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Much of the image consists of blank locations now with little or no radar reaction. The "courtyard" wall is still showing strongly, however, and there are continuing suggestions of a difficult surface area in the SE corner. Time piece from 23 to 25ns. This last slice is now nearly all blank, but a few of the walls are still showing highly.

How deep are these slices? Regrettably, the software application I have access to makes estimating the depth a little tricky. If, however, the top 3 pieces 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 total.

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Fortunately 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 data (top left), the magnetometry (bottom left), the 1517ns time slice (top right) and the 1921ns time piece (bottom left).

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Magnetometry, as discussed above, is a passive strategy measuring local variations in magnetism against a localised absolutely no value. Magnetic vulnerability survey is an active strategy: it is a step of how magnetic a sample of sediment might be in the presence 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 fairly big.

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

By determining magnetic susceptibility at a relatively coarse scale, we can detect locations of human profession and middens. Sadly, we do not have access to a reliable mag sus meter, but Jarrod Burks (who helped teach at the course in 2013) has some exceptional examples. One of which is the Wildcat site in Ohio.

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These villages are often set out around a central open location or plaza, such as this reconstructed example at Sunwatch, Dayton, Ohio. Sunwatch Village, Dayton, Ohio (photo: Jarrod Burks). At the Wildcat website, the magnetometer survey had actually located a variety of features and homes. The magnetic vulnerability study helped, however, specify the main area of profession and midden which surrounded the more open area.

Jarrod Burks' magnetic vulnerability survey arises from the Wildcat site, Ohio. Red is high, blue is low. The strategy is for that reason of fantastic use in defining locations of general profession instead of identifying particular features.

Geophysical surveying is a used branch of geophysics, which utilizes seismic, gravitational, magnetic, electrical and electromagnetic physical methods at the Earth's surface area to measure the physical properties of the subsurface - Geophysical Surveys As Landscape Archaeology in Pearsall Oz 2023. Geophysical surveying approaches usually determine these geophysical homes in addition to abnormalities in order to evaluate different subsurface conditions such as the existence of groundwater, bedrock, minerals, oil and gas, geothermal resources, spaces and cavities, and far more.