Optical EngineeringDesign of an expert measurement system for close-range photogrammetric applications
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Digital photogrammetric systems have been used to solve various measurement problems in industrial applications for many years. Industrial line-scan video cameras have been widely used in these systems and in machine vision applications. This paper addresses the use of a digital photogrammetric expert measurement system for deformation measurements on the surface of concrete materials. The system consists of two industrial cameras having fixed-focus lenses. Because the accuracy of the photogrammetrically derived object data mostly depends on the camera calibration, the system had to be calibrated first. A 3-D wooden object was specially designed and constructed for that purpose. A measurement process of 17 steps was carried out to determine the displacements on the surface of the samples. Linear variable differential transducers were also used to measure the deformations in a conventional way. Data obtained from the two sets of measurements confirmed the system's reliability and allowed us to monitor surface behavior of the concrete samples under loading.