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. Resistivity 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. (http://en.wikipedia.org/wiki/Electrical_resistance_survey_(archaeology)) Magnetometers 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 Proton precession magnetometers have largely been superseded by faster and more sensitive fluxgate and cesium instruments.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))

Geophysics The examination of the Earth's physical properties using non- invasive ground survey techniques to reveal buried archaeological features, sites and landscapes.

Survey’s involving CAS Carwynnen Quoit March 2009 Bosporthennis 2009 Carwynnen Quoit July 2010