Photogrammetria, XIX, No. i 
SOM made two different concepts of the application of these principles. In Fig. 3 we 
show a diagram of the solution in which the connection between the space rod and the 
base carriage is entirely mechanical. In the second design electrical servo transmissions 
are inserted between the cardan joints and the straight edges, in order to reduce to a 
minimum the efforts to be exerted by space rods. At the same time the introduction of 
this electrical transmission makes it possible to keep the photographs constantly in a 
horizontal plane, as in a stereocomparator and thus avoid any problems of balancing 
moving masses (while further simplifying the optical system). 
In the mechanical instrument the straight edges 6 and 7 are directly connected to 
the two primary axes of the double cardan of the space rod. Simplicity of design is 
secured by tilting the left photograph only for (p and the right for cu. For the relative 
orientation q> v co 2 , * 2 , bz and by are available. For the scanning movements in X 
and Y a double gimbal axes system has two primary axes each. In the left half the first 
primary gimbal axis used for the (^-orientation is connected with the X-lever moving 
the plateholder. The lever for the optical system, scanning in Y-direction is connected 
to the primary axis of the second gimbal system. On the right half of the instrument the 
first primary axis coinciding with the co-axis, also carries the lever 6 for the photo 
carriage corresponding with movement in Y-direction. The primary axis of the second 
gimbal system carries the lever for scanning in X-direction by movements of the optical 
system. The consequence of this is that the «-direction in the diapositive is here vertical 
and in the left photograph horizontal. 
It cannot be denied that in this instrument chance for jamming in the upper part