A robust line-tracking photogrammetry method for uplift measurements of railway catenary systems in noisy backgrounds

For electrical railways, contact wires are used to ensure stable and continuous power supply to trains operating on the infrastructure. One crucial design parameter used to control the catenary design is the vertical displacement. The traditional uplift measuring equipment of catenary systems usually requires that targets are installed on the wire, and/or that measurement devices are mounted on the support structure of catenary systems or temporary poles. These methods require track access and substantial time and manpower for installation and measurement. Thus, a portable vision-based tracking system is proposed to enable remote, non-contact and non-target uplift measurements of catenary systems. The challenge in measuring the catenary displacement is to detect a linear rigid body in a noisy background environment with a high sampling frequency. To detect the displacement, a vision-based system with a novel line-tracking technique is used to achieve robust and accurate measurement. The proposed technique is based on a coarse subset and line search and subpixel detection. The line-tracking method is successfully employed for the identification of the important vertical displacements of a contact wire in front of a noisy background. The accuracy, robustness and applicability of the proposed tracking method are demonstrated through numerical experiments, the field uplift measurement of the railway catenary system and the identification of the contact wire in a diverse city environment. (C) 2020 The Author(s). Published by Elsevier Ltd.