What happens if you have a property boundary that gets offset by a fault moving - do you own the moved land or do you own own the land that has moved into your area on a map and lose the land that moved out?
Just kidding. It is an interesting question though. I suppose the legal answer would vary by locality. It seems that any definitions derived by GPS, which normally would seem to be most accurate, would be too inflexible in this circumstance. It would seem hardly fair to get sued because you left your house in their new front yard.