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HYDROGRAPHIC DEPARTMENT, Ministry of Defence (Navy) 
Aerial survey is used in tidal stream and filtration studies, the plotting of tidal 
stream vectors being done with Wild A8 and EK22 equipment and automatic 
plotters (35). 
INSTITUTE OF HYDROLOGY 
In collaboration with The City University, work is in progress in the deter- 
mination of snow depth which, combined with density measurements and melt 
rates, will permit the estimation of water input to the catchments of the Rivers 
Severn and Wye and the modelling of melt water runoff processes (16,17). 
Zeiss (Jena) UMK 10/1318 and Wild P32 cameras and a Zeiss (Jena) Stecometer 
will be used to provide ground and snow surface co-ordinates in digital and 
graphical form. Field experience to date has been limited by a series of mild 
winters, 
UNIVERSITY OF LONDON: 
IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY, Department of 
Civil Engineering 
The displacements of points on a box girder under stress were determined 
from photographs taken with a survey camera mounted in a cradle which was 
suspended from a crane. As part of the same research programme, a 1:12 
scale model of a composite box girder bifurcated elevated motorway is being 
studied at both working and ultimate loads; again photogrammetry is one of 
the methods being used to monitor the behaviour of the steel plates. The work 
in both cases has been done in collaboration with University College London. 
The movements of points on an experimental embankment subjected to prolonged 
stress until collapse were evaluated from photographs. The collapse occurred 
at night when the points were marked by small lamps. From pairs of X-ray 
shadowgraphs of a model containing analogues of soil particles, the positions 
of tungsten marks on the particle surfaces were established. This enabled the 
rotation and translation in space of the particles under different conditions of 
stress to be deduced. Both of these projects were done in collaboration with 
City University. 
Procedures are being examined for establishing from pairs of convergent 
photographs the shapes of grains with maximum dimension of about 1 mm used 
for filter beds. 
UNIVERSITY OF LONDON: 
IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY, Department of Mining 
and Mineral Technology, Royal School of Mines 
A co-operative study with the Department of Photogrammetry and Surveying, 
University College London applied conventional photogrammetric techniques 
and terrestrial photography to various rock mechanics problems (130, 131). 
Measurements made of joint structures assisted in the design of large open 
pits. Observations of small rock movements over periods of time enabled the 
strength of rock faces, and hence the slope stability, to be predicted more 
accurately.