Detection of railway infrastructure settlement using satellite SAR interferometry

The stability of railway tracks is an operational requirement of high importance, considering the increasing traffic loads and ageing. Conventional methods for the structural monitoring of railways use in-situ measurement devices, such as GPS, leveling or the deployment of special survey trains. These methods are generally labor intensive, expensive, and can therefore only be applied on a limited scale, either in space or time. Moreover, these methods are usually only deployed at locations where structural deformation is already suspected, requiring a-priori knowledge that may not be available everywhere. Using satellite synthetic aperture radar interferometry (InSAR) techniques, we are able to complement these conventional methods to consecutively monitor the kinematic behavior (deformation) of railway infrastructure over wide scales, with millimeter precision, and detect irregular settlement. In this paper, we mainly focus on the detection of localized differential settlements using a probabilistic approach for InSAR time series post processing. We applied our approach to all railways in the Netherlands with medium resolution Radarsat-2 SAR data acquired between June 2010 and August 2015.