(70) 
réseau for the elimination of the effects of film distortion, thus making it pos 
sible to use film cameras for work of the greatest accuracy. For this, if for no 
other reason, it is felt in Great Britain that the work is a valuable and original 
contribution to Photogrammetry, deserving study. 2 ) 
Investigations have been made into the possibilities of reducing the com 
puting time by the employment of electronic methods. The results achieved 
are extremely encouraging and it is hoped that before long the computations 
will be done in this way. 
It is well known that there is great difficulty in securing a satisfactory 
lateral overlap in flying for photography at very large scales. All the flying for 
Ordnance Survey photography at large scales has made very successful use of 
the Decca radar navigation system, 
The Colonial Survey Directorate. 
The Directorate of Colonial Surveys is always considering developments 
in its methods and much work has been done on the adjustment of strips and 
blocks of photographs. An interesting piece of work is the construction of a 
three-projector multiplex unit (in conjunction with the Ministry of Supply and 
the Williamson Manufacturing Co.) to facilitate the absolute orientation of 
awkwardly placed photographs. 
Hunting Aerosurveys. 
Reference has been made to the large scale methods developed by this firm 
and to the use of photogrammetry in constructing ground profiles. 
For mapping at the scale of 1/50.000 this firm uses a combination of the 
Multiplex and the Wild A6 plotting machine. It is found that for spanning 
distances up to six overlaps in width the Multiplex is sufficiently accurate at 
this scale and considerably quicker than the more elaborate instruments. On 
the other hand Hunting Aerosurveys Ltd. find it unsatisfactory for detail and 
contour plotting in that it will not plot at or near map scale; it is trying to the 
operator’s eyes; and the image is not sufficiently well defined for good inter 
pretation. The A6 is therefore used for detail plotting to control provided from 
the Multiplex. 
The Air Survey Company. 
The Air Survey Company has been carrying out research for the Ministry 
of Supply on film distortion and humidity control in air cameras. 
Williamson Manufacturing Co. Ltd. 
The Williamson Manufacturing Co. have re-designed their Multiplex 
equipment and the new model is being exhibited at the Congress. A new 
camera, the Eagle IX Mark II, fitted with the new Ross distortion-free (less 
than 10 microns) lens has been developed. 
Development is progressing on a fully automatic rectifying enlarger and a 
large scale plotter. Investigations are being made into devices for the compen 
sation of image movement and for the recording of tilt in the air. 
2 ) E. H. Thompson, The Journal of the Institution of Chartered Surveyors March 1951. 
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