With reservations --simply because I don't know their details-- I'll say that this is nothing new at all and it could be the makings of another case of patent a

With reservations --simply because I don't know their details-- I'll say that this is nothing new at all and it could be the makings of another case of patent abuse. Local changes to the magnetic field have been used for quite some time for purposes such as oil exploration. I remember talking to an old geologist/oil man about twenty years ago as he went about locating candidate areas to explore based on these fluctuations. He explained that they'd use magnetometers to map out underground "cracks", deposits and other features. To go from that from generating local location data by overlaying a map of some sort (whether it is a building or something else) is nothing less than trivial. If you have any experience sailing you may have also witnessed the effect of large sunken metallic objects on the compass. Again, you could "navigate" by these effects "Hey we must be passing over the SS-Sunken Ship". Gotta love patents.