Those are "structural welds" and they need not be pretty.
Fred I don't think those are vias, it looks to be welding splatter. In the likely advent that they are vias then its bound to be a very complex algorithm for reducing ground noise by confusing it.
In Rick's defense the calibration gas was probably used to produce those welds. Rick I've heard Methane works well as a shielding gas, try that next time you weld. Improvement guaranteed!
Credit where credit is due, it produces a range of numbers that vary with RPM (and sometimes without).
