ON NEW ARCHAEOLOGICAL TECHNOLOGIES:

What lies beneath
Oct 2nd 2003
From The Economist print edition

New �non-destructive� sensing technologies are transforming archaeology

SINCE its emergence as a science, archaeology has wrestled with a paradox: discovery involves destruction, and investigation requires intrusion. An archaeological dig cannot be undone. Once a layer has been stripped away, any information not recorded is lost. Most archaeologists have had the experience of trying to discover something new about a site that has been completely excavated, only to find that the question they wanted to ask had not occurred to the original diggers.

So knowing what lies beneath the surface before the trowel hits the soil has long been the dream of many an archaeologist. As well as saving time in determining where to dig, it would enable archaeologists to answer questions with a minimum of destruction�and potentially none at all. This dream is slowly becoming a reality, as a result of improvements in non-destructive surveying techniques. Archaeology has never been a wealthy discipline, but by borrowing tools developed for more well-endowed professions, archaeologists are developing X-ray vision�or, to be precise, infra-red, microwave and magnetic vision, which are even better.

Such tools enable archaeologists to identify and target small areas of interest, and to move away from the complete excavation of sites towards a more selective approach. This method, known as the �conservation model� of archaeology, means that archaeological resources are maintained for future generations, who will be armed both with novel technologies and new questions. As sensing techniques improve, archaeologists are also benefiting from the tumbling price of computing power, which enables them to combine, overlay and analyse data from multiple sources, yielding further insights.

Seeing through new eyes

To demonstrate the potential of such techniques, a group of archaeologists from the University of Arkansas, led by Fredrick Limp and Kenneth Kvamme, have been investigating the site of Army City in Kansas. Established in 1917, it was a bustling town, complete with hotels and theatres. In 1921 it burned to the ground, leaving no trace of its former existence. Or so it appeared. But last year, when the archaeologists began to map what is now an empty hayfield, they found that they could see the precise locations of roads, pavements and rooms of buildings. They could even trace the sewage system. �It was almost as though the soil was transparent,� says Dr Limp.

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Another technology that archaeologists are taking to is thermal imaging. This employs high-resolution cameras that are sensitive to the so-called near infra-red. This part of the infra-red spectrum, with wavelengths close to that of visible light, carries heat energy. Thermal imaging thus records slight differences in temperature. Such differences at the surface are often tell-tales of what lies beneath. A stone foundation, for instance, retains heat differently from a pit that holds moisture.

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Such advances in sensing techniques are certainly welcome, and are helping to change the nature of archaeology. But Dr Limp reckons that there is just as much scope for improvement in using computers to integrate different sorts of observation. He and his colleagues have made a start on this at Army City, where they are creating a system that will swallow, digest and combine data from satellites, aircraft and ground-based sensors, aligning them in a single, computer-based model of the site. The system, he says, should be fully functional next year.

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