ABSTRACT
This paper presents the major specifics of space-borne synthetic aperture radar (SAR) interferometry (InSAR) techniques to be addressed for monitoring deformations of typical concrete or metallic bridge structures. The possibility of monitoring subtle displacements of bridges from space is possible since modern high resolution satellite SAR data. Thus there is only a limited number of research works related to bridge monitoring using InSAR currently (Fornaro et al. 2013, Monserrat et al. 2011). In this work we describe possibilities and give some additional value in providing basic possibilities of mathematical analysis of the accuracy and sensitivity of the radar phase with regards to bridge displacements, partially based on previous research (Lazecky et al. 2015a, b, Sousa et al. 2015).
Three case studies demonstrate the applicability of very high resolution TerraSAR-X satellite data for continuous monitoring and a potential for an early detection of dangerous deformations from the time series of SAR measurements, eventually. These studies are related to problematic subsiding bridges of D1 highway in Ostrava and Radotin bridge system in Prague, Czech Republic and to Stary most bridge in Bratislava, Slovakia.
In all three cases, the displacements due to thermal dilation is clearly observable from the time series of SAR phase measurements and partially distinguishable from the mixture of all the phase factors, that includes also linear deformation trend in vertical and horizontal directions and stereoscopic effect of height difference of observed objects. It is expected that with a longer time series, at least a year and half of data is needed, in order to avoid potential temporal trend of temperature data (Lazecky et al. 2015b). Figure 1 demonstrates result from Persistent Scatterers (PS) InSAR technique applied to a set of 15 TerraSAR-X stripmap images over damaged Ostrava bridge ranging 10/2013-02/2015. Linear deformation trend of Ostrava-Trebovice highway bridges estimated by TerraSAR-X PS InSAR processing. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig38_1.jpg"/>
