GREAT BRITAIN 3. 
mountainous areas, where control is sparse, are being mapped 
by slotted template and by adjustment of uncontrolled 
multiplex bridges graphically to perimeter control. 
Research into techniques is mainly concentrated on 
methods of rapid production of 1/50,000 maps in areas where 
access is difficult and consequently control is sparse. 
The Directorate houses the photogeological Section of 
the Directorate of Colonial Geological Surveys, and the 
Colonial Forestry Air Survey Centre. These Sections handle 
special problems and maintain touch with equivalent 
Departments overseas. Their needs for reconnaissance maps 
in unmapped areas are met by rapid sketch mapping or by 
quickly produced uncontrolled mosaics at aoproxiraately 
1/50,000 or 1/100,000. 
The Air Survey Company Ltd, has undertaken extensive 
photographic and mapping operations both in the United 
Kingdom and overseas (4)« During the past four years a 
total of 250,000 square miles have been photographed at 
scales of 1/20,000 and smaller, using both Williamson 
Eagle IX and Wild RC5A (150 mm.) cameras mounted in D.C.3» 
Anson, and Rapide aircraft. Navigational methods have 
been wholly visual. The principal areas of operation 
overseas have been East and Central Africa, Iraq, Libya, 
and Thailand. The Company also undertakes training and 
consultancy on behalf of overseas Governments. 
Mapping scales have ranged from railway engineering 
surveys at 1/480 scale to regular 1/50,000 topographical 
series, aerial triangulation and plotting being accoiqplished 
on Zeiss Stereoplanigraph CÔ, Kelsh, and Multiplex equipment. 
Film is used throughout, format 9" x 9 rt . Large scale 
plotting has been expedited by the use of aircraft capable 
of flying at very low speeds, whilst medium scale work has 
generally entailed the use of two types of photography, one 
at high altitude for aerial triangulation or intensification 
of ground control, and the other at medium altitude for 
plotting of detail and contours. Efforts have been made to 
reduce the amount of planimetric control required in 
undeveloped areas by the use of transverse small scale 
photographic tie strips. 
The Company undertakes airborne geophysical surveys,