Earth Magnetic shift during Age of Exploration

What would be the impacts if a shift of the earth's magnetic field happened while people were still extremely reliant on compasses, how would this impede the progress of the west.
 
It's still a geological POD, that goes ASB unfortunately.

That really shouldn't be a hard and fast rule. We've had threads with storms and earthquakes as the POD and this is really not that different (besides the phenomenon being way less frequent). It really doesn't need to be in ASB.
 
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