ses some interesting applications of its design
in such areas as stereomates and rectification of
panoramic and radar photographs. The manu-
facturer reports that the development of the
production of stereo orthophotos on GPM II
is expected to be completed in time for the
Helsinki congress.
Preliminary results of the test carried out by
the Topographical Survey Directorate indicate
that in clear terrain the contours compiled au-
tomatically by Gestalt Photo Mapper II can
meet the accuracy standards for contours com-
piled with conventional stereoplotters. Further
studies are underway to work out operational
editing of the automatic contours and to eva-
luate the economic and operational aspects of
the new system.
Density correlation on epipolar lines
Two published articles (Masry, 1974a, b) ela-
borate on a Canadian idea of correlation along
epipolar lines. The correlator consists of a ge-
neral-purpose minicomputer, a CRT graphical
terminal connected to the computer, and a sim-
ple density-measuring attachment. The corre-
lator can be adapted to an analog or an analy-
tical plotter. (With an analytical plotter, the
control computer of the plotter can be used as
well in the correlation.) Briefly, the main ad-
vantages of the correlator are :
1. It can be adapted to analog as well as to
analytical plotters.
2. It is relatively inexpensive.
3. The main components of the correlator,
the computer and the terminal, can be used in
other applications of digital processing.
At regular intervals along a scan line the den-
sities of the photos are sampled, and the two
density traces are correlated (on - or off - line)
to determine the x position along the scan line.
Simple formulas are used to determine the
coordinates of the point on the profile, provi-
ded that the base is parallel to the instrument
base.
Various applications
Several additional articles by Canadian au-
thors present interesting approaches to auto-
mated procedures in photogrammetry. One ar-
ticle (Masry and Gibbons, 1973) explains an
automatic procedure using the orthoprinter at-
tachment to an analytical plotter for rectifying
infrared imagery.
A second article discusses in general terms
the concept of hybrid stereoplotters (Dorrer,
Lander, and Toraskar, 1974). The authors en-.
courage the upgrading of available analog plot-
ters by adding on-line computers to provide hi-
gher flexibility, ability to solve new tasks, hig-
her precision gained through self-calibration,
simplification of orientation and calibration,
and potential restitution of nonconventional
photographs. One such system is an A10 inter-
faced with a NOVA 8oo minicomputer (Tsivos
and Dorrer, 1975).
Another article (Kratky, 1975) gives a com-
plete account of a close-range application in di-
gital modeling of limbs in orthopedics. Mirrors
are used for complete coverage. the model is
digitized, and three-dimensional replicas are
produced automatically from the digital model.
FEDERAL REPUBLIC OF GERMANY
Digital vinage-processing research
Digital image-processing techniques have not
yet been introduced in West German photo-
grammetric practice. Some research and tests
nave been undertaken, however, in several ins-
titutes (e.g; Deutsche Forschungs-und Ver-
sucissanstalt tür Luit - und Raumfanrt, Institut
rür Angewandte Geodasie (IFAG), and the
I'echnische Hochschule Hanover) Both IFAG
and Hanover have obtained an Optronics
P-1700 system. The research undertaken so far
has been devoted primarily to the classification
of topographic objects from multispectral data
(«rom airplanes or satellites).
Automatic stereoplotting
The present state of the art in automated
photogrammetric equipment (Schwebel, 1971)
is the combination. ot the Zeiss ECOMA 1-114
digitizing system with the PLANIMAT D-2
plotter (with or without the Itek Correlator
C-5). The recording is in constant increments
or either travel or time. Two measuring sys-
tems, D'iM-1 and DTM-2 (for digital terrain
model data), allow the digital recording of pho-
togrammetric data by point, line, or area pat
terns. Further activities include computer-assis-
ted stereocompilation equipment (Dorrer and
Schwebel, 1974). A special interface, DIREC 1,
is built by Zeiss to connect a regular stereo-
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