Measuring Bridge Deflection with Aerial Drone Photography

Abstract

Aging social infrastructures necessitate increasing maintenance and management efforts. Accurate deflection measurement is essential for evaluating bridge integrity. The sampling moiré method, using digital cameras to capture grating patterns on structures, typically requires a rigidly fixed camera. However, locating suitable fixed points for photographing bridges overseas or mountains is often impractical. Recently, drone-mounted cameras have emerged as a promising inspection technology for bridges and transportation infrastructure. This study introduces a novel displacement measurement method with drone aerial photography and moiré phase analysis. Laboratory tests on a 50-mm-pitch grid pattern demonstrated its effectiveness, alleviating the need for fixed cameras and enabling deflection measurement in diverse real-world scenarios.