The British School at Rome

Resistivity survey is based on the ability of sub-surface materials to conduct an electrical current passed through them. All materials will allow the passing of an electrical current through them to a greater or lesser extent. There are extreme cases of conductive and non-conductive material, but differences in the structural and chemical make-up of soils mean that there are varying degrees of resistance to an electrical current.

Resistivity survey at Calatia (Photo: L.Pett)

This technique is particularly suitable for locating buried structures, such as walls and floor surfaces, as it allows a high degree of precision and resolution. The technique has been successfully used by the BSR for surveying villa sites (see Forum Novum) and Roman towns (see Portus and Falerii Novi).
As a survey method, whilst it allows a relatively large area to be covered in a short amount of time, it is, however, more time dependent than magnetometry. The BSR therefore recommends that the technique is used together with magnetometry survey to investigate a smaller area in more detail, or, that a survey is more limited in its size.
The array used by the BSR utilises a Geoscan Research RM15 Resistance Meter in a twin electrode probe formation, however surveys can also be undertaken using other arrays, such as Wenner and dipole-dipole.

Further Reading

Clark, A. 1996: Seeing beneath the soil: Prospecting methods in Archaeology: Second edition, London, Batsford

Gaffney, C and Gater, J., 2003, Revealing the buried past: Geophysics for archaeologists, Stroud: Tempus.

Gaffney, C., Gater, J., Ovendon, S. 1991: The use of geophysical survey techniques in archaeological evaluations. Institute of Field Archaeologists Technical Paper No.9.

to top

Geophysical Survey

Survey Techniques