Differential rectification
The period 1968-72 showed considerable in-
crease in the acceptance of the orthophoto as
a useful product, and thus existing systems un-
derwent improvements and new systems were
developed. For example, a digital control unit
was introduced for the Gigas-Zeiss Orthoprojec-
tor, with operation controlled by a magnetic
tape instead of the storage plates. H. Dell Fos-
ter introduced the Orthophotoscope RSS-goo,
which produces an orthophoto negative from a
projected stereomodel. A significant develop-
ment was the Gestalt Photo Mapper (GPM),
composed of an automated, computer-control-
led, image-correlation device which produces
orthophotos electronically. The Kelsh K-320
Orthoscan showed that a double-model ortho-
photo could be produced without moving el
ther the projectors or the film bed in the z di-
rection ; instead, flexible fiber optics were em-
ployed. Finally, a system called « Automatic
Orthophoto System » was introduced by the
U.S. Geological Survey, consisting of three com-
ponents: the Profiler, which produces terrain
profiles; the Autoline (automatic line follo-
wer) which uses the analog profiles to control
the Orthophotomat ; and a single-projector ins-
trument for off-line automatic production of
orthophotographs.
Trends and predictions
1. The aim during the 1968-72 period was
not toward complete automation ; a future
trend was forecast in the direction of a hybrid
stereoplotter system predicated upon using the
best analog/analytical combination for an opti-
mum solution to a given problem.
2. Another predicted trend was toward an
image-space plotter in which stereoimage data
are selected independent of the positioning
process.
3. In addition to those two trends, improve-
ments were forecast in the UNAMACE and
Analytical Plotters as steps toward complete au-
tomation in photogrammetry.
4. More systems for digitizing directly from
stereoplotters, further improvements and inno-
vations in image correlators, and more empha-
sis on off-line orthophoto production were pro-
jected for 1972-76.
5. Digital mapping techniques were predic-
ted.
6. Production of orthophotos from panoramic
photographs and radar imagery was predicted
as a 1976 possibility.
7. Finally, it was forecast that the topogra-
phic data bank/data base would continue to be
developed and implemented, based on the as-
sumption that it is generally more desirable
and advantageous to process data not to com-
pletion, like maps, but only to a needed form
and store the data for future production as ne-
cessary.
With the 1972 status report as a background,
the following account of developments and ap-
plications in automated photogrammetric sys-
tems covers the 1972-76 period.
CONSTRUCTION OF THE REPORT
To obtain a reasonably up-to-date overview
of recent developments in the automation of
photogrammetry, we used three principal sour-
ces of information : 1. Published literature. -
2. Personal contacts with colleagues. - 3. Res
ponses to a letter sent to cognizant individuals
and organizations in various countries, reques-
ting descriptions of the state of the art in their
field of operations.
The letter stated that the subject of the re-
port would be «a general view of the use and
application of automation in photogrammetry
throughout the world, outlining the increase,
improvements, and trends noticed since the last
Congress in Ottawa in 1972». The letter fur-
ther stated that the report would concentrate
on the following items :
1. Advances in digital and nondigital (opti-
cal) image processing as applied to automated
photogrammetric operations.
2. Advances in digital and numerical photo-
grammetry which may lead to improved auto-
mated systems. In particular: a) Digital corre-
lation. b) Development of digital profiles, con-
tours, and planimetry. - c) Development of di-
gital orthophoto products. - d) Digital (and
nondigital) map-revision techniques.
As it turned out, the information collected
is heavily weighted toward developments in the
United States, partly because automation has
indeed made great strides in the United States
but also because the response from other coun-
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