What Exactly Is 'Geophys'?

Geophys (or geofizz as those in the know call it) is short for Geophysical. Geophys is all about creating underground maps of an area, like the one in our picture.

This is a geophys image of the Northborough site. Can you see the circular enclosures?

There's a Roman dyke running through the centre too.

© GBS Prospection Ltd and courtesy of Time Team.

By underground map we don't mean a map showing you how to find the best rabbit holes, but an archaeological underground map, a map showing the outlines and shapes of underground remains.

We had a chat with John Gater who was doing the Geophys for Time Team the day we visited. There's a picture of John at the bottom of this page.

What's Geophys all about then?

"Basically what we do is we use a series of instruments to actually map the buried archaeology, so the archaeologists know exactly where to dig. We can provide them with targets very quickly."

This is an H-Frame, just like the one used at Northborough. It's name is a 'Bartington Grad 601-2 Magnetometer'.

© GBS Productions Ltd.

What do you mean by 'instruments' - we're not talking about violins and recorders here are we?

"We've got a couple of instruments we use, one is a magnetic imager a bit like a metal detector but a lot more sophisticated. That's this H-Frame, it's like two fluorescent tubes with a box of electronics in between."

What do you do with it?

"You just walk up and down over a regular grid, taking readings at 25cm intervals. We take tens of thousands of readings over the whole field then process the results on the computer.

It actually gives us a picture of the reaches of the causewayed enclosure. The burnt tops of the ditches are what cause the changes in the magnetism, that's what we detect."

Here's John in Bath with another geophys instrument. This one is good for mapping out Roman villas and remains like that.

© GBS Productions Ltd.

I understand that with this site there was an aerial photograph taken in the mid-nineties that gave you a clue.

"That's right, it was a wonderful clue, we worked on that initially. It was very clear on one side of the site but on the other it's actually buried beneath alluvium, thick flood deposits, and they mask it from aerial photographs.

We can actually see beneath alluvium. We can still detect the ditches so if there are any gaps in aerial photographs we are able to fill in vital details."

So, geophys is a very useful tool for archaeologists, kind of like having bionic eyes!