Radar reveals Roman secrets

Archaeologists discovered that a Roman settlement in Wroxeter, Shropshire was as big as Pompeii - without touching the ground that covers it. They used ground-penetrating radar, coupled with magnetic and electrical analysis of the soil, to draw up a plan of the fourth-largest city from Roman times.

The first views of the settlement, occupied for 300 years after the Romans left Britain in the first century AD, were drawn up from aerial photographs taken in the years after the Second World War. But two years' work by University of Birmingham researchers has discovered that what used to be thought of as a village was a city covering 78 hectares and that a substantial portion was wrecked by a fire which destroyed many of the timber-framed houses.

"There is still a place for spades in archaeology," said Simon Buteux, who led the research, which was done by an international team of scientists. "These techniques give you images and a plan, but it's not like coming into contact with the real thing.

"However, the new techniques do have the advantage that they do not move any of the buried items. In the process of excavation, archaeologists destroy much of their evidence, even as they seek to record and understand it," said Mr Buteux. The newer techniques reduce the cost and avoid the destruction of excavation. Previously, only 5 per cent of the city had been excavated, principally its public baths. Now 80 per cent has been investigated, leading the scientists to triple their estimate of the number of people who lived there.

Ground-penetrating radar can detect objects at a range of depths, varying from 15 to 150cm below the present ground level, where the foundations of Roman Wroxeter are found.

A similar technique was used to detect an older version of the Great Wall of China from the space shuttle last year.