Small-format fly-over photography for highway bridge monitoring

Current bridge visual inspections are time-consuming, subjective, and rely heavily on personal experiences. The resulting ratings may be inconsistent. This paper discusses using remote-sensing technologies for bridge assessment, specifically, the use of high-resolution aerial imagery. The Small-Format Aerial Photography (SFAP) is a low-cost solution for bridge surface imaging. Providing top-down views, the airplanes flying at 1000 ft, can allow visualization of sub-inch (< 0.5 inch) cracks and joint openings on bridge decks or highway pavements. However, the site lighting may influence the quality of the images; surrounding tree shades and the highway wear surface reflectivity. Several examples of bridge evaluation using SFAP aerial photography are presented to demonstrate the capability of remote sensing as an effective tool for bridge construction monitoring and condition assessment. Several imaging issues are raised about analytical techniques that are necessary to ensure proper quantification of bridge problems, which include crack detection, movement determination, heavy trucking assessment, debris detection, channel width determination and environment assessment.