(9 
(8 
E HEAR MEC TUE da CDD AME Tee BS PE NER ALONE QE EN MM OB MEC RM i SE eS I En A dn D RR SEI od LE PES OA CL LH MO c MAD c MAN GM 
Bracketed values in the table represent higher vibration veloci- 
ties which did not appear typical of the smoothest survey flying. They 
do, however, represent worse conditions which can easily arise. 
Vibration frequencies listed were estimated from visual inspection 
of graphs like figures 3 to 10. They provide an approximate indication 
of troublesome frequencies. In general, where more than one frequency 
is given for a camera, the lower one is associated with the higher 
image velocities. Frequencies down to 5 Hz were encountered. 
4.1 ACCURACY 
Accuracy of the figures and of the data in table 1 is difficult to 
estimate. Measurement of the positions of the point images is limited 
chiefly by film granularity, which tends to produce random errors. 
These are reduced considerably by some averaging which occurs in the 
data processing, and by attempts to apply intelligent smoothing to the 
hand-drawn graphs. It is believed that results are meaningful to 
within 2.5 mr/s on pitch and roll, to within 5 mr/s on yaw, and to 
within 0.5 mm/s on linear image velocities. 
5. CONCLUSIONS 
Results suggest that some improvements have been made over the 
years in the vibration isolation characteristics of mounts for survey 
cameras. For example, the RC-10 mounts in the DC-3 show about half the 
angular vibration velocity of the RC-8 and RC-5A mounts in the four 
light aircraft. Unfortunately the effects of different mounts cannot 
be separated clearly from the effects of different aircraft. The RC-8 
camera in the DC-3 aircraft was in an RC-10 mount with a special adap- 
ter and the adverse effect of the mismatch is apparent. 
It is clear that there is still a need for improvement in commer- 
cial mounts. The best run of the best commercial mount shows three 
times the angular velocity of the experimental gimbal mount built 30 
years ago. Present mounts are needlessly limiting camera resolution. 
6. RECOMMENDATIONS 
Efforts should be made to further improve vibration isolation 
characteristics of camera mounts. An anti-vibration mount cannot be 
considered satisfactory as long as vibration, rather than image motion 
due to ground speed, is the limiting factor in choice of shutter speed. 
Image motion due to ground speed, in high altitude photography for 
mapping may be 1.2 to 2.2 mm/s. This suggests, as a reasonable goal, a 
mount which could consistently keep image velocities due to vibration 
Far nated 
Tee OE