Ann: Assays Confirm Major Copper Discovery at Big One Deposit, page-41

Drill Hole electro magnetics.

They send an EM probe down the drill hole to conduct geophysical tests in additional dimension to what they can get at surface. So picture electromagnetic pulses going sideways (and all around) from within the drill hole as opposed to just down from the surface.

The tech has been getting some great results in recent times identifying potential sulphide targets for further drilling. I would expect our geos will be using it to firstly get clear insight into the shape of the deposit - where it's dipping and secondly for further deposition at depth and also to see if there's a mirror deposits.