The indoor Atlas uses Earth's magnetic field. From where does this magnetic field originate?

IndoorAtlas' location technology is partly inspired by evidence that animals use the Earth’s magnetic field

not only for orientation detection but also for true navigation (Boles et al. 2003, Wlitschko et al. 1972,

Maugh et al. 1982, Mouritsen et al. 2004, Mora et al. 2004). Some animals, such as spiny lobsters, are not

only able to detect the direction of the Earth's magnetic field they can even sense their true position relative to

their destination. This means these particular animals are able to derive positional information from local cues

that arise from the local anomalies of the Earth's magnetic field.

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Modern buildings with reinforced concrete and steel structures have unique, spatially-varying ambient

magnetic fields that can be used for positioning, in much the same way (albeit on a much smaller spatial

scale) as animals use the Earth's magnetic field. In principle, a non-uniform ambient magnetic field

produces different magnetic observations, depending on the path taken through it.

In IndoorAtlas' location technology, anomalies

(fluctuations) of ambient magnetic fields are

utilized in indoor positioning. This has been

facilitated by modern smartphones and the rapid

development of sensor technology. The image

on the right shows an example of indoor

magnetic fields present in modern buildings

(Time Warner Center, New York, US, June 2012).

Explanation:

their crystal patterns have been disrupted by stress