Geophysics

The geophysical survey has been successfully completed. The data has not been completely processed at this stage, but a rough interpretation has been given by Donna to aid us with the trial excavation.

Two types of geophysical survey were undertaken across the whole of the island. The first type uses an instrument called a fluxgate gradiometer (pictured above) and this measures magnetic effects caused by buried structures and objects. Therefore metal objects or areas of burning will be shown as high readings.

The second type uses a resisitivity meter, which passes an electric current through the ground and then measures the subsequent resistance met by this current. A wet area such as a drain or ditch would therefore show low resistance, whereas a wall or stonework would show as high resistance.

The following diagrams show some of the graphics produced by Donna so far. 

    
Position of the geophysics grid

Gradiometer image

Resistivity image

Interpretation of gradiometer