11 
Figure 7 
Orthophoto Attachment to B8 Stereomat 
This arrangement ensures that the cathode ray tube, and therefore 
also the TV image of the zone scanned, will follou all movements 
of the tracing stand in parallel displacement. This means that 
the TV image is not only aluays at the correct scale for making 
an orthophotograph, but is also aluays at the correct planimetric 
position. Finally, the image on the TV screen is projected onto 
sensitized material through a projection lens rigidly attached 
to the cathode ray tube. The photographic film uith emulsion doun 
is held over the image forming system by a vacuum plate at a fixed 
distance above the table. The entire apparatus is enclosed in 
a light-tight box as illustrated in Figure 7.