o ( 
and mast axis and terminals of wires at bracing points. Often it was necessary to reduce several 
skew -whiff crossings of wires to one system point with the help of an auxiliary device that will be 
described later, 
The identification of the points whose coordinates had to be measured was delicate because 
of the irregular three-dimensional shape of the targets. With net intersections it was possible to 
establish a convention for setting the floating mark on the higher or lower net wire for height mea- 
surement and then move the floating mark into the intersection for position determination, Measu- 
ring the boundary cable points was even more difficult due to their poor definition by irregular 
lumps of solder with diameters up to 2 mm, 
For transferring the final models into reality close-range photogrammetry was the link 
between the model and the determination of the cutting patterns. Several tasks had to be performed: 
- Photography of the measuring models, plotting contoured plans with an analogue instrument 
(WILD A8), determination of the coordinates of detail points such as tops and foundation points 
of masts and system points, 
- Photography of the cutting pattern models, measurement of the coordinates of net intersections, 
boundary cable points and system points with a stereo-comparator (ZEISS PSK). 
The methods commonly used in photogrammetric projects had to be altered to fit this 
special case of close-range photogrammetry. Some practical aspects will presented below. 
Control points 
Although the system points had been positioned according to predetermined coordinates 
they were not acceptable as control points. The mechanicalmounting could not always be precise 
enough or sometimes these points were deliberately moved, e.g. to change the geometrical shape a 
of the roof. Therefore a new system of control points independent of the coordinate system of the e 4 
model had to be provided, 
For this purpose a large rectangular control point rack of high mechanical stability into 
which the models could be placed was constructed, Black rods with a diameter of 12 mm and 
varying in length from 5 cm to 50 cm were mounted into the frame at intervals of 30 cm, thus 
covering the entire model space. The actual target was a milled cross dressed with white plastic 
putty at the top end of the rods, Initially it was planned to determine position and height of the 
targets of the control point rack by trigonometric intersection and levelling only once before pho- 
tographing the models in order to have a net of fixed points with known spatial coordinates. Due to 
constructive changes at the measuring models, however, it became impossible to place them into 
the control point rack, The control point rods were later screwed directly into the rectangular 
frame of the models, 
To have a check on the scale, independent from the control point system, a calibrated 
2 m subtense bar and two standard meters were photographed together with the model. 
Equipment for photography 
  
The cameras used were a Sinar Norma, modified in the institute's workshop, and a Ga- 
lileo Veroplast Bi-Camera, Both cameras are adapted for glass plates with a size of 13 x 18cm2. 
The modified Sinar camera was used for near vertical, the Veroplast for oblique photography only. 
The essential characteristics of both cameras will be briefly described : 
The camera back and the lens panel of the Sinar Norma are mounted on a tube and are 
kept in position by additional braces, The focussing knob has a micrometer for reading the image 
distance, A mechanical pressure plate in the camera back exerts a symmetrical pressure on the 
glass plates and brings them into contact with four fiducial marks, The objective used is WILD, 
type 60071, No, 3, 1:11 / 115 with a between-lens-shutter and radial distortion of 0. 002 mm. 
With a tilting attachment the camera can be used for horizontal and vertical photography. In both 0 ( 
positions the camera can be levelled with built-in spirit levels, The loading of the glass plates is 
done by fabric cassettes, The Veroplast is a stereo camera with a constant base and the shutters 
may be triggered simultaneously. The aerogon objectives 1:6.3 / 150 have a radial distortion of 
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