image and the existing maps. During this operation the congruent bundles of rays
are projected in the form of a mixed image of greenish yellow color onto the map
tracing table. Filter spectacles are not needed, generally, for map revision ef
forts. For contour plotting a special plotting table is provided and viewing is done
with conventional red and green filter spectacles. Illumination consists of two
lamps and Fresnel condenser with anaglyphic filters mounted between the lenses.
CBS LABORATORIES.
The CBS Laboratories, Stamford, Connecticut, USA, has produced several
items of interest in photogrammetry during the period 1964-68, including a
’’Superimposition Viewer” and a "Double Image Enhancement Viewer.
a. Superimposition Viewer. A unique and versatile device utilizes electro-
optical techniques to satisfy three major photogrammetric services: change de
tection, screening, and super imposition. This device will electronically rectify
any two of several photographic, radar, or infrared formats and superimpose them
on a third format to facilitate change detection, map revision, and image inter
pretation. Its characteristics are:
(1) The film inputs may be either positives or negatives of variable
widths. Images are displayed on a cathode ray tube monitor with a high resolu
tion. Electronic reversal is possible to change from positive to negative or from
negative to positive. Magnification, either optical or electronic, is possible
through a large range. Rotation of the image of 180° is possible, as well.
(2) Electronic image correction for tilts, cylindrical distortion, and
warpage is possible. Optical image correction is used for differential scale changes.
(3) A common joystick is used for X-Y positioning.
(4) Changes in planimetric detail are detected by use of a variable
rate of flicker (from one to 12 times per second) for each image being presented
on the screen.
(5) Optional capabilities include remote display, image enhancement,
and display of remote compatible inputs.
b. Double Image Enhancement Viewer. This device provides real time,
electronically sc an-gene rated color enhancement of pairs of aerial photographic
negatives. Its characteristics are:
(1) A near ultraviolet high resolution microspot scanner (using
suitable split optics) provides the necessary scanning capability. Differences in
image intensity are extracted by an enhancer electronic processor (driven by
photomultipliers); the extracted data are written onto another flying spot scanner
(having an orange overlay output) after which the data are imaged back onto the
film plane by the same optics.
(2) A special zoom stereomicroscope is used to view directly the