52Condit Tom. "Beneath the Ground at Tara." Archaeology Ireland, vol. 13, no. 1, 1999, p. 29.

The fluxgate gradiometer, which measures anomalies in the earth's natural magnetic field caused by underground disturbances, was used by Joe Fenwick to carry out the survey. This device can help to identify pits, trenches and other features which are no longer visible on the surface. The Ditched Pit Circle, technically a hengiform ceremonial enclosure, is analogous to timber circles and enclosures, such as at the Ballynahatty Giant's Ring, and at Brú na Bóine.

There is as yet no definitive evidence that the pits were intended to support timber uprights, but "...the exceptional clarity of the signature invites comparison with the growing corpus of palisaded enclosures and pit and timber circles from Ireland and Britain." (Fenwick, Joe, and Conor Newman. "Geomagnetic survey on the Hill of Tara, Co. Meath, 1998-9." Discovery Programme Reports: 6: Project Results, 2002, pp. 11-15.)