Project Blue Book File on Tremonton Film, Utah, 1952

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Appendix I
Calculation of Angular Velocity of Single Aerial Object:
Pass o. 2: 48 spot positions c..re plotted, representing an elapsed time interval
of 47 frames.
At 16 frames per second, this gives:
3.0 seconds elapsed time
The measure distance on the screen is 15.1 inches. Ta.is gives approximately
15.1 or 5.0 inches per second for image velocity on the screen.
~
.
Pass Ho .
44 spot nositions are plotted, for 43 frames of elapsed time. This
time is
2.7 seconds.
The distance travelled is 15.7 inches. This gives 15.t_ 5.8 inches -oer second
'°l
­
I': .
on the screen. Average of these 2 values is 5.4 inches per second; with an es­
timated prec4sion of ±15 per cent.
Conversion to Angular Velocity:
Distance from projector lens to screen= 100 inches
Focal length of projector lens= 2 inches
EnJ.areement of film on screen= 50 times
Image velocity on film=~= ,11 inches per second
Focal length of camera taking lens= 3 inches
It is adequately precise to divide the in:age velocity by the focal length
to get the angular velocity in radians per second, then to convert to degrees.
1•re ba.ve:
Angular velocity= .11 x 57.3 = 2.1 degrees per second
3
The ~recision of this value is also conservatively set at ±151 or ±0.3 degrees
per second.