22 
vectors can be obtained, and thence the strain. This technique has been applied 
to the measurement of surface displacement, strain, and creep in plastic 
materials, and to the opening and closing of a weld crack when put under stress. 
Masked aperture cameras have been developed for recording grid patterns on 
35 mm film with 300 lines per mm resolution. When two such grid patterns are 
compared, separate Moire fringe maps are obtained for both vertical and 
horizontal displacement. The method can be adapted to yield longitudinal 
displacement or contouring information. Using this technique, measurements 
have been made of the deformation of large concrete girders and brick lintels 
(33). 
UNIVERSITY OF NEWCASTLE UPON TYNE, Department of Surveying 
Research work has investigated the problem of orientation of the head, which is 
a major problem in photogrammetric studies of facial change (110). 
UNIVERSITY OF NOTTINGHAM, Department of Civil Engineering 
An investigation into the application of a topographic plotter to scanning electron 
microscope image analysis was carried out (151). 
ORDNANCE SURVEY 
A major investigation of instruments and methods for aerial triangulation 
concluded that aerial triangulation by observation of independent models on 
precise plotting machines would be an acceptable alternative to the current method 
of analytical aerial triangulation when the existing stereocomparators require 
renewal. The capture of contours in digital form at the stereoplotting stage has 
received some attention; this will increase in 1976 with the purchase of a 
magnetic tape interface for use with the Wild A10 and EK22 equipment. 
As a result of an investigation of instruments for the contouring of derived maps, 
7 Kern PG2 stereoplotters have been purchased for that purpose, and they may 
eventually also be used for 1:2500 scale resurveys. Three Zeiss (Oberkochen) 
Planicarts have also been purchased for use on the full range of Ordnance Survey 
tasks. An alternative graphical method of resurvey for 1:2500 mapping of rural 
areas, using rectified enlargements and controlled by ae rialtriangulation has 
been tested and used for limited production work. 
An important innovation in the photographic studio has been the introduction of 
automatic processors for both air film and paper prints, providing consistent 
output at reduced costs. Considerable effort was expended in determining 
optimum processing conditions for the new equipment. The implications of the 
closure of the only British factory producing diapositive glass plates, forcing a 
choice between film and imported plates, were still under investigation at the 
end of 1975. 
ROYAL AIRCRAFT ESTABLISHMENT, Instrumentation and Ranges Department 
The work at RAE on the development of optical transfer function (OTF) methods 
for the specification and assessment of image quality in optical systems has been 
applied to air survey lenses (11, 26, 96, 97, 98). This work has included a 
study of the reproducibility of OTF measurements (by investigating the sources 
of error in such measurements and by a comparison of results obtained on a 
  
  
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