Aerial photograph; Aerial photography
Photographs taken from the air are useful to archaeologists because they show information that cannot be easily seen at ground level. It has been carried out systematically the 1940s in the northeast - though there are earlier examples of note. There are three main types of patterns that aerial photographs can help identify.
Firstly, low angle sunlight can reveal patterns of earthworks in fields that are highlighted on one side and have a shadow on the other. Photographs taken can show the overall plan and often make much more sense of these features than could be gained on the ground.
Secondly, soil marks in ploughed fields can be the result of disturbed buried remains. Differences in soil colour can be seen from the air. Ploughed out walls of chalk, or heavily mortared, will colour the ground around them white.
Thirdly, buried remains can affect the way plants grow producing cropmarks, especially in particularly dry seasons when parchmarks are produced. These are due to the buried remains stunting or promoting enhanced growth of the crop dependent on the type of remains. These marks are easily seen from the air - but may only last a few days based on the weather patterns. Not all the 'site' may be revealed at once - and the total knowledge of a site might be the comprised of many years flying and photographs.
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