A TEST OF CLOSE-RANGE PHOTOGRAMMETRY

Care was taken to generate high-contrast targets for calibration and measurements. These target coordinates were documented with an order of magnitude more accuracy than achievable using photogrammetry. The repeatability of the film measurements was also an order of magnitude more accurate than photogrammetric coordinate determinations.
The best accuracy for in-plane measurements of X or V was approximately 0.2 percent (1 part in 500) and 0.4 percent (1 part in 250) for range Z measurements.
It is not obvious how the accuracy can be easily increased using this hardware; measurements for the purpose of quality control of typical parts manufactured by machining and grinding is out of the question.
Measurements for quality control of bent sheet metal may be possible. Certainly automobile accident reconstruction scenes, general archiving, and similarly relaxed environments have applications for this accuracy.
This fine-grain film with its 35-mm format has an order of magnitude more resolution than a typical solid state CCD imager. Furthermore, it is difficult to perceive object targets which result from features of the part itself that would even approach the contrast of the special targets used here.
More accuracy is, however, obtainable from convergent cameras, redundant cameras, calibrated optics/principal points, large-film format, stereo-plotter measurements, and error minimization techniques.