Don Johnson conducting the electrical resistivity survey.  The device Don is using has several probes that are pushed into the ground.  Two probes are also placed into the ground in an area outside of the grid being tested.  These are connected to the wire that is behind him.  With each stop, the resistometer measures the difference in resistance at that point compared to the points off the grid.  The resistometer measures resistance at two depths, one at about a half meter and one at about one meter below the surface.