Image-based Deflection Measurement and Error Analysis

Abstract

Abstract This paper gives an image-based and computerized solution to the deflection measurement of bridges with its corresponding design scheme of measuring devices. A laser transmitter is fixed on one end of the bridge. A dark cartridge with an optical screen and a camera is installed in the middle of the bridge. Light beam projects onto the optical screen, while the camera captures the image on the screen. Bridge deflection is measured by applying image-processing algorithms and then performing the related computation. The systematic error caused by tilting film and geometric distortion is analysed and eliminated. One of the advantages is that, this low-cost measuring scheme obtains direct deflection data and requires simple operations comparing with existing methods. Other advantages and disadvantages are also highlighted.