-6- 
Stereomat the raster shape and size are determined continuously during the 
scanning operation by analog electronic computers, whereas in the Analytical 
Plotter, they are determined incrementally at a relatively low rate by the 
associated digital computer. 
OPERATIONAL MODES 
The operational modes are as follows: 
Manual Mode: 
In this mode the X parallax signal actuates the Z transport servo to bring 
the two plates into alignment. The space rod carriage can be moved around 
freely by the operator. 
X Profiling Mode: 
The Z transport is driven to zero the X parallax. The space rod carriage 
is driven in the X direction and stepped in the Y direction at the end of each 
trace to form a grid across the model. The tracing speed is controlled by 
the correlation signal so as to obtain an optimum speed for every terrain con 
dition. The Y position is part of a Y position servo loop which is controlled 
from a synchro coupled to a stepper motor on the control panel. The Y posi 
tion and steps in the Y direction are chosen on the control panel with a step 
selector switch. The space rod carriage is provided with a light-sensitive 
limit sensor which is activated by reflective tape. In this manner the model boun 
daries can be chosen by laying the reflective tape down on the plotting table at 
the required points. At the end of a trace, when the reflective tape is reached, 
the drive is stopped, the panel set steps are made and the carriage drive direc 
tion is reversed to trace the next line. 
Orthophoto Printing Mode: 
The X profiling mode is used to produce an orthophoto print. To perform 
this an unexposed film is inserted in the light-proof box, the printing CRT 
switched on and by tracing the entire model from one end to the other a recti 
fied image of the diapositive is built up on the film. The space rod carriage, 
and thus the orthophoto carriage speed, is controlled by the correlation signal, 
which varies continually to adapt to the terrain conditions. To avoid uneven 
exposure of the film the lens on the orthophoto carriage is provided with an 
iris control which compensates for these variations. The average tracing speed 
can be set at the control panel and is related to the time required for the random 
scan to cover the exposed area. In the B-8, which has a model and orthophoto 
scale of from 1. 4 to 2 times the diapositive scale, the average speed for satis 
factory coverage is 7 mm. per second.