Shadows cast by ruined walls or barely-perceptible variations of topography can make sense when the pattern is seen from an altitude of a few hundred metres. Moreover, buried archaeological remains can affect the growth or colouring of both grain and root crops, revealing the presence of settlements and sites of various kinds which have otherwise virtually disappeared through ploughing or other forms of erosion. Thus the defensive ditch of a Bronze Age settlement, seen from above, can be recognized by more dense and dark vegetation growing above the deeper, damper and more fertile soil with which the ditch has become filled over the centuries. Within such sites the outlines of vanished buildings of wood or stone can sometimes be recognised through similar effects.
In this and other ways, aerial survey and air photography provide a unique perspective that can capture both panorama and detail, and so provide a more complete picture of the past.
History of archaeological air photography
After World War II aerial archaeology became an integral part of scientific research in western Europe. Many photographs were taken specifically for archaeological purposes. Most were ‘oblique’ views taken at an angle from light aircraft to show archaeological sites to their best effect. At the same time, in many countries of the world, ‘vertical’ photography came into use for a variety of purposes. In this technique photographs are taken from specially adapted aircraft, looking straight down and recording the whole of the landscape rather than small parts selected for their archaeological content.
Vertical photography is widely used in landscape studies of all kinds, for instance in the geo-sciences, natural and historical heritage protection, and the creation and updating of maps. As a result, many institutions and organizations own impressive archives of aerial photographs made in different seasons, from various altitudes and in differing lighting conditions. These archives can become a rich source of heritage information when studied in a systematic way by archaeologists. Vertical photographs taken for military purposes, but now declassified and available to archaeologists, can be just as effective in providing new information both about archaeological sites and landscapes and about landscape change in recent times.
In addition, recently declassified satellite imagery offers new and exciting opportunities for archaeologists, especially in countries where access to conventional air photography is difficult. Satellite images taken in the 1960s and 1970s by American and Soviet military authorities have now been declassified and are available to researchers.
More recently, higher-resolution satellite imagery is proving especially valuable to archaeologists, though the cost of obtaining images is high. Perhaps institutions in Armenia could work together to acquire new satellite imagery or to share use of images that already exist. Parts of Armenia have been recorded by the Ikonos-2 satellite with a ground resolution of as little as one metre (link to web site). Use of such images could facilitate the first stages of survey in areas identifies for future archaeological reserch.
Making archaeology from air photographs
Vertical and oblique air photographs, and satellite images, show archaeological features at different scales and in different ways according to lighting and time of year. The information from these different sources needs combining in the form of maps and written records for communication to other archaeologists. This is usually done by interpreting and mapping the evidence to show sites and landscapes against backgrounds of topography or modern features.
This type of work has a history almost as long as that of aerial photography, and began when O.G.S. Crawford in Britain mapped parts of a pre-Roman field system in 1924. A small amount of mapping was done from that time onwards
In the 1960s the rapidly increasing number of air photographs taken in Britain each year began to raise problems of how best to manage the new evidence. The mapping of sites, especially those under threat of destruction, became an increasingly common procedure from this time. Methods used at this stage were entirely ‘manual’ and mapping was tedious and time-consuming. A major advance was made in the 1970s by Irwin Scollar, an American working in Germany. Scollar began using computers to transform aerial photographs to match maps. This led the way to the current phase of work in Britain where mapping, by entirely digital methods at scales of 1:10000 to 1:2500, is seen as a normal means of depicting the archaeological evidence and communicating it to other users.
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