So don't do a calibration ever, simple ! It's your choice to calibrate on a pier , knowing darn well that it is steel reinforced in some way, just like people who calibrate on their steel reinforced driveways . Do it right and or don't do it at all ! Most experienced pilots who started on platforms from day one of compass controls have done it with no issues ! Once done , unless you change location drastically you are good to go ! My H out of the box, hovered erratically, did a CC and been rock steady since! It's your choice!