At first sight, archaeology may hardly seem the ideal place to look for the application of state-of-the-art computer technology. To the outsider, it appears a discipline that is too wrapped up in the past and too dependent on painstaking work with brush and trowel for automation to be of much use.
Yet archaeology is being revolutionised by new computing and telecommunications technologies all the same - in both the United States and Britain. The most startling proof of this is in the use of geographical information systems. GIS, as it is known for short, allows archaeologists to manipulate information about where things are located, and to reach insights that would be impossible or too time-consuming to achieve manually.
One of th more useful tricks of GIS is "viewshed analysis", which is the precise measurement of the visibility of ancient monuments in the landscape. This is based on the idea that prehistoric monuments were built to be seen, and to communicate messages - for example about the location of territories or sacred places. The more visible the monument, the more public the message was intended to be.
GIS software is loaded into a PC, together with digital landscape information hired on disk from the Ordnance Survey (which contains data on contours, heights and obstacles). The grid references of monuments in the landscape and the height of the hypothetical viewer are then added.
Maps are produced of every point from which the monuments could be seen at a given date. By meshing the viewsheds of different monuments together, archaeologists can draw inferences about the most and least "public" parts of the prehistoric landscape.
In a recent study of prehistoric rock carvings in the Kilmartin Valleyin Argyll, Dr Vince Gaffney, of Birmingham University's Field Archaeology Unit, and Professor Richard Bradley of Reading University used the technology to identify a difference between the visibility of complex and simple examples of rock art.
They found that monuments with elaborate carvings - both natural rock formations and standing stones - were highly visible, mainly from the direction of the Crinan estuary, the principal entrance to the Kilmartin valley from the south. This suggested that they were intended, like modern advertising hoardings, to communicate public messages, perhaps about the ownership of the valley, to outsiders.
Simple examples of rock art, however, were found to be largely invisible from a distance, implying that they were designed to communicate only intimate messages with passing travellers, perhaps about rituals to be performed before going on.
A second use of GIS technology lies in "cost surface analysis": the examination of the time it takes to walk ove different types of terrain. Cost surface analysis has mainly been used in archaeology to determine a site's "catchment area", or the area of land surrounding and belonging to a prehistoric settlement.
It has long been assumed that in ancient farming societies farmland generally extended no further than about three miles (five kilometres) from a settlement - a comfortable distance for a farmer to walk to his fields. On this basis, archaeologists have drawn circular catchment areas of 5km radius around settlements on their maps.
In reality, however, catchment areas are never perfect circles, but irregular shapes of different sizes, because where the terrain is difficult, a farmer can travel a shorter distance in a given time. …