SUGGESTIONS FOR SECOND PHASE OF (SANITIZED) STUDY: PI PERFORMANCE AS A FUNCTION OF STEREO CONVERGENCE ANGLE

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04770A001800020006-6
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 3
• Document Creation Date: December 28, 2016
• Document Release Date: November 8, 2006
• Sequence Number: 6
• Publication Date: November 24, 1964
• Content Type: MF

Approved For Release 2006/11/09: CIA-RDP78B04770A001800020006-6
?
SECP ET
P & DS, NPIC
Development Branch,
SUBJECT: Suggestiong for Second Phase of
tudy: PI Performance
as a Function of Stereo Convergence
Angle
The following suggestions are made in connection
with the study to determine optimum stereo convergence
angle for photo interpreters:
1. The study should simulate a satellite photo-
graphic system having the following characteristics:
a. Altitude of photography -
miles
b. Focal length of camera - 60 inches
c. Ground resolution -
(2:1 contrast)
2. Since the time limit on the study will not
allow a large photographing and testing program, the
sun elevation and azimuth angles should remain relatively
fixed in the test. Sun elevation angle should be
sufficient to obtain shadows but at the same time should
not create large shadow "dead" areas. (A sun elevation
angle in the range of 60? to 80? would appear to be
satisfactory.)
C PI E ^
oordued For Rel ase 0 111 Pr 477QA0018000200Q6 6.
 Approved For Release 2006/11/09: CIA-RDP78B04770A001800020006-6
SUBJECT: Suggestions for Second Phase of
?
0
Study: PI Performance as a Function of
Stereo Convergence Angle
3. Since it is not known if obliquity angle has
an effect on optimum stereo convergence angle, it is
suggested that the study include at least two obliquity
angles. Obliquity angles close to 15? and 35? would
appear reasonable--15 being within the range recog-
nized by PIs as degirable obliquity for stereo study
of targets, and 35 being beyond the present G system's
normal stereo coverage but within the range feasible
for future systems.
p
agreed to as consultant to NPIC, to determine
this limit (s 1 ' ' t ~`r'f`~
o
of measurement falls off rapidly NPIC re
resentatives ~t
ature. From a mensuration point of view there was
believed to exist a lower limit beyond which accuracy
4. The range of full stereo angles to be covered
in the study should be determined as suggested in the
meeting held at NPIC on 20 November 1964. The upper
limit of useable stereo from a PI point of view was
believed to have been determined and to be physiologi-
cally limited to some angle close to 300. This limit
should be determined by a study of the available liter-
r o iqui y angles out to somewhere
between 30? and 60?. It is suggested that four angles
equally divided between the above lower and upper limits
be considered in this study to determine PI optimum
stereo convergence angles.
5. In view of the limited time available in which
to conduct the study, target type will have to be re-
stricted. The following suggestions are made for in-
clusion in the list of target types from which selection
will be made:
Missile production facilities--possibly
including test stands
Missile complexes under construction
Nuclear plants/complexes
Shipyards/ship repair yards
 Approved For Release 2006/11/09: CIA-RDP78B04770A001800020006-6
SUBJECT: Suggestions for Second Phase of
Study: PI Performance as a Function of
Stereo Convergence Angle
6. Photography could begin prior to determination
of upper and lower limits lstereo angles if the scheme
suggested by of OSA (indexing camera
angle Co air a gro-u-nU speed) is used. Photography
covering stereo angles out to about 360 could be ob-
tained and the final selection of frames be made later
after upper and lower limits for the study are deter-
mined. Photography taken at aircraft altitudes will
not simulate the h/h factor of satellite photography,
however, and it is not known how much, if any, this
factor would affect results. It is therefore recom-
mended that some Nought be given to the possibility
of using present coverage of U.S. installations if
sufficient coverage exists to allow stereo pairing of
frames at a few different convergence angles for more
than one obliquity. We do not know how much such
coverage exists and if it does exist, its qu .14ty. If
sufficient good quality U.S. coverage by the camera
does not exist, aircraft coverage should sta as soon
as possible and the question material adapted to try to
compensate for any h/h factor effect.
DDS&T #3219-64