h.
m. It may
as desired.
so be ad-
1 direction
ter screw.
place by a
d in incre-
of 25 mm.
marks is
netal arm,
) the base
ncil chuck
| provision
| the map
entially a
aph of the
1ed to any
rrallel mo-
movement
vas devel-
f the T-3A
1 photog-
th camera
quipment
lique pro-
upporting
table, a
he projec-
definition
| principal
)mmodate
e depth of
PHOTOGRAMMETRIC ENGINEERING 17
(96-1&
F1G. 4. Wide-Angle Multiplex Equipment.
field is from 270 to 450 mm. projection
distance. Thus, the optimum plotting
scale is approximately 2.4 times the photo
scale for 6 inch focal length photography
and approximately 1.8 times the photo
. scale for 8$ inch focal length photography.
Dichromatic projection and observation is
utilized to give the operator a three-dimen-
sional view of the terrain. The illuminant
is a 20 volt, 100 watt incandescent lamp
with condensing lens system.
The reduction printers are nominally
Fic. 5. Wide-Angle Reduction Printer.
distortion free and have fixed reduction
ratios of 0.308 +0.2 per cent for 6 inch
focal length photography and 0.219 40.3
per cent for 8$ inch photography.
The supporting frame is designed to sup-
port 9 projectors when mounted on the
cast aluminum plotting table, providing
means for bridging control.
Prior to the development of the Wide-
Angle Multiplex equipment, this was the
standard photogrammetric instrument of
the U. S. Army for compiling topographic
maps.
Wide-Angle Multiplex
The wide-angle Multiplex equipment
(Figure 4) is designed for use in compiling
topographic maps from 9 by 9 inch photo-
graphs exposed with a 6 inch focal length
metrogon lens. The standard equipment
consists of vertical projectors, a variable
ratio reduction printed, single and double
supporting frames, cast aluminum plotting
table, tracing table and accessories. The
projectors have a principal distance of
28.182 mm. and accommodate 54 by 54
mm. diapositives. The projection distance
to the plane of best definition is 360 mm.
Usable depth of field is from 270 mm. to
450 mm. projection distance. Thus the
optimum plotting scale is approximately
2.4 times the scale of 6 inch focal length
photography. A 100 watt, 20 volt incan-
descent lamp and condenser provide the
illumination in the projector. Dichro-
matic projection and observation is utilized