The mountain and moorland areas are being entirely resurveyed at the 
1:10 000 scale, of which 17 500 km? have been surveyed in this four year period. 
In addition a further 3800 km^ were surveyed at the former scale of 1:10 560. 
In conjunction with this programme small enclosures of rural mapping, 
totalling 2300 km” within the mountainous blocks, have been resurveyed at 
1:2500 scale. 
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It should be noted that the 1:10 000 series provides complete coverage of the 
country and is derived from larger scale maps where these are available; it is 
also the largest scale at which contours are shown. Consequently a separate 
operation is needed to add contours to the derived maps; except in very flat 
areas the standard method of supplying contours is by stereo-plotting machine 
and 17 900 km? have been contoured during the period covered by this report. 
Two vertical intervals are used in the metric scale; 5 m for the majority of the 
country but 10 m in the more mountainous areas; these replace the 25 ft interval 
formerly used in all areas. 
The Department carried out all stages of the aerial survey, including flight 
planning, taking and processing the photography (which includes infra-red for 
tidal surveys), aerial triangulation where required, instrumental or graphical 
plotting and field completion. Aircraft and crews are hired from commercial 
companies each year for seven months from about March to October but the 
Department provides its own camera operators and cameras. Five aircraft, 
flying a total of about 1000 hours per year, are now employed on this work. 
The photography is acquired using four Zeiss RMK30/23 cameras, three 
Wild RC8R cameras and one Wild RC10 camera, the latter having both wide 
angle and super-wide angle lens cones. 
The stereo-plotting equipment used includes eleven Thompson- Watts, 
twelve Wild A8 Autographs, two Wild A10 Autographs, one Santoni 
Stereosimplex and two Santoni Stereomicrometers; a further four instruments 
are employed in the training wing. Where required rectified enlargements are 
made on two Zeiss SEG V Rectifiers. Analytical aerial triangulation is carried 
out using three Hilger and Watts recording stereocomparators, the observations 
being processed on the Department's ICL 1904 computer (170). This computer 
has recently replaced an ICL 1902S computer which was bought and subsequently 
replaced within the four year period of this report. 
ORTHOPLAN LTD 
This company was formed in April 1971. It is affiliated to a French company 
called Cabinet Yanmoerbeke of Tourcoing and Roubaix. Its equipment includes 
an SFOM A90 plotter, a D693 orthophoto device, an automatic drafting table, an 
IBM 1130 computer and a Geodimeter 6. The company will operate in UK the 
Commonwealth, South Africa and USA and specialise in surveys for highway 
studies, planning and development, forestry, water supply, drainage and land 
reclamation. 
ROYAL COMMISSION ON HISTORICAL MONUMENTS 
Two air surveys are being prepared, one at 1:5000 and one at 1:500 for the 
Commission archaeologists. 
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