A tentative test for measuring the sub-millimeter settlement and uplift of a high-speed railway bridge using COSMO-SkyMed images

Abstract

This paper analyzed the dynamic behaviors of a high-speed railway (HSR) bridge and evaluated the possibility of measuring the sub-millimeter settlement and uplift using COSMO-SkyMed images. The capability of synthetic aperture radar interferometry (InSAR) technologies with the purpose of sub-millimeter deformation monitoring without ground control points has rarely been studied. In this paper, we conducted a tentative test for measuring the sub-millimeter settlement and uplift of a HSR bridge. Persistent scatterer (PS) and distributed scatterer (DS) were jointly detected to increase the point density. The temperature model was introduced to separate the thermal expansion and linear deformation. By analyzing the HSR structure and time-series deformation, we infer that PS points correspond to double-bounce scatterers mainly generated by the interactions between the girder and track slab and between the girder and fender, and DS points correspond to single-bounce scatterers generated by the bridge girder surface. The accuracy of linear deformation velocity and time-series deformation were evaluated, respectively. Under the assumptions by qualitative analysis, the results demonstrate that COSMO-SkyMed is capable of achieving sub-millimeter accuracy in linear deformation velocity. However, the leveling validation implies that it is difficult to achieve sub-millimeter accuracy in time-series deformation because of the uncertainties from incorrect ground data, location and time difference between the InSAR and ground data, the presence of lateral deformation, improper removal of the atmospheric phase screen, and inconsistency between the air temperature and bridge temperature.