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

How deep are these pieces? The software application I have access to makes approximating the depth a little difficult. If, nevertheless, the top 3 slices represent the ploughsoil, which is probably about 30cm think, I would guess that each slice is about 10cm and we are only getting down about 80cm in overall.

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Thankfully for us, the majority of the sites we are interested in lie just below the plough zone, so it'll do! How does this compare to the other techniques? Comparison of the Earth Resistance information (leading left), the magnetometry (bottom left), the 1517ns time slice (leading right) and the 1921ns time slice (bottom left).

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Magnetometry, as talked about above, is a passive strategy measuring regional variations in magnetism against a localised zero value. Magnetic susceptibility survey is an active strategy: it is a measure of how magnetic a sample of sediment might be in the presence of an electromagnetic field. How much soil is evaluated depends on the size of the test coil: it can be very small or it can be reasonably big.

The sensor in this case is really small and samples a small sample of soil. The Bartington magnetic vulnerability meter with a large "field coil" in usage at Verulamium throughout the course in 2013. Leading soil will be magnetically enhanced compared to subsoils merely due to natural oxidation and reduction.

By measuring magnetic susceptibility at a fairly coarse scale, we can spot areas of human profession and middens. Sadly, we do not have access to a trustworthy mag sus meter, but Jarrod Burks (who assisted teach at the course in 2013) has some outstanding examples. One of which is the Wildcat website in Ohio.

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These towns are frequently laid out around a central open location or plaza, such as this reconstructed example at Sunwatch, Dayton, Ohio. The magnetic vulnerability study helped, however, define the primary location of occupation and midden which surrounded the more open location.

Jarrod Burks' magnetic susceptibility study arises from the Wildcat website, Ohio. Red is high, blue is low. The technique is therefore of excellent use in specifying locations of basic occupation rather than identifying particular features.

Geophysical surveying is a used branch of geophysics, which uses seismic, gravitational, magnetic, electrical and electro-magnetic physical approaches at the Earth's surface to determine the physical residential or commercial properties of the subsurface - Geophysical Survey In Archaeology in Gwelup WA 2022. Geophysical surveying methods normally measure these geophysical residential or commercial properties together with anomalies in order to examine numerous subsurface conditions such as the existence of groundwater, bedrock, minerals, oil and gas, geothermal resources, voids and cavities, and much more.