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it will lead to the unification which is a most 
desirable feature and also it will lead to simpli- 
  
SERVO > 
AMP 
  
  
  
\ ‘Y'PARALLAX 
  
  
AUTOMATIC STEREO 
O O SWITCHES 
Q (92) ORIENTATION 
MOTORS 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
SIGNAL 
a RIGHT IMAGE SIGNAL P 
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CIRCUITRY LEFT IMAGE SIGNAL 
i T.S.M. TRACING 'X' PARALLAX PHOTO 
^ SIGNAL VELOCITY SIGNAL CELLS 
SIGNAL \ 
i m \ / PHOTOGRAPHIC 
X BER S REF VELOCITY ( * V 7 TRANSPARENCIES 
CONTROL \ / 
<> CD LENSES 
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'Z' MOTOR x * 
SCANNING \ / 
4 GENERATOR l SERVO \ 
AMP | / 
à 
CATHODE 
, , RAY TUBE 
x DEFLECTION SIGNAL 
+ > > DEFLECTION 
< > — > COIL ASSEMBLY 
Y'DEFLECTION SIGNAL 
'X' OR' Y' MOTOR 
  
  
SERVO 
  
AMP 
  
  
  
Figure 4. System Block Diagram Normal Mode 
the motor. The operator repeats this procedure 
at each of the parallaxing stations in order, 
selecting the appropriate motor in each case. 
The X parallax signal operates the Z servo 
motor during relative orientation thus removing 
X parallax by a vertical motion of the C.R.T. 
The Z motor maintains the pattern centre in 
contact with the model surface, as the operator 
moves the C.R.T. carriage horizontally in the 
model area. The pattern centre, during automatic 
operation, is the equivalent of the floating mark 
during manual operation. X parallax is removed 
by a vertical motion of the C.R.T. also during 
*absolute orientation" and during the plotting of 
planimetry. The operator is thereby relieved of 
the necessity of keeping the floating mark on the 
ground. 
Topographic Plotting 
Stereomat plots topography automatically, 
either by profiling or by contouring. Image and 
terrain conditions automatically control the speed 
at which the profiles or contours are traced. 
Contouring is the traditional method of 
plotting topography, and offers the great ad- 
vantage of a two-dimensional presentation that 
is directly related to the planimetry. Unfortu- 
nately, fully automatic contouring of an entire 
model is difficult. Stereomat automatically 
traces out individual contour lines rapidly but 
additional means are required to ensure that none 
of the contours has been missed. Contouring 
is fundamentally a more complex operation than 
profiling, and involves additional circuitry for 
steering the floating mark. 
Profiling automatically covers the entire 
model, but is wasteful of time since much of 
the profile data is redundant in the flatter areas. 
The chief objection to profiling as a topographic 
plotting method however, is the difficulty of 
storing and presenting the profile data and of 
relating it to the planimetry. 
Automatic profiling is useful for 
area and volume measurements, since the data 
is not used directly but is processed by a com- 
puter to yield the required answers in numerical 
form. 
Contouring and profiling speed is controlled 
by a tracing-velocity signal derived from the two 
image signals by means of a multiplying corre- 
lator. Tracing velocity is thereby dependent on 
the degree of image correlation at any instant, 
and any factor that reduces image correlation 
reduces tracing velocity. 
Parallax reduces correlation. If the servos 
are unable to clear X parallax during rapid pro- 
file or contour tracing because of dynamic limi- 
tations, the reduced correlation will decrease 
TUUOITU, UTUACT. CTIUU TTLATUSTULU OJ IVIF I1CIUVG, Durmno 
adequate record of the discussion is available 
for publication. 
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