Influence of storage media on the accuracy and repeatability of photogrammetric measurements using CCD cameras

A clear advantage of digital photogrammetric measurement over other, more conventional techniques in the fast sample rate of the data acquisition. CCD cameras and video systems can be used very effectively to analyze dynamic objects or cases of rapid deformation. However, long sequences of images can introduce the penalty of large volumes of digital data, which may not be able or appropriate to be processed in real time. The images are typically stored in analog form, using media such as video tape or video disk, for off line processing subsequent to the image capture. This paper investigates the degradation in accuracy and repeatability caused by the influence of the analog recording. A number of experiments using a Hitachi medium resolution CCD camera, a three dimensional test range and a self calibrating bundle adjustment are described. For cases of near real time monitoring, the ability of frame averaging to reduce the degradation caused by the analog recording is also investigated. The results of the experiments are presented in summary to provide some guidelines as to the degree of degradation which can be expected under similar circumstances.