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NON-TOPOGRAPHIC PHOTOGRAMMETRY, 1972-1976 43 
ments of particular interest to Commission V 
were introduced since the Ottawa Congress in 
1972. 
Zeiss G2 Stereocord. This isasimple plotter 
for computer-supported plotting. It is based 
on the design of the Zeiss Stereotop and is 
intended for those areas of application where 
the high efficiency of precision stereoplotters 
is not warranted. The analog-mechanical 
computers ofthe Stereotop are replaced by an 
electronic desk calculator (or a minicomputer 
ifthe user so desires). The new plotter can be 
used to plot from aerial, terrestrial, and ob- 
lique stereograms. Furthermore, it can be 
used to plot from single photographs, espe- 
cially when a perspective grid is superim- 
posed in the picture. In addition to the digital 
readout of object-space spatial coordinates, it 
is possible to undertake direct on-line compu- 
tations of such parameters as distances, differ- 
ences in elevation, slopes, direction angles, 
areas, and volumes, and to perform statistical 
evaluation of these parameters. 
The Micro Surfer (also known as EMPD)of 
Cartographic Engineering Ltd., England. 
This instrument has been specifically de- 
signed for the three-dimensional analysis of 
scanning photo-micrographs. Stereo pairs of 
micrographs taken at a known tilt angle, nor- 
mally 10?, are inserted in the instrument 
which can acceptany size micrographs up to 4 
in. X 5 in. It is designed for either contact 
prints or transparencies. These are observed 
with stereo optics at 2X magnification. A bal- 
anced lever attachment moves the photo- 
graphs with respect to the stationery floating 
mark. The X-parallaxes are measured and di- 
rectly formulated to give height differences. 
The contours and profiles are plotted at twice 
the photographic magnification. Vertical and 
horizontal measurements are limited only by 
the SEM resolution. A relatively unskilled 
operatorcan operate this rather simple plotter. 
The Micro Surfer was developed on the ideas 
of Professor A. Boyde, of the University Col- 
lege London. 
DATA REDUCTION TECHNIQUES 
Both single-image and stereoscopic ap- 
proaches to photogrammetry were featured in 
the reports of the National Correspondents of 
Commission V. Considerable use is made of 
single-image photogrammetry in Austria 
where the light slit image method 
(Lichtschnittverfahren) is extensively used 
in profiling and cross-sectioning of railroad, 
highway, and street tunnels. Single-image 
photogrammetric measurement of the optic 
disc were made in Sweden by using the slit 
image method. Single-image photogram- 
metry was also applied in Sweden to athletic 
contests, and used in Hungary in a wide vari- 
ety of projects. 
One ofthe major trends in the development 
of non-topographic photogrammetry during 
the past four years has been the increasing use 
of analytical data reduction methods, as re- 
ported from Austria, Canada, Czechoslovakia, 
Finland, France, Hungary, Norway, Romania, 
South Africa, Sweden, the USA, and USSR. 
With little modification, many of the computa- 
tional methods which were developed over 
the years for aerial mapping and aerotriangu- 
lation can be applied in non-topographic proj- 
ects. 
Through the use of advanced analytical data 
reduction techniques, the use of non-metric 
cameras for data acquisition in close-range 
and micro-range photogrammetry hasbecome 
possible. A number of analytical data reduc- 
tion approaches, particularly suitable for 
non-metric photography, have evolved; the 
Direct Linear Transformation (DTL) ap- 
proachdeveloped inthe USA isacase in point. 
On-the-job calibration approaches and self 
calibration methods are widely used in con- 
nection with non-metric photography, as re- 
ported from Austria, Canada, Hungary, Po- 
land, Romania, and the USA. 
The use of advanced analytical data reduc- 
tion techniques also makes it feasible to solve 
some non-topographic problems satisfactor- 
ily by utilizing simple photogrammetric 
equipment (mirror stereoscope, parallax bar, 
etc.), as reported from Sweden. 
In applications where the point-by-point 
approach inherent in the analytical solution 
is not acceptable (e.g., in some aspects of ar- 
chitectural photogrammetry), the use of ana- 
lytical plotters combines in a most favorable 
way the advantages of both the analogue and 
analytical evaluations. Experiments are 
being carried out in Canada and Italy to eval- 
uate the advantages of analytical plotters in 
non-topographic photogrammetry, particu- 
larly in conjunction with architectural sur- 
veys. Analytical plotters also are used in 
Canada for data reduction from non-metric 
photography. 
In many areas of application of non- 
topographic photogrammetry, a digital model 
of the surface being mapped is often a more 
desirable product than the conventional con- 
tour map on account of its flexibility, whether 
one is interested in measuring the surface 
geometry or in evaluating the deformations 
and movement of objects. A digital model 
provides the user with almost unlimited flex- 
ibility in the use of the electronic computer 
for design and analysis. Mathematical model-