Magnetometry We use a Bartington 601 Gradiometer. We chose this one because it has a 1m separation between the sensors which increases sensitivity, the downside of which is that you detect metal fences easier too. It is quite easy to set up and use. The main problem we have with it, is being able to read the instructions on screen when we've taken our glasses off to reduce our magnetic signatures! |
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Software converts these numbers into colours or shades of grey so you can see shapes appearing in the results. The things that a magnetometer detects are those with a strong magnetic signal, every cast horse shoe or nail made of iron will be a blip, every gold brooch will be missed! Archaeologically, burnt things such as kilns or hearths or even bricks to some extent, have a strong signal. Local natural rock used for building won't show up but for some reason the natural processes of decomposition produce magnetic signals, so ditches that have been open for a while before infilling show up, whereas graves that are dug and filled in soon after don't. What you end up with is a picture like this:
which shows a portion of a circular
ditch next to a rectangular ditch enclosure. |