60
The second engineering application which
Cheffins (1975) described concerned the def-
inition of the complex shapes of a steel re-
spirator mould. Photography and plotting
both were achieved with a modified William-
son multiplex unit (described by Cheffins
and Clark, 1969) which allows the reprojec-
tion ofadistortion free 1:1 scale stereomodel.
During the period under consideration,
Grün and Stephani (1974) published an ac-
count of a photogrammetric survey of a Ger-
man atomic reactor and they reported that
standard errors of + 1 mm in plan and + 2mm
in height were achieved when a maximum
object distance of 10 m was involved. Some
years ago, Fairey Surveys Ltd. were active in
a similar field and, although no results were
published, a personal communication from
Cheffins (1967) gave some details. In the
course of designing reactor vessels for nuc-
lear power stations, the Central Electricity
Generating Board constructed and tested
model pressure vessels. During the testing
procedures, it was necessary to measure sur-
face distortions which took place in the vicin-
ity of 1 m diameter panels which contained
several nozzles. A panel was located on the
underside ofa vessel which was3 m in diame-
ter and more than 13 t in weight. The vessel
was installed in a pit for safety reasons and for
some of the trials it was subjected to high
temperatures as well as to high pressures,
which made direct measurement of a test
panel difficult if not impossible. Stereoscopic
photography was taken by phototheodolite at
two successively occupied camera stations on
the floor of the pit and with the camera axis
pointing vertically upwards. Later, a pair of
suitably modified Kelsh plotter projectors
were used to acquire photography. Co-
ordinate analysis was carried out on a Wild A8
with machine co-ordinates transformed to a
control system in the object space.
One of the most fruitful fields of applica-
tion for close-range photogrammetry lies in
the analysis of models. In engineering, a
number of interesting examples have been
reported. Particularly noteworthy is the cen-
trifugal testing of soil models, initiated by
Professor A.N. Schofield at the University of
Manchester Institute of Science and
Technology. Photogrammetric aspects of
these tests were reported by E1-Beik (1973).
They began in 1969 and serve to obtain pre-
cise measurements of surface movement of
soil models which rotate in a centrifuge at
speeds up to 45 ms~1. Tests are monitored by
closed circuit television and, at appropriate
or critical stages of a test, a pair of Zeiss (Jena)
UMK 10/1318 cameras can be lowered into
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1976
the centrifuge in order to take survey photo-
graphy. Synchronised with the two cameras
is a powerful high speed flash unit which pro-
vides 100 J for 2.5 us. The accuracy of meas-
urements is claimed to be about + 0.2 mm
which is considered to be acceptable.
Butterfield et al. (1970 and 1972) and An-
drawes and Butterfield (1973) have made use
of false parallax techniques in their studies at
the University of Southampton in soil
mechanics and in simple channel flow in
hydraulic experimentation. The fluid surface
was enhanced by paper tape punchings so as
to improve stereoscopic pointing. Similar
work is reported from the University of Bris-
tol in Dowman (1974) and from Switzerland
by Schmid (1973).
In this section of the paper, it has been
possible briefly to review photogrammetric
activities in branches of engineering which
include marine structures, dam displace-
ments, scarp erosion and rock face instability,
snow depth measurement, aircraft vent de-
formation and respirator mould shape, atomic
reactor geometry, and soil and hydraulic
model behaviour. These applications of
close-range photogrammetry have involved
research establishments, commercial com-
panies, and university departments. Some of
the British survey companies already have
received specific mention but others also are
involved in close-range applications, notably
Meridian Airmaps Ltd. who have carried out
tunnel surveys, bridge surveys for restoration
work, landslip analysis and displacement
measurement of earth retaining banks.
Photarc Surveys Ltd. has been formed since
1972 and this company has a special interest
in close-range engineering photogrammetry.
There will be more to say about the contribu-
tion of the commercial survey companies in
the concluding section of this paper. How-
ever the author would now like to turn to
some projects with which he has been in-
volved at University College London.
BUILDING AND STRUCTURAL ENGINEERING
Figures 2 and 3 show examples of precast
concrete panels which were contoured at 2
mm vertical intervals in order to show the
extent of deformation from an ideal plane sur-
face. Figure 4 shows a building constructed
of precast units and Figure 5 illustrates the
deviations of panels from the vertical in that
building. This kind of information on man-
ufacturing and erection tolerances was pro-
vided for the Building Research Station be-
tween 1961 and 1963 at a time when solutions
were being sought for these construction
