton.

To follow progress with this project visit the project page here.

Need to know

  • A satellite 600 km above the earth can measure relative ground movements of less than 1cm  
  • The Sentinel-1 radar constellation acquires four images every six days for most of the UK
  • InSAR can see movement due to landslides, sinkholes, subsurface tunnelling, resource extraction and even track the build-up of volcanic eruptions