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Indoor Nav System Uses Magnetic Fields

Last week RF Report covered the BAE Systems' NAVSOP, which provides “Navigation via Signals of Opportunity” using existing RF emitters. This week brought news of a navigation system that works by using the magnetic anomalies at a location rather than, or in addition to, RF signals at a location. 

The technology is described in the white paper Ambient magnetic field-based indoor location technology from IndoorAtlas Ltd. released this month. The white paper explains that 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 as animals use the Earth's magnetic field.” 

By using the magnetic sensors included in many modern smartphones for use as a compass, IndoorAtlas has developed a complete software toolbox for adding and managing floor plans and collecting data to create magnetic field maps and an API to use its location service for mobile applications. 

IndoorAtlas claims the system has an accuracy in modern buildings that ranges from 0.1 to 2 meters using only the magnetic sensors in the smartphone. No special equipment is needed to generate and use magnetic maps. The system has been tested in tunnels approximately 1,400 meters below ground in the Pyhäsalmi copper and zinc mine in central Finland. The white paper does not discuss what happens when the magnetic field changes--perhaps due to a passing subway train or other changes in the environment.