(= CS and CK treated in two different A7 autographs by different 
operators) are shown on vectordiagrammes in Figs. 2 and 3. 
The mean square value of the discrepancies in x and y as well as in 
radial direction, are shown for the various models in Table 2. 
The differences between in photogrammetric way determined 
ground coordinates of 53 check-points determined in model A (model 
AK in A7 and AV in A8) have been studied. The mean square value of 
these total differences were found to be + 21 mm in x and + 17 mm 
in y. The mean square value of the discrepancies of the mean photo- 
grammetric coordinates (not compared with geodetic coordinates) are 
consequently 11 and 9 mm respectively. 
The adjustment of the photogrammetric z-coordinates has been done 
With an approximate linear graphic adjustment (no electronic computer 
programme available) based on the general trend of the z-errors. The 
preliminary mean error in the photogrammetric elevations is roughly 
+ 30 mm. A clear systematic trend, however, remains after the rough 
adjustment. This trend coincides with the known minus-area in the cen- 
ter of the model, which may be caused by residual lens or film distor- 
tion. It should be emphazised that check-points even far out in the outer 
parts of the models have been used (see Figs. 2 and 3). A normal limita- 
tion of the model and a numerical adjustment including the distortion 
effect would improve the mean square value of the discrepancies. 
Further investigation. As soon as a programme for rigorous adjust- 
ment of a stereomodel based on the residual vertical parallaxes is avail- 
able such an adjustment will be done. The height adjustment will also 
be studied. 
Conclusion, It is quite possible to take aerial photographs from a nor- 
mal speed aircraft from very low altitude under almost any weather 
conditions at any time of the year and determine coordinates of signall- 
ed points with an accuracy in x, y and z of about -- 30 mm. Plotting 
of details and contour lines for very large scale maps is possible even in 
underexposed negatives from this very low altitude if the ground sur- 
face contains such contrasts and texture that the graininess of the film 
will not cause an erroneous stereoscopic impression. In the described 
test this was the case on the lawns of the park. 
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