Four Zeiss (Oberkochen) RMK 30/23, one Wild RC10 and three Wild RC8R air 
cameras are used. Processing is now generally performed using a Pakorol 
automatic film processor, although hand processing is still carried out 
occasionally. Other photographic equipment includes three Cintel electronic 
contact printers, a Wild U4A transformation printer, a Kodak 242A automatic 
paper processor, and two Zeiss (Oberkochen) SEG5 rectifiers. Analytical aerial 
triangulation employs three Hilger and Watts stereocomparators, with preparation 
work by Wild PUG4 and PUG2 point transfer devices, a Cambridge stereo- 
comparator and various scanning stereoscopes. Stereoplotting equipment 
comprises 11 Thompson-Watts plotters for various focal lengths, 12 Wild A8 
and two Wild A10 Autographs, three Zeiss Planicarts and seven Kern PG2s. 
Four further plotters are employed on training. 
ORDNANCE SURVEY OF NORTHERN IRE LAND 
The main effort of the Ordnance Survey of Northern Ireland is directed to bring- 
ing the large scale mapping of the country onto Irish Grid sheet lines by 1980, 
up-dating the map series at basic scales of 1:1250, 1:2500 and 1:10 000 by both 
resurvey and revision methods. The resurvey part of the operation depends on 
the output from three Wild A8s. A Wild B8 is used to produce 10 m vertical 
interval contouring for the 1:10 000 series. By the end of 1975 about 1360 km? 
out of a projected total of 2465 km^ scheduled for resurvey at 1:2500 scale had 
been plotted, together with 5 km^ at 1:1250 scale. The 1:10 000 scale contouring 
task involves some 13 500 km? of which approximately 1040 km^ had been 
plotted. Absolute orientation on the Wild A8s is now performed analytically on 
the Hewlett Packard 9810A calculator, halving the time formerly taken. It is 
intended that this machine will also be used for aerial triangulation by independent 
models. 
Apart from its continuing nationaltask, jobs for other government departments 
have been undertaken, including 1 m interval contouring at 1:2500 scale, The 
Wild B8 has been used experimentally to plot demarcation lines between 
different tree species in plantations owned by the Forestry Division, Department 
of Agriculture. 
Photography for OSNI projects was originally secured through contracts with 
commercial firms. Since 1974 vertical photography has been taken with a 
Wild RC5 camera owned by OSNI and fitted to a Piper Aztec aircraft chartered 
from a local company. 
PHOTARC SURVEYS LIMITED 
Aerial photography has been used for topographic mapping for route planning at 
1:5000 and 1:2500 scales, and for engineering surveys at 1:500 scale for develop- 
ment and route design. Topographical surveys for route location have also used 
terrestrial photogrammetry. 
POTATO MARKETING BOARD 
Air photographic surveys at 1:7500 scale are made annually over certain arable 
areas of Great Britain to aid work already done on the ground in connection with 
the measurement of potato acreage. 
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