Magnetometer
Magnetometer surveys are the most frequently used geophysical technique in Ireland, allowing rapid mapping of magnetic anomalies contained within the sub-soil. Many archaeological features gain a strong magnetic signature from burning and heating processes; other features such as the fill of ditches and pits gain a natural magnetism over time which can also be detected.
Magnetometer (or Magnetic Gradiometer) surveys are undertaken by hand-held machines which are carried across the survey area in a grid system. Each instrument contains sensors which measure the difference between the magnetic content of the earth and the local soil within the survey area, producing a map of the underlying archaeological content.
Surveys are usually conducted on a 1m line spacing with readings taken every 0.25m along the line; this sample resolution is often increased within research situations or where small features such as pits, post-holes or graves are thought to be located.
Magnetometer surveys are ideal for detecting:
- Hearths
- Kilns
- Burnt Mounds of Stone
- Ditches
- Pits
- Other Burnt or Fired remains
