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Much of the image consists of blank locations now with little or no radar reaction. The "yard" wall is still revealing strongly, nevertheless, and there are continuing ideas of a tough surface in the SE corner. Time slice from 23 to 25ns. This last piece is now nearly all blank, however a few of the walls are still revealing strongly.

How deep are these slices? Unfortunately, the software I have access to makes estimating the depth a little challenging. If, however, the top three slices represent the ploughsoil, which is most likely about 30cm think, I would guess that each slice is about 10cm and we are just getting down about 80cm in overall.

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Thankfully for us, the majority of the sites we have an interest in lie simply listed below the plough zone, so it'll do! How does this compare to the other approaches? Contrast of the Earth Resistance data (top left), the magnetometry (bottom left), the 1517ns time piece (top right) and the 1921ns time slice (bottom left).

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Magnetometry, as discussed above, is a passive technique determining regional variations in magnetism against a localised zero value. Magnetic vulnerability study is an active method: it is a measure of how magnetic a sample of sediment might be in the presence of a magnetic field. Just how much soil is evaluated depends on the diameter of the test coil: it can be very little or it can be reasonably big.

The sensing unit in this case is extremely little and samples a tiny sample of soil. The Bartington magnetic vulnerability meter with a large "field coil" in usage at Verulamium during the course in 2013. Top soil will be magnetically improved compared to subsoils merely due to natural oxidation and reduction.

By measuring magnetic susceptibility at a reasonably coarse scale, we can detect areas of human occupation and middens. We do not have access to a trustworthy mag sus meter, however Jarrod Burks (who helped teach at the course in 2013) has some exceptional examples. One of which is the Wildcat website in Ohio.

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These towns are often laid out around a main open area or plaza, such as this rebuilt example at Sunwatch, Dayton, Ohio. The magnetic susceptibility survey assisted, nevertheless, specify the main area of profession and midden which surrounded the more open area.

Jarrod Burks' magnetic susceptibility survey arises from the Wildcat website, Ohio. Red is high, blue is low. The technique is therefore of excellent use in defining locations of general profession rather than determining specific features.

Geophysical surveying is a used branch of geophysics, which uses seismic, gravitational, magnetic, electrical and electromagnetic physical methodologies at the Earth's surface to measure the physical properties of the subsurface - Geophysical Surveys For Planning & More in Hazelmere Aus 2020. Geophysical surveying methods generally measure these geophysical properties together with abnormalities in order to evaluate different subsurface conditions such as the existence of groundwater, bedrock, minerals, oil and gas, geothermal resources, voids and cavities, and much more.