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The Scientific World Journal
Volume 2012 (2012), Article ID 519146, 9 pages
Research Article

A Synchronized Multipoint Vision-Based System for Displacement Measurement of Civil Infrastructures

1Department of Civil and Environmental Engineering, Sejong University, Seoul 143-747, Republic of Korea
2Research and Engineering Division, POSCO E&C, Incheon 406-732, Republic of Korea

Received 11 June 2012; Accepted 5 August 2012

Academic Editors: D. Choudhury and Q. Q. Liang

Copyright © 2012 Hoai-Nam Ho et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This study presents an advanced multipoint vision-based system for dynamic displacement measurement of civil infrastructures. The proposed system consists of commercial camcorders, frame grabbers, low-cost PCs, and a wireless LAN access point. The images of target panels attached to a structure are captured by camcorders and streamed into the PC via frame grabbers. Then the displacements of targets are calculated using image processing techniques with premeasured calibration parameters. This system can simultaneously support two camcorders at the subsystem level for dynamic real-time displacement measurement. The data of each subsystem including system time are wirelessly transferred from the subsystem PCs to master PC and vice versa. Furthermore, synchronization process is implemented to ensure the time synchronization between the master PC and subsystem PCs. Several shaking table tests were conducted to verify the effectiveness of the proposed system, and the results showed very good agreement with those from a conventional sensor with an error of less than 2%.