25 
planimetric manuscript compilation from stereo models, orthophoto maps 
were made. Complete planimetry having been represented on orthophotos, 
stereo compilation was limited to the compilation of (10-feet) contour 
manuscripts". 
When comparing existing property boundary plots, that had been 
produced from field records for land tax surveys, with the contents of the 
photomap, “innumerable faulty records or record interpretations that hither- 
to had an appearance of finality and legality” were exposed ! 
As for the production of overlays: instead of scribing details onto a 
Contone scribing sheet which carries a positive copy of the orthophoto sheet 
(see section 1.5.5 above), in the US the overlays are often produced by 
digitising these details from the orthophoto sheet and subsequent automatic 
drawing. According to experience at the ITC (van Zuylen, ICA Commission 
III, Automation, Budapest, August 1973), digitising can be done in about 
45% of the time needed for scribing. 
3.1.4 United Kingdom 
In the UK, orthophoto mapping at 1:2,500, including contours at 1 
metre intervals, has been produced to cover the planned area of Stonehouse 
New Town (ref. Phot. Record, October 1973 and October 1974). “Aerial 
photography was especially flown for the project using a Wild RC 5 A 
(152 mm, 230 x 230 mm) camera. The contact scale was 1:10,000 and the 
flying was planned in east-west runs to cover each row of National Grid 
1 km x 1 km squares by single strips of photography (thereby providing a 
side-lap of about 56%). The camera was set to give a forward overlap of 90% 
between exposures. It was thus possible to select 60% overlaps, each of which 
contained the complete area of every proposed 1 km x 1 km sheet, thereby 
greatly simplifying the production of the orthophoto-map sheets by avoiding 
any form of mosaic assembly”. 
The planners used the photo maps together with the existing planimetric 
line maps at 1:2,500 produced by the Ordnance Survey. “The production of 
the orthophoto maps in the same format as the published 1:2,500 OS sheets 
enabled separate contour overlay transparencies to be readily produced for 
use with each of the two map series”.