BuL 3/1964 
157 
Traveling speed of slit in y-direction: 5 min/sec. 
Width of slit in y-direction: 2 mm 
Photographic material: Agfa halftone process him B/blue 
Illumination: 6 V, 15 W incandescent projection lamp 
While the exposure slit A travels along its meandering course of strips, the scale of the projected 
image is continuously varied in accordance with the relief of the terrain by the z-motion of the car 
riage D which holds the projection system. Further functions, such as the control of the positive-lens 
carriage in the auxiliary system, the coordination between illumination and pupil of projection lens, 
as well as the position of pivots and principal points determining optical independence, follow 
known conditions. 
Fig. 3 Meandering course of the exposure 
slit during orthophotoscopie rectification. 
Instrument 
GZ1 
Fig. 4 Operation of Orthoprojector by 
"direct method”. 
At the present time, there are two different possiblities of driving the Orthoprojector, which are 
illustrated in the block diagrams: 
In the first method (Fig. 4), GZ 1 and plotting instrument are connected mechanically or through 
selsyn systems in x, y and z. The plotter operator controls only the z-motion by keeping the floating 
mark in contact with the surface of the terrain model, which incidentally has been oriented in the 
normal manner. Any instrument may be used as a plotter, provided that it is sufficiently accurate 
and that it is driven in x, y and z by spindles. The projector tilts d and a> as well as the other initial 
values (x , y o , z Q ) are determined in the plotting instrument and set on the GZ 1. 
4. Storage techniques 
In the second method (Fig. 5), the operator records the values determined in the plotting instru 
ment in a store S. This storage is effected in the form of scribing. Temporally independent, these