53Fenwick, 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.

Regarding the dating of the monument, the authors write, "The possibility that [the Ditched Pit Circle] is quite early in the monument sequence at Tara may be reflected in the fact that, according to the geophysical image, it does not appear to have cut or truncated any monuments (though the strength of its 'signature' might effectively obliterate or mask lesser features). It is quite possible that its incorporation of Duma na nGiall [the Mound of the Hostages] is deliberate, and therefore that the ditched pit circle post-dates the passage tomb. Supporting this suggestion is the fact that the pit circle at Newgrange, which compares quite well with the Tara specimen, also encloses an undifferentiated passage tomb and so it is possible that this type of couplet is a recurring motif."