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tive material (plates and film), filters etc. interesting information can 
be obtained on the specific influence of those factors upon the geomet- 
ric quality of the negative. 
2.1 The control points and the geodetic measurements 
The arrangement of the control points is demonstrated in Fig. 2. 
There are two different systems, one for vertical photography (the thin 
circles and the center point, the triangle denoted 0) and another for 
oblique photography (the thick circles and the center point, the double 
circle denoted KO). The notations of the points for oblique photography 
all contain a K. The latter points were geodetically measured in 1957. 
All points were marked with iron tubes about 1.5 meters in length 
and about 0.025 meters in diameter. All points were protected with iron 
or wooden covers. 
The accuracy requirements concerning the coordinates of the control 
points are rather high. For aerial cameras c — 150 mm the image scale 
becomes about 1:800 which means that 1 micron in the negative corres- 
ponds to about 1 mm on the ground. For a high precision investigation 
of the camera it is consequently desired that the standard errors of the 
geodetic coordinates are not larger than about 2—3 mm, 
The geodetic measurements were first concentrated to a first order 
network consisting of the basic points 0, 108, 208, 308, and 408, see Fig. 
2. The angles in this triangle net were measured with high precision and 
the distances from the center point (0) to the four points were measu- 
red with a well calibrated invar measuring tape (96 meters). 
The distance measurements were repeated several times and gave 
good results. The triangle net was adjusted according to usual principles 
(the method of least squares). The standard error of the directions 
became 07,0007 (centesimal grades) after the adjustment. 
All other points were determined with simultaneous intersection from 
three of the basic points in suitable combinations. The discrepancies of 
the redundant directions were adjusted according to the method by 
Werkmeister. The final point was determined as the point of gravity of 
the three corners of the error triangles. Directly from the magnitude 
of the error triangles an estimation of the accuracy of the coordinate 
determination could be done. The standard error of the intersected 
points was found to be of the magnitude 2—3 mm, which is satisfactory 
according to the statement above. The elevations of the control points 
were determined by precise levelling. From repeated, independent series 
of measurements the standard error of the final elevations was estimat- 
ed to 1—2 mm. 
With the aid of a series of trigonometric measurements the elevation 
of a certain point in the tower near the position of the camera was de- 
termined. From the adjustment, the standard error of the final eleva- 
tion was estimated to about 10 mm. 
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