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Time slice from 23 to 25ns. This last slice is now practically all blank, but a few of the walls are still showing highly.

How deep are these pieces? Unfortunately, the software application I have access to makes estimating the depth a little challenging. If, nevertheless, the leading 3 slices represent the ploughsoil, which is most likely about 30cm think, I would think that each piece is about 10cm and we are only getting down about 80cm in total.

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Luckily for us, the majority of the websites we are interested in lie just below the plough zone, so it'll do! How does this compare to the other methods? Contrast of the Earth Resistance data (top left), the magnetometry (bottom left), the 1517ns time piece (leading right) and the 1921ns time piece (bottom left).

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Magnetometry, as discussed above, is a passive strategy determining local variations in magnetism against a localised no worth. Magnetic susceptibility survey is an active strategy: it is a measure of how magnetic a sample of sediment could be in the existence of a magnetic field. Just how much soil is tested depends upon the diameter of the test coil: it can be extremely small or it can be relatively big.

The sensing unit in this case is very small and samples a small sample of soil. The Bartington magnetic vulnerability meter with a big "field coil" in usage at Verulamium during the course in 2013. Top soil will be magnetically enhanced compared to subsoils just due to natural oxidation and reduction.

By determining magnetic vulnerability at a fairly coarse scale, we can identify locations of human occupation and middens. We do not have access to a dependable mag sus meter, but Jarrod Burks (who assisted teach at the course in 2013) has some excellent examples. Among which is the Wildcat site in Ohio.

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These villages are typically set out around a central open area or plaza, such as this reconstructed example at Sunwatch, Dayton, Ohio. Sunwatch Town, Dayton, Ohio (image: Jarrod Burks). At the Wildcat site, the magnetometer survey had actually located a variety of features and houses. The magnetic susceptibility survey helped, nevertheless, specify the main area of occupation and midden which surrounded the more open area.

Jarrod Burks' magnetic susceptibility survey results from the Wildcat site, Ohio. Red is high, blue is low. The method is therefore of great use in specifying locations of basic occupation instead of determining particular features.

Geophysical surveying is an applied branch of geophysics, which utilizes seismic, gravitational, magnetic, electrical and electro-magnetic physical methodologies at the Earth's surface to measure the physical properties of the subsurface - Geophysical Methods in Hillman Western Australia 2021. Geophysical surveying approaches typically measure these geophysical properties along with anomalies in order to assess various subsurface conditions such as the presence of groundwater, bedrock, minerals, oil and gas, geothermal resources, voids and cavities, and a lot more.