Archaeological Survey   Resistivity is an active technique that
uses probes to introduce an electrical current into the soil,
measuring the resistance of the soil to the passage of the
current (see Clark 2000; Heimmer and De Vore 1995; Somers
2006).  In a typical archaeological application, a mobile probe
array includes one probe to introduce a current into the ground
and a second probe to take a voltage measurement.  A pair of
stationary probes located at some distance from the mobile probe
array provide a return path for the current probe and reference
voltage from the voltmeter (Somers 2006:113). The resistance of
the soil between the two mobile probes is calculated by taking
the ratio of voltage (measured) to current (known).  This is
converted to a measurement of resistivity by factoring in the
distance between the mobile probes (see Somers 2006:113).
Resistivity Image of Strawtown Enclosure  The electrical
resistance of a soil is related to its “porosity, permeability,
saturation, and chemical nature o