Hybrid measurement techniques used to a study of historic cast iron suspension bridge

Abstract

Traditional measurement techniques consist of discrete measurements and they are time-consuming. Moreover, information obtained by means of these methods is limited to over a dozen points located on the examined bridge. The latest measurement methods such as laser scanning and digital photogrammetry enable to obtain quasi-continuous surface of the tested bridge. It consists of many millions of points with known spatial coordinates. The tested structure is a historic suspension bridge in the town of Ozimek in Poland. Nowadays the bridge is intended for pedestrian traffic across Mala Panew river. It was built in 1827 and it is the oldest cast iron suspension bridge in continental Europe. In the analyzed case, the measurements were performed with the use of terrestrial laser scanning (a FARO Focus 3DX130) and high-resolution photogrammetry (Canon 650D camera with the lens of fixed focus of 85 mm and the GigaPano turntable). The obtained results indicate that the differences between the two methods are within a few millimeters, which should be considered satisfactory. The advantage of the presented measurement methods is minimizing time of fieldwork and obtaining a 3D model of the bridge with millimeter accuracy.