Terrestrial Geophysics Blog

Welcome to the Anomaly: Geophysics Blog

Bartington gradiometer in actionBartington gradiometer in actionWelcome to the blog of the Terrestrial Geophysics service here at Wessex Archaeology. As this is our first post, we should start by introducing ourselves and what we do.
 
The Terrestrial Geophysics service is led by Paul Baggaley, our Geophysics Manager; he's also in charge of the Marine Geophysics service. Ben Urmston is responsible for leading teams in the field, and is involved with the majority of the fieldwork.
 
Since going ‘live' back in January, when we began advertising commercially, we've carried out work all around the southern half of the country. Most of our work comes from new developments of houses, roads and so on. The developers have to make sure that any archaeology that might be damaged during construction is checked out and excavated if needs be.
 
Sometimes the areas that are being developed are huge and, for a long time, the only way to find previously unknown archaeology was to dig lots of trenches and hope that at least some might cover the archaeology. To make this job of finding sites easier and more reliable, geophysicists use instruments that can detect archaeology without having to dig it up. We apply different methods depending on whereabouts in the country we are, and what we might expect to find. Each has its own benefits and drawbacks, so we need to choose the equipment carefully to provide the archaeologists with the right information.
 
This blog has now been combined with our main news blog.
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What about the Geometrics

What about the Geometrics proton and/or Cesium precession gradiometer systems? Ar they better or worse than the Bartington?

Hello and thanks for your

Hello and thanks for your interest!
 
In a nutshell, the Bartington gradiometers use fluxgates, a different type of sensor to the GeoMetrics magnetometers, and each has its own strengths and weaknesses. In archaeological geophysics, their application is generally quite similar, especially when total field instruments are arranged as gradiometers. It’s not easy to say if one is better, as they collect different types of data, although it’s worth making a couple of points.
 
Total field instruments, like the GeoMetrics magnetometers, are generally more sensitive than fluxgate models. The extra sensitivity comes at a price, however, and the fact that fluxgate instruments are so affordable is probably the main reason that they are widely used in archaeological geophysics.
 
Another good reason is that most large archaeological features produce anomalies much stronger than the magnetic background, and well within the sensitivity range of fluxgate instruments. Trying to detect small or weak features is easier with greater sensitivity, but the difficulty then becomes reliably distinguishing such weak anomalies from the general background.
 
We’ve touched on some interesting themes here; I’ll try to follow these up in the near future.

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