For the first time, researchers have used real-time data from around 40 million mobile phones to map conditions in the ionosphere - a region of the upper atmosphere in which some of the air molecules are ionized. Such crowdsourced signals could improve satellite navigation, especially in swathes of the world where data are otherwise scarce, including Africa, South America and South Asia.
Phone data could reduce GPS errors by 10-20% in some areas, and more in underserved regions, estimates Ningbo Wang, an atmospheric physicist at the Aerospace Information Research Institute of the Chinese Academy of Sciences in Beijing.
When the air is partly ionized, freely moving electrons slightly slow down the radio signals travelling to Earth from GPS and other navigation satellites. This can affect the nanosecond-precision timing.
It's an amazing data set, says Anthea Coster, an atmospheric physicist at the Massachusetts Institute of Technology in Cambridge. It fills in the map a lot, in areas where we desperately need more information.
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