GV-62 PHOTOGRAMMETRIC ENGINEERING 
compass of data recording the ap- 
proach glide slope paths, altimeter 
calibrations, air speed calibration and 
other similar types of maneuvers. 
This limitation was soon recognized 
as erroneous. Observation of helicop- 
ter phenomena demanded the record- 
ing of trajectories much steeper, 
sometimes as high as 90 degrees, and 
early Analyzers were unable to record 
these because they demanded a lat- 
eral tracking motion to actuate the 
shutter. 
This problem was solved by the 
design of a tilt head bracket which 
permitted the camera to be tilted, 
and a bracket which allows mounting 
the instrument on its side so that the 
strips on the plate are horizontal in- 
stead of vertical. Coincident with the 
development of these accessories, the 
FrG. 7. Author tracking with a Model IV A shutter was improved so that it would 
Flight Analyzer on tilting bracket. operate as accurately and rapidly in a 
tilted or horizontal position as it did 
in its normal vertical position (Figure 7). 
  
THREE DIMENSIONAL SPACE DETERMINATION BY USE OF THE 
FLIGHT ANALYZER 
Once the principles of Flight Analyzer recording are understood, the ques- 
tion arises as to what methods exist for obtaining accurate space positional data 
when the flight course is neither straight nor parallel to the Analyzer focal plane 
as oriented. Or to put it in simple terms, how can Flight Analyzers be used for 
three dimensional space trajectories? 
Fortunately there are several approaches. It will be remembered that the 
images on the recorded projection of the trajectory have known time histories 
or records, but since it is necessary to use at least two Analyzers for three-di- 
mensional recording, there is no relation whatever between the points on the 
individual records or their time history. (If desired, it is possible to "slave" one 
Analyzer to another, but that is another story.) 
Three possible methods will be examined by referring to Figures 8 and 9. In 
Fig. 8 two Analyzers are set on opposite sides of a test site and are aligned on 
each other. Midway between them a reference plane GHIJ can be imaged. The 
Analyzer trajectory records will be reproductions of the trajectory of the air- 
craft as projected from 4 and B on this plane. These will coincide in only one 
case; where the aircraft flies in this plane of symmetry. For all other courses the 
two projected trajectories will be separated vertically. For example, when the 
aircraft is at P, Analyzer A will see it at F and Analyzer B will see it at E. Now 
referring to the small view, which is an end projection of the plane of symmetry, 
it can be seen that the vertical projection of the spacing between the two 
intercept points in the plane of symmetry is sufficient to calculate its displace- 
ment from this plane and the offset scale could be shifted for Analyzer B( M) 
to the new offset (M-O) and the space position may then be determined. 
One assumption ?n the previous description—this was made for simplicity— 
-