countries in Africa, the Far East, the Pacific, the Caribbean and Central 
America. 
A large part of the Directorate's topographic map production is at a scale 
of 1:50 000. Since the last report over 460 500 km? was mapped at this scale and 
84% of this mapping is contoured with a 50 ft. or 20 m. vertical interval. In 
addition 16 580 km? were mapped at scales of 1:25 000 to 1:10 000; dual scale 
mapping, that is the production of two series (1:25 000 and 1:10 000) from one 
original, was also undertaken. Increasing effort continues to be devoted to 
large scale contoured plans of developing rural and urban areas; 465 sheets 
were produced at scales of 1:5 000 to 1:1 200 and 97% of this is contoured with 
vertical intervals ranging from 5 ft. to 25 ft. and from 2.5 to 5 m. 
Most of the mapping photography used by the Directorate is flown by 
commercial firms under contract, using Wild RC8 or RC9 cameras. Ground 
control is provided by the Directorate's field surveyors, using pre-marking 
techniques whenever possible. Semi-analytical aerial triangulation, using the 
aerotriangulation by independent models technique, has been increasingly used 
and is now the main method for all scales. Wild A9 and B8 plotters, both with 
automatic readout, are used to observe the aerial triangulation. Wild PUG4 
-. markers are used for the preparatory marking of points and a Bausch and Lomb 
2240 siereoscope is used in identifying control points. Most of the plotting is 
performed on Kern PG2 plotters, but Wild A8, Thompson Watts mk II, and 
Williamson multiplex plotters are also used. Mosaics and photomaps prepared 
from rectified air photographs are produced using a Wild E4 rectifier. 
The Land Resources Division, which until 1 April 1971 was part of the 
Directorate, but since then has been one of the scientific units of the 
Overseas Development Administration; has continued to undertake integrated 
resource and specialised surveys for developing countries. These surveys 
have made very extensive use of aerial photography. 
EDINBURGH UNIVERSITY, School of Built Environment 
The school made a photogrammetric survey of Dennis hess, North Ronaldsay, 
Orkney (128). 
FAIREY SURVEYS LTD 
Survey photography has been successfully carried out in countries outside 
the UK covering over 140 major projects. A wide range of negative scales has 
been obtained on these overseas operations, ranging between 1:5 000 and 
1:65 000. The countries served included Libya, the Trucial States, Saudi 
Arabia, Malawi, Zambia, Singapore, Malaysia, Australia, Honduras and States 
in the Caribbean. Amongst the larger flying contracts was the provision of 
Stereoscopic coverage at 1:30 000 contact scale of a single block of photography 
amounting to 100 000 km’ in Zambia. Also worthy of note was the taking of 
survey colour photography in Zambia - 2000 kn? in true colour and 6000 km? 
in false colour: 70 line km. of multi-spectral photograpny was also obtained. 
During the four year period at home, aerial survey flying operations were 
also continuous and over 400 separate photographic sorties were achieved in 
the United Kingdom. Generally speaking, the contact scales were larger in the 
UK than those obtained for overseas countries, but nevertheless covered a very 
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