• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.125-133
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• 1989

For convergent photos, which are now widely adopted for terrestrial facility survey, a number of experimental studies and theoretical studies on the developments of accuracy predictional model according to the convergent angle change have been accomplished. And such studies are basically depend on the symmetrical geometric configuration at the normal direction to the center of the object. However, in may cases of facility survey such as building facades, bridges, dam surfaces, relatively flat topography, etc., the object features are almost like planar, and frequently the surroundings do not allow the photo station at normal direction, and the sufficient convergent angle can be hardly achieved. Considering those points, in this study, the accuracy analysis on three dimensional coordinates according to the variations of photo direction and of convergent angle to the planar object were attempted, and the optimum geometric configurations at the normal, side-looking, and the most side-looking direction were investigated. The result through this study show that from normal direction to the side-looking direction angle ${\tau}=30^{\circ}$, the larger the convergent angle, the higher the accuracy, and in case that right photo is at the most side-looking direction, the better accuracy can be achieved according to the convergent angle increase up to $60^{\circ}$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.541-547
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• 2017

Climate change has become the main cause of the exacerbation in natural disasters. Social Overhead Capital(SOC) structure needs to be checked for displacement and crack periodically to prevent damage and the collapse caused by natural disaster and ensure the safety. For efficient structure maintenance, the optical image technology is applied to the Structure Health Monitoring(SHM). However, optical image is sensitive to environmental factors. So it is necessary to verify its validity. In this paper, the accuracy of estimating the vertical displacement was verified with respect to environmental condition such as natural light, measurement distance, and the number of image sheets. The result of experiments showed that the effect of natural light on accuracy of estimating vertical displacement was the greatest of all. The measurement angle which was affected by the change in measurement distance was also important to check the vertical displacement. These findings will be taken into account by applying appropriate environmental condition to minimize errors when the bridge was measured by camera. It will also enable the application of optical images to the SHM.