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
ro
la
m o
—
| |
oc ne
r^