Engineering aspects of photogrammetric plate measurements, including the development of a novel interferometer
Two different factors involved in the measurement of photogrammetric plates have been studied. A novel interferometer designed to monitor the position of a microscope stage, to be used to measure photogrammetric plates, has been built. The prototype instrument is able to give the position of the stage with a maximum error of less than 200nm. An algorithm has been developed for a motor driven x-y microscope that is able to search a photographic plate automatically for targets, and record their positions. In a trial survey this system was able to measure the positions of the targets on the plates with an uncertainty of approximately 2gm. This result is comparable with the precision that a human operator could achieve using the same equipment, but without the fatigue effect associated with visual observation. Virtually no human interaction is necessary for the system to function.