Ordnance Survey International

Ordnance Survey International, former surveying, mapping, and aerial photography agency (1946–2001) of the British government, which provided advice on technical matters concerning all aspects of surveying and mapping. The maps created by the agency were produced using aerial photography and photogrammetric methods. Aerial photography missions were flown mainly by air survey companies of the United Kingdom, and surveyors were sent overseas to establish horizontal and vertical ground control for the photography. After maps were compiled...