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John Waddell and his team from NUI Galway used techniques such as ground-probing radar and magnetic gradiometry, which measures the magnetic properties beneath the ground, as well as electrical tomography. For this, metal electrodes are placed into the ground and a current passed between them measuring its resistivity, which varies depending on what the substrata is composed of. A large number of such measurements taken in different directions and at various depths allowed them to use computer modeling to construct a three-dimensional image of the interior of the mound.