Fig. 5. The base triangle which supported the cameras. Note the spirit levels for
the check of the horizontation.
In Table 2 the coordinates and elevations of the control points for the
oblique photography according to the measurements in 1957 are demon-
strated.
The control points were signalled during the photography with cir-
cular metal disks, diameter — 120 mm, which could be placed upon the
iron tubes with the aid of well fitting plugs. The center of the signals
were marked with a white circular surface, diameter — 40 mm. Then
followed a black circle ring 25 mm and finally a white ring 15 mm, see
Fig. 3.
On the ground a number of full contrast resolving power targets
were placed, Fig. 4. The purpose of these targets was primarily to regis-
ter differences in the resolving power from one camera and exposure
to another.
2.2. The camera installation
With three theodolites a point was determined in the tower, verti-
cally above the center point 0. The point in the tower was marked with
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