ESTABLISHMENT AND CALIBRATION OF THE PHOTOGRAMMETRIC SYSTEM FOR MONITORING DUDHGANGA DAM

Abstract

Close-Range Photogrammetry affords wide ranging applications in civil engineering as an efficient and con-ventional tool for precise and reliable measurements of objects. In civil langineering, periodic monitoring of large structures forms an important and necessary aspect for maintenance and preservation of structure as it enables a regular watch on the behaviour of the structure and gives advanced information of the incoming danger so as to be able to take remedial measures well in time. The object of this study was to establish and cali-brate a suitable photogrammetric system which may serve the purpose_ of subsequently monitoring the motion wand deformations Of: a masonry dam being constructed over Dudhganga river in Maharashtra state. A wild RC 5a Camera, f = 210mm, format size 18xl8cm., modified for use in terrestrial, mode, with aerial film was used for photography. The establishment of geodetic control for stations and targets has - been accomplished with an Electronic Distance Measuring instrument and a precise-theodolite of 0.1 sec. least reading. For the reduction of data pho to gr amme tr ic/ analytical pho togr amme tr is methods have bee n used. The photographs were taken from two pairs of camera stations at average distances of 170m and 480m from the dam Two geodetic stations were established well outside the influence zone, because of unfavourable foundation problems, so as to provido the control points for calibration on the face of the dam as well as for checking the stability of the camera stations. The average standard errors in the spatial coordinates obtained from the photogrammetric system range from 1.S1cin -3.~4 cm. This accuracy has been considered satisfactory within the constraints of instruments, equipments and other 'factors. It has been concluded that with additional modi-fications, as suggested, it is possible to obtain higher accuracy, to meet the requirements of the project.