Indoor positioning via magnetic field measurement: This method of positioning makes use of the magnetic field of the earth. It takes advantage of the fact that modern buildings have a specific magnetic fingerprint, which results from the interaction of the earth’s magnetic field with the building materials used and the architectural features. The more steel used in the building, the better for this positioning solution. So what proves to be disturbing when positioning via radio signals is what makes positioning possible in this case. The steel is responsible for the characteristic interference of the earth’s magnetic field. Positioning with an accuracy of one to two meters should be possible with the help of the compass integrated in modern smartphones.
Pro:
- no infrastructure needed
Contra:
- Complex calibration
- Other systems have become more accurate
- Very few suppliers
These systems are also called Magnetic Indoor Local Positioning System (MILPS). There are also commercial systems in which an electromagnetic field is artificially generated. These enable very precise tracking of movements. They are not used for commercial location-based services, but are used in medical and military simulators. This paragraph therefore only refers to systems that use the Earth’s magnetic field.
Disadvantages of Magnetic Field Measurement
Disadvantages of the technology are that the magnetic field of the building has to be mapped in advance in a complex way and that the magnetic field of the earth is variable. The map of the magnetic field must therefore be updated regularly – in practice approximately every three months. To do this, the building must be completely run down and “scanned” manually. This makes the “installation” very complex, especially for large building complexes.
There are few companies that specialise in positioning via magnetic field as a stand-alone technology. But the technology can also be combined with WLAN or Beacon technology. Even the Finnish market leader IndoorAtlas now recommends combining the technology with beacons. However, this also leads to the system becoming less flexible. If a beacon is moved or is to change its location, either the beacon must be reconfigured or a new card must be installed.