Google uses millions of smartphones to map the earth's ionosphere and to improve GPS
Google uses millions of smartphones to map the earth's ionosphere and to improve GPS
For the first time, researchers used real -time data of around 40 million mobile phones to map conditions in the ionosphere - an area of the upper atmosphere in which some air molecules are ionized. Such crowdsourcet signals could improve satellite navigation, especially in regions of the world where data is otherwise rare, such as Africa, South America and South Asia.The feasibility study of the Google team was published on November 13th in the journal Nature 1 .
"It is an amazing data record," says Anthea Coster, atmospheric physicist at the Massachusetts Institute of Technology in Cambridge. "He completes the card considerably in areas where we urgently need more information."
The data of mobile phones could reduce GPS errors in some areas by 10–20% and even more in under-supplied regions, estimates Ningbo Wang, atmospheric physicist at the Aerospace Information Research Institute of the Chinese Academy of Sciences in Beijing. Even with adjustments, the disorder due to the ionosphere remains a challenge, especially during solar storms that trigger uneven conditions in the ionosphere. "The results presented are really impressive."
dual ligaments
In the event of partial ionization of the air, the freely movable electrons slow down easily and influence the radio signals that get to Earth from GPS and other navigation satellites. This can affect the temporal synchronization at the nanosecond level, which is used by the satellite navigation devices to determine their locations. This has potentially serious effects on aircraft landings and autonomous vehicles.
real -time maps of the density of these electrons are often used to correct fluctuations in the ionosphere. Engineers create the cards using data from floor -based reception stations that can recognize the arrival times of two different frequencies of radio waves received by the same satellite. Electrons in the ionosphere slow low -frequency waves more than high -frequency, for example a nanosecond. This difference provides information about the density of the electrons through which the wave has gone through on the way to a recipient.
Without these corrections, the GPS would be about 5 meters inaccurate and during solar storms by dozens of meters if invited particles increase the electron density from the sun. But many regions of the world are missing the floor -based reception stations to create these cards.
noise backdrop
Although not all navigation devices can work with several frequencies, modern phones often do this. According to Brian Williams, computer scientist at Google in Mountain View, California, and co -author of the study, telephone sensors were not previously regarded as practical to map the ionosphere. This is because the data of mobile phones are much more intoxicating than the specifically developed scientific reception devices, especially because they only receive signals intermittently and the radio waves in urban areas are reflected on nearby buildings.
The Google team was partially successful thanks to the large number of data obtained. "When large quantities are combined, the noises are compensated for and you still get a clear signal," says Williams. "It is as if there is a scientific surveillance station in every city in which phones are."
Anyone who has an Android phone and allows Google to collect sensor data to improve location accuracy was able to contribute to the study. However, the data has been aggregated so that individual devices cannot be identified, the company explains.
Williams explains that it is already being worked on using this technology to improve location accuracy for Android users. But the data should also be useful for scientific studies in the upper atmosphere of the earth. The card has already revealed bubbles in ionized gas, known as plasma, about South America that were not previously observed in detail.
To really use science, Google has to publish the data, says Coster, which works on the Madrigal database, a community resource for geospatial data that combines ionospheric dates of thousands of ground stations. A spokesman for Google informed the Nature news team that the data behind the study is published together with the article, but there are currently no plans to provide fresh data in real time.
researchers are working on using other smartphones in other ways. Google's Android Erdbiebenwarn system in 2020 showed how acceleration sensors in the smartphones of people recognize earthquakes and warn others that could still be affected. Apple users can access an app that uses a similar technology.
So far, scientists have regarded telephones as end users of navigation services, says Wang. This reversal to use telephone data as input data is "new territory," he says. "This study marks an exciting change."
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Smith, J. et al. Nature 635, 365–369 (2024).