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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
The study of ancient fields in England is more than just one aspect of ancient 
agriculture, though it is a very important aspect. In areas where such remains 
are traceable it is one of the best approaches to the whole problem of where 
human beings lived at different periods and what their countryside looked 
like. Detailed investigation at a number of points is ultimately vital, but the 
main virtue of the study is that it essentially involves us in considerations not 
only of individual sites, but of whole landscapes. For this, air photographs are 
essential. They provide the panoramic view that is necessary and are the only 
effective means of plotting crop-marks and areas of partial obliteration. 
Their importance can be demonstrated by a brief review of the nature and 
extent of ancient fields in England and the problems of recording which they 
present. “Celtic” fields, which began in the Early Bronze Age but reached 
their greatest extent in the Romano-British period, are our earliest recognisable 
remains. Most are to be found on downland slopes where the cutting action 
of the plough and the movement of ploughsoil has created scarps, which we 
call lynchets, along the field edges. Such remains can present dramatic pictures 
to the spectator on the ground, but these are essentially very restricted views of 
sometimes untypical areas of field development whose steep situation, moreo 
ver, adds difficulties to ground survey. Many continuous areas of “Celtic” 
fields in the south of England cover more than 500 acres and we know of one 
covering more than 2,000 acres. Such fields may be found on valley bottoms 
and hilltops as well as hillsides and face all points of the compass. It is only on 
northern slopes, so often in shadow, that the aeroplane sometimes fails to help. 
Even this is rare, but serves to emphasise the vast difficulties of dealing with 
these remains without the help of air photographs. 
Low level oblique views lift our line of sight to see much more fully than from 
any point on the ground the extent and nature of the remains while not losing 
our sense of immediate recognition. The vertical high-level photograph takes 
in a much greater area, including parts where later ploughing may have 
partially or completely obliterated any surface relief, and presents it all to us 
at a roughly constant scale. We are thus enabled to produce plans to an accept 
able accuracy at a small scale (usually 1 : 10,000) by using only simple methods 
of transcription. To do this by ground survey alone would take a very long 
time indeed. Conversely, it must be stressed that ground checking wherever 
possible is quite vital and that large-scale plans of small areas are often highly 
desirable and need to be made on the ground. In certain areas, however, it is 
air photographs alone that can produce for us plans of ancient fields which 
have totally disappeared from ground view. These are notably in the east 
English Fens where in the Romano-British period, as in later times, it was 
essential to drain the area to make cultivation possible. Most boundaries were 
therefore marked by drainage ditches and today these can be seen as crop- 
marks (fig. 1). It is precisely because such ground is usually flat with no points 
of observation that we need an aeroplane even to realise that there is a pattern 
made in the corn. 
So far we have seen that air photographs are virtually essential to a study