resistivity survey

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A kind of geophysical survey used to locate buried features by mapping differences in the way that soils conduct an electric current. Using a resistivity meter a controlled electric current is passed through the soil between four electrodes. One pair of electrodes carries the current while the second pair measures the voltage passed through the ground; the resistance (in ohms) is determined and recorded. In general, fine densely packed damp silty material offers little resistance to current passed through it but stony deposits and those with abundant spaces in the matrix are highly resistant. Different arrays of electrodes allow different depths to be targeted, and by moving the electrodes in a systematic pattern a detailed map of subsurface soil conditions can be built up. Rubble‐filled ditches and pits, walls, courtyard surfaces, and roads are the easiest features to identify with resistivity. Limitations in the technique include the problem of filtering out natural from anthropogenic anomalies, and ensuring that the survey is conducted under fairly uniform soil conditions (neither too wet nor too dry).

Subjects: Archaeology.

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