Electrical resistivity

Hunter Geophysics undertaking an electrical resisitvity survey for La Trobe University.

Electrical resistivity

Electrical resistivity surveys are capable of detecting variations in the soils electrical resistivity, which usually reflects an increase or decrease in soil moisture which, in turn, is reflective of buried archaeology.

Resistivity surveys are generally slower than other techniques, although due to its method of direct-contact measurement (i.e. by using steel electrodes which are inserted into the ground), resistivity is not prone to atmospheric and weather interference as electrical conductivity surveys are.

Electrical resistivity surveys are best used on clay soils, where ground-penetrating radar may not be as effective.

Electrical resistivity tomography (ERT)

ERT surveys involve measuring the electrical resistivity of the soil at different depths across a survey area. The data is then collated into a data ‘cube’, showing the variation of resistivity across the site at different depths. In this manner, three-dimensional models of buried archaeological features can be created.

An electrical resistivity survey of a 4x30 metre area showing a high-resistance anomaly, possibly a buried gravel path (in white) and the soil immediately surrounding the path (in black), which is a low-resistance feature and is believed to be a wetter soil due to drainage from the path.

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