Scanning head and tracing device. 
Fig. 4. 
  
Procedure 
The orientation procedure is obvious 
  
  
  
  
  
5 9— T Ue ree from Fig. 5. The sequence of points and corres- 
| x, ponding orientation elements is as follows: 
| Step Point Element 
H--+——- | Z 
| 2 1 x2 
1e Ka | kK, 42 4 4 $1 
| 5 6 wy, X1 
| This loop is to be repeated until the parallaxes 
——== disappear. Point 5 is not normally used, except 
| for checking, but when a y-parallax is observed 
¢ 2 | ¢ l at this point the adjustments must be made 
manually. 
36 i 4 y 
Practical Operation 
Fig. 5. 
The operation of relative orientation 
on the automatic stereoplotting device is extremely easy. During the first orien- 
tation loop the operator must watch the amount of y-parallax and will probably 
operate the orientation elements by hand until the y-parallax is brought down to 
about 2 to 5 mm in the scale of the model. At the same time he must adjust the 
height of the scanning head to within the same limits. At this stage the device 
takes over. When the operator pushes a button on the right side of the tracing 
table he activates the connection to the servo-system and the parallax is eliminated 
in a few seconds. The operator then moves the tracing table to the next point 
where the same procedure is repeated. 
It depends upon the magnitudes of the inclinations of the photographs 
how much similar assistance is needed from the operator during subsequent 
orientation loops. Eventually, however, all the parallaxes willbe within a few 
millimeters and the automatic stereoplotting device can perform the elimination 
without human assistance. In most cases this happens during the second loop of 
the orientation procedure. After that the operator only has to move the tracing 
table around and to press the orientation button at proper locations. 
Time Required for Relative Orientation 
  
In the tests made for this report the time for complete relative orien- 
tation varied between 7 and 23 minutes. The last mentioned value was the first 
orientation made by one of the operators on the automatic stereoplotting device. 
The average time needed for a relative orientation was 13 minutes. This, how- 
ever, included a considerable amount of time lost because of the research nature 
of the work being carried out. During the orientations a number of extra obser- 
vations and measurements were performed that would not be necessary in produc- 
tion work. It is estimated that in most cases a satisfactory relative orientation 
can be reached in 5 to 10 minutes.