Satellite Monitoring of Transportation Infrastructure

Abstract

Harsh weather conditions caused by climate change and increased traffic loads can accelerate the aging process of core public infrastructure. Conventional condition assessment methods primarily rely on visual inspections conducted years apart, making it difficult to detect subtle, ongoing changes in performance resulting from structural deterioration. Consequently, engineers may be unable to initiate early countermeasures to prevent service disruption or structural failure. In response, public infrastructure owners are actively seeking innovative solutions that can help maintain high levels of user safety, reduce service disruption, extend the service life of infrastructure, and lower overall life-cycle costs. To this end, the National Research Council Canada, Transport Canada, and Infrastructure Canada have collaborated for several years to adapt, further develop and validate space-based earth observation technology for monitoring key public infrastructure, including bridges and, more recently, marine ports and airports. Case studies on runways of the Vancouver International Airport and wharves of the Vancouver Fraser Port have been conducted to validate remote satellite observations with in-situ surveying subsidence measurements. Satellite image interferometry allows the mapping of displacement by determining the signal phase change within pairs of co-registered pixels from two radar images of the same target taken at different times. The result is a line-of-sight (LOS) displacement measurement that can be used to remotely assess uplift, subsidence, and horizontal motion taking place over time. Since it is a 1D measurement taken at an angle from the zenith, the vertical and horizontal components are unknown a priory. Thus, attempting to validate satellite LOS measurements with in-situ surveying vertical measurements can be challenging since one has to make valid assumptions about the horizontal movements of the ground targets being measured – in our case, the riding surface of the airport runways or the port wharves. This paper compares satellitemeasured displacements and field survey measurements at selected locations and discusses challenges associated with the interpretation of satellite measurements.