4 
With such high contrast imagery, image motion-compensating 
devices become less important because the reduction of the 
image center location can be executed reliably by geometric 
considerations, in context with shutter performance data, lens 
transfer functions and emulsion-response characteristics. 
Therefore, it appears that neither the principal photo- 
grammetric sensor, the lens, nor the recording techniques 
(the photographic medium) are the sources of primary concern. 
The real problem seems to lie in the environmental con 
ditions of the camera itself. This environment is not only 
quite different from the conditions under which the sensor 
was calibrated, but close inspection shows that these con 
ditions are, in general, actually incompatible with the require 
ments for precision measurements. Accomplishments in environ 
mental control for remote sensing in space missions suggest 
that techniques have been developed which are applicable to 
the problem at hand by either providing adequate environmental 
control for the camera system, or suggesting the monitoring 
of critical parameters of the environmental conditions in 
order to introduce corresponding corrections during the data 
reduction process. 
A considerable gap of knowledge seems to exist, however, 
with respect to the influence of air turbulence or, in other 
words, of the pressure gradients under the airplane in front 
of the camera lens or viewing window. Typically, a lack of 
concern is tolerated concerning the optimum location of the 
photogrammetric camera within a particular airplane con 
figuration, as indicated by the selection of the mounting 
area mainly in accordance with structural considerations or 
because of convenient operating conditions. 
Later, evidence will be given regarding one such atmos 
pheric disturbance, the influence of scintillation, on the 
geometric positions of satellite and star images. These 
results raise a question about the limitations on geometric 
fidelity in individual aerial photographs which, although taken 
under reduced absolute pressure levels, are nevertheless 
typically acquired with small apertures and short exposure 
intervals. Both conditions enhance the undesirable effect 
of air turbulence on metric photography. 
These general remarks have been presented only to con 
vey an awareness of problem areas which must be dealt with, 
one way or another, in attempting to use the photogrammetric 
method as a tool to determine highly accurate directions to 
specific target points. Such directions are the essential 
information in all spatial triangulation.