Aerial Photography
Aerial photography is one of the best ways of understanding archaeological landscapes, because it reveals and makes sense of features which are too faint, too large or too discontinuous to be appreciated at ground level. These can occur as earthworks, cropmarks, soil marks or parch marks. There are three main elements to aerial photographic research: reconnaissance (actually flying and taking the pictures), archive search (examining pictures taken previously of a site or area, sometimes repeatedly over many decades), and mapping (where the information in aerial photographs is interpreted and correctly positioned).
Two types of aerial photograph are taken - vertical and oblique. Vertical photographs are often taken at high-level (upwards of 1000 feet), continuously with machine cameras mounted on the underside of aeroplanes flying in straight regular traverses. Many were taken in the 1940’s for military purposes. Oblique photographs are usually taken with a hand-held zoom camera from closer to the ground, at an angle to the site in view. Oblique photographs are taken ‘actively’ when the photographer has positively identified a subject; vertical photographs are usually ‘passive’ in that they produce blanket coverage with no specific archaeological bias.
Aerial photography revolutionised landscape archaeology in the twentieth century. Beginning with balloon flights in the early 1900’s, and expanding using open-seated biplanes in the 1920’s and 30’s, the entire UK now has almost continuous coverage, sometimes many times over. Systematic archaeological aerial survey has been carried out by organisations such as the Royal Commission on Historical Monuments of England (RCHME), now English Heritage, Cambridge University Committee for Aerial Photography (CUCAP) and many other public and private bodies. Helicopters are sometimes used as an alternative to fixed-wing aeroplanes, having the advantage of being able to hover in mid-air over a site. Archives of aerial photographs are held by English Heritage, RCHMs in Scotland and Wales, universities and local government archaeology services across the UK. Some of these collections are now accessible via the internet.
Further Reading:
D.R. Wilson "Air Photo Interpretation for Archaeologists" (Batsford, London, 1982).
