Digital close-range photogrammetry for dimensional checking and control in a shipyard

Automatic or semi-automatic systems for digital close-range photogrammetry are a very efficient and accurate tool for a large number of measuring tasks in industrial production processes. This presentation shows experiences and results of some pilot studies on the applicability of digital photogrammetric techniques in production and quality control conducted on a north-american shipyard. The main task was the dimensional check of sections of a ship's hull manufactured and equipped in a hall and to be fitted into it's location in the complete hull under construction in order to avoid expensive refitting work during the final assembly of the hull. An off-the-shelf high-resolution stillvideo camera Kodak DCS200 was found to be very useful for data acquisition; it proved to be an autonomous, flexible digital image acquisition system with a high accuracy potential. The items to be measured were discrete points targeted with retroreflective markers. Due to the relatively small number of targets to be measured and the high complexity of the scenes semi-automatic data processing was chosen. The results of the study were quite satisfactory: it could be shown that a system largely based on standardized hardware components is well suited for the tasks, and a relative accuracy of up to 1:75,000, which can be considered a good value under factory floor conditions, could be achieved.