ABINGDON ARCHAEOLOGICAL GEOPHYSICS

SAMPLE RESISTIVITY SURVEYS

Iron Age enclosure on chalk.

The ditch shows as a lighter colour indicating higher resistance than the surrounding soil. It may therefore contain rubble which has air voids which increase the electrical resistance of the ditch fill.

The ditch was also visible in magnetometry but that method could not detect the central building with its floor, which has stopped rainwater from percolating away, and the rubble surrounding it.

Each of the dots is a single reading - hence it is better to have a large enough area to see the picture properly.

Area of survey 100 x 80metres

PROFILE or PSEUDO-SECTION

Here is an example of a resistivity profile of a ditch cut into gravel with the section drawn from its excavation for comparison.