Resistivity survey can be
particularly useful for locating structural remains associated with
building footings. In addition, the technique can locate former ditches
and pits. Surveys are possible over grass, crops and open soil. The
majority of our surveys are now carried out using the latest Geoscan
RM85 cart mounted system allowing data collection densities similar to
standard magnetometer surveys.
The electrical resistance or resistivity of the soil depends upon the moisture content and distribution within the soil. Buried features such as walls can affect the moisture distribution and are usually more moisture resistant than other features such as the infill of a ditch. A stone wall will generally give a high resistance response and the moisture retentive content of a ditch can give a low resistance response.
Image of resistivity survey of Pillerton Priors Roman villa
Archaeological Surveys believe resistivity is currently underused due to generally higher cost per area when compared to magnetometry. However, the technique often provides similar information to magnetometry and frequently can be superior. The rapid data collection possible using cart based systems has resulted in more competitive costs for resistivity. The efficacy of any geophysical technique shoule be carefully considered on a site by site basis.