The wonderful invention that is GPS (global positioning system) tracks your location by using satellites. The problem is that you must be outside to have clear access. . . what about when you’re all turned around inside the big city mall? Well now there are some researchers testing an IPS (indoor positioning system) using the magnetic fields of Earth to figure your position.
. . .any phone with a built in magnetometer will be able to produce these maps, which are accurate down to 10 centimeters.