Projects - Geophysics
In partnership with Saltash Heritage, members of the Cornwall Archaeological Society have been involved with or
undertaken Geophysical surveys around Cornwall.
Geophysical survey’s carried out by CAS and Saltash Heritage are carried out using a
Magnetometer or/and a Resistivity Meter. There are other pieces of equipment that can
perform various functions within Geophysics available in the market, but these are not
used by CAS/Saltash Heritage.
In most systems, metal probes are inserted into the ground to obtain a reading of the
local electrical resistance. A variety of probe configurations are used, most having four
probes, often mounted on a rigid frame. Capacatively coupled systems that do not
require direct physical contact with the soil have also been developed. Archaeological
features can be mapped when they are of higher or lower resistivity than their
surroundings. A stone foundation might impede the flow of electricity, while the organic
deposits within a midden might conduct electricity more easily than surrounding soils.
Although generally used in archaeology for plan view mapping, resistance methods also
have a limited ability to discriminate depth and create vertical profiles.
Magnetometers used in geophysical survey may use a single sensor to measure the total magnetic field strength, or
may use two (sometimes more) spatially separated sensors to measure the gradient of the magnetic field (the difference
between the sensors). In most archaeological applications the latter (gradiometer) configuration is preferred because it
provides better resolution of small, near-surface phenomena. Magnetometers may also use a variety of different sensor
types. Proton precession magnetometers have largely been superseded by faster and more sensitive fluxgate and
cesium instruments. (http://en.wikipedia.org/wiki/Magnetic_survey_(archaeology))
The examination of the
properties using non-
invasive ground survey
techniques to reveal
features, sites and
Carwynnen Quoit March
Carwynnen Quoit July
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