Infrastructure monitoring using passive remote imagery

Lead Research Organisation: University of Southampton
Department Name: Faculty of Engineering & the Environment

Abstract

Large engineering structures such as railway and highway earthworks, bridges, pipelines and dams may need to be monitored for a number of reasons. These include general performance monitoring and providing a warning of incipient or actual failure (e.g. a landslip). New infrastructure construction projects, particularly large basements and tunnels in urban areas, may require extensive monitoring systems to enable the resulting ground displacements to be measured and compensated for where necessary. The cost of such monitoring, especially over large geographical areas which may be remote or inaccessible, is significant. More efficient monitoring and early warning systems have the potential to save large sums of money, and even human life. One of the most effective ways of assessing the performance of infrastructure is to measure surface variation (displacement) and relate instability or loss of performance to the rate of change of this variation. A number of technologies are currently used for surface variation measurement; these include extensometers, D-GPS systems, prism monitoring, reflectorless laser systems, photogrammetry, and interferometric linear ground based synthetic aperture radar. All of these systems have advantages and limitations. Many are expensive, some only operate over limited distances, others require installations to monitor particular locations (such as reflectors), and some will not operate in the dark or in poor weather.The use of satellite imagery offers the potential for cost-effective measurement of surface variations. Spaceborne Interferometric Synthetic Aperture Radars (InSAR) make use of orbiting satellites to image a given area. Images from successive passes of the satellite can be used to calculate ground displacements. The primary drawback with spaceborne InSAR surface change detectors is that they were developed for global, rather than local, area monitoring purposes and have a long satellite revisit time. Another potential problem is that using only one or two satellites, an area of interest could be in an electromagnetic shadow (i.e., the satellite cannot illuminate the area due to an obstacle blocking the satellite signal). This can occur especially in urban areas or hilly terrain.Recent advances have enabled the development of a subclass of InSAR using ground surface mounted receivers, the Passive Interferometric Space-Surface Bistatic Synthetic Aperture Radar (PInSS-BSAR). The PInSS-BSAR topology has a stationary receiver fixed on the ground, with the imaging antennae pointed towards the area of interest. A satellite moving relative to the surface generates an electromagnetic ranging signal illuminating the observation area. The signal is reflected by the earth's surface, and received by the radar antennae. By using two antennae, one fixed above the other, it will be possible to calculate the change in displacement in the vertical direction. PInSS-BSAR is best utilised using non-cooperative transmitters, i.e. satellites being used for other purposes. Global Navigation Satellite Systems, such as GPS and Galileo provide large numbers of non-geostationary, simultaneously operating satellites above the horizon, which illuminate a particular region at different angles. At any time, the satellites should cover the entire surface of the planet without any points in electromagnetic shadow. The range of such as system is expected to be kilometres, and its ability to monitor continuously will provide effective early warning of excessive displacements.The proposed research seeks to develop a cost-effective monitoring system using PInSS-BSAR to measure surface variations, with specific application to linear infrastructure such as roads and railways, and their associated embankment and cutting slopes. The prototype device will be verified against existing conventional surface displacement instrumentation already installed to monitor two large failing infrastructure slopes.

Publications

10 25 50
 
Description A novel passive radar device developed by project partner University of Birmingham was tested in a series of experiments to assess its range, precision and accuracy. The intended application for the device is to measure ground movements over large areas due to landslides, tunnelling, and mining. The experiments were calibrated using more conventional laser scanning approaches. Further experiments were carried out to assess the likely error in displacement results caused by seasonal changes in vegetation cover, and the method of mapping the ground surface. The error from the former could be significant, and a method of estimating the true ground surface from information about the vegetation cover was proposed.
Exploitation Route The passive radar device needs further development before it could be used as a commercial system for measuring ground movements. The research relating to the errors associated with vegetation and mapping of the ground surface have wider application and have been published as journal contributions.
Sectors Construction,Electronics,Environment,Transport

 
Description Presentation at COST Action TU1202 final conference, Paris. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The presentation given as part of the final dissemination conference for EU COST Action TU1202 on climate impacts on infrastructure slopes.
Year(s) Of Engagement Activity 2016
 
Description Slope Engineering and Geotech Asset Management Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Speaking at a two-day conference bringing together asset owners, engineers and contractors to share best practice in solving recent failures and discuss solutions for futureproofing assets. The subject was "the role of technology in managing geotechnical assets and mitigating risks on the UK rail network."
Year(s) Of Engagement Activity 2015