12Waddell, John, Joe Fenwick, and K. J. Barton. Rathcroghan: Archaeological and Geophysical Survey in a Ritual Landscape. Dublin: Wordwell, 2009. 174.
In another statement, Waddell refers to "A bewildering complexity of overlapping linear, arcuate and annular anomalies occur in the surface layers beneath the summit..." (168).
The magnetic gradiometry image on the page (color added) has revealed pits, ditches and palisade trenches. The great mound is in the center, ans seems to have various structures entombed within. "On the east it is approached by a trapezoidal avenue in which two burial mounds are visible. Immediately to the north a northern enclosure has its own eastern avenue. All these features are encircled by a very large ditched enclosure 360m in diameter." (Waddell, John. Archaeology and Celtic Myth: An Exploration. Dublin, Ireland: Four Courts, 2014. 17.)
As would be expected with an emerging technology, the ability of archaeologists to accurately interpret the meaning of geophysical measurements continues to evolve. In the humorous feature "Spoil Heap: A 'Dictionary' of Irish Archaeology," the word "Geophysics" is defined as a "method of survey based on spiritualism where archaeologists gather around a table placed over a suspected underground structure and contact the spirit world in an effort to determine the shape of the monument below..." (Archaeology Ireland, 10:1 (Spring, 1996) 36.)