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——— UO 1 
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which cannot exceed a certain magnitude. A complete compensation of the 
orientation errors occurs only in the vertical section through the right camera 
station. In the other cylinder sections, y-parallaxes which are small values of 
the second order will be present, if the orientation errors are small values of 
the first order. The condition that this parallax may not exceed the limit, set 
by the possibility of observation in the plotting instrument, permits to estimate 
possible maximum of orientation errors. Under normal photographic condi- 
tions, the results of this estimation in precision plotting instruments will be: 
Standard-angle views Wide-angle views 
do" = 45,3’ domes = 34,4 
db," = 4.0mm db," = 3.0mm 
db,"* — 1.0 mm db,"* — 0.8mm 
and for 2nd-order instruments 
Standard-angle views Wide-angle views 
damax = 82.6' dao z 62,7 
db > = 7.2mm db,""* — 5.5 mm 
db,"* — 1.8 mm dbx = 1.6mm 
The corresponding maximum elevation errors which may occur in the 
model, are as follows: 
For first-order plotting instruments 
Standard-angle views Wide-angle views 
0.57% of the flying height 0.50% of the flying height 
For 2nd-order plotting instruments 
1.04% of the flying height 0.90% of the flying height 
In the critical photographic case and at a flight altitude of 4,000 m, there 
may be elevation errors of about 20 m for precision instruments and of about 
40 m for second-order instruments. These values show that the correction of 
relative orientation by additional observed elevation control errors is actually 
possible. 
Under the angle of the overall problem of double-point projection in space 
the critical surfaces will therefore not produce an uncertainty of orientation. 
Errors of relative orientation which are caused by critical surfaces may always 
be eliminated within the scope of absolute orientation.