EXPERTS from English Heritage are hoping to solve a small piece of the mystery surrounding the Roman site at Groundwell Ridge.

This week a team of archaeologists have been hauling highly sensitive radar equipment in straight lines on the 1.8-hectare site in a bid to get an idea of the structures lying several metres beneath the ground in North Swindon.

Excavation is due to begin at the site later this month.

Team member Paul Linford has visited the site on seven occasions.

He said: "This is a highly enigmatic site and there are many questions which remain unanswered. We have already carried out some basic tests using earth penetrating techniques.

"We definitely know that there are some high-value buildings here possibly a villa, but a hoard of coins found here several years ago could discount that.

"We believe it may have been a religious shrine and there is the possibility of Roman baths and some mosaics. But until we get these results, we aren't sure what to expect.

"We hope that the geophysical experiments will give an idea of the buildings arranged here, and where we should put our trenches when we begin excavating.

"It is far from an exact science and much depends on the soil conditions. The system works better in the wet and even better through ice, surprisingly."

In what can only be described as a Heath Robinson technique, one of the team pull along a device called Ground Penetrating Radar. This works on a similar principle to sonar waves of energy are beamed into the ground.

If those waves hit something solid they bounce back to a receiver, which times how long the wave took to bounce.

The depth at which the structures lie buried can then be gauged.

That information is then recorded into a computer on a wheelbarrow being pulled along by another team member. Once the whole site is surveyed, the results are sent to a laboratory.

There, the data gathered is lined up to produce a computer generated three-dimensional map and if all goes to plan, the archaeologists will be able to see the squared off walls of prominent buildings.

David Miles, chief archaeologist for English Heritage, said: "I am very excited that the geophysical survey has begun at Groundwell Ridge. It is an amazing site that we know very little about and we are looking forward to learning more.

"This excavation is a wonderful opportunity for English Heritage to work with the community in Swindon on a site that is as significant as any found in the country. Groundwell Ridge will become an outdoor archaeological laboratory that will be of interest to everybody."

A team of 15 archaeologists from the English Heritage Centre for Archaeology in Portsmouth will begin a five-week dig on the site soon. Five trenches will be excavated, based on information gathered from this week's survey.

In the TV spotlight

GROUNDWELL Ridge will be one of two archaeological sites in the country the other is at East Marton in Middlesbrough used to host this year's Time Team Big Dig over the weekend of June 28 and 29.

The Big Dig is a national archaeological event being organised by the makers of the programme.

They want to draw attention to archaeological digs all over the country and are asking people to dig metre or yard-square test pits, no more than 60cms (two feet) deep, and see what they find.

The Time Team event will be held slightly east of the English Heritage digging project.

Time Team will dig a series of test pits in a bid to discover how large the Roman complex may have been and what may have been going on around it.