102 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1976 
that these consecutive particle images were recorded. A standard error of 0.5 mm was 
determined for the spatial distance between the particle images. This error is smaller than 
expected from the standard errors ofthe grid points. This can be explained by the fact that the 
smaller distances between consecutive particle images are less influenced by systematic 
errors (lens distortion, improper film flattening, etc.) than the grid points, which cover a much 
larger area. 
When considering the scale of the photographs (1:12) and the relatively short camera base 
(base/height ratio = 1:5), the results obtained for the distances between the particle images 
and the derived velocities correspond to a standard error in x-parallax of 0.008 mm, which can 
be considered to be satisfactory. No significant improvement could be expected in determin- 
ing the small distances from photographs taken with metric cameras. 
CONCLUSION 
The applications described in this paper were based on photographs taken with non-metric 
cameras because no suitable photogrammetric camera was available at the time of the experi- 
ments for the short object distances and the rapid sequence of exposures required for some of 
the projects. In addition, some ofthe work was based on photographs that had been taken for a 
different purpose before it was decided to use them in a photogrammetric evaluation. 
Use of photogrammetric cameras would have resulted in a reduction of the preparatory 
operations such as the establishment of reference grids, etc. It has, however, been dem- 
onstrated that satisfactory results can be obtained from photographs taken with non-metric 
cameras if the necessary precautions are taken. This is particularly true for photogrammetric 
determination of short distances, such as the deformation and the velocity vectors, described 
in this paper; or when photo-coordinates measurements can be referred to a well-defined grid 
in the object space. 
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