Mapping the ionosphere with millions of phones

The ionosphere is a layer of weakly ionized plasma bathed in Earth’s geomagnetic field extending about 50–1,500 kilometres above Earth1. The ionospheric total electron content varies in response to Earth’s space environment, interfering with Global Satellite Navigation System (GNSS) signals, resulting in one of the largest sources of error for position, navigation and timing services2. Networks of high-quality ground-based GNSS stations provide maps of ionospheric total electron content to correct these errors, but large spatiotemporal gaps in data from these stations mean that these maps may contain errors3. Here we demonstrate that a distributed network of noisy sensors—in the form of millions of Android phones—can fill in many of these gaps and double the measurement coverage, providing an accurate picture of the ionosphere in areas of the world underserved by conventional infrastructure. Using smartphone measurements, we resolve features such as plasma bubbles over India and South America, solar-storm-enhanced density over North America and a mid-latitude ionospheric trough over Europe. We also show that the resulting ionosphere maps can improve location accuracy, which is our primary aim. This work demonstrates the potential of using a large distributed network of smartphones as a powerful scientific instrument for monitoring Earth.

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Although measurements from individual mobile phones are noisier than those from conventional monitoring stations, we have shown that millions of phones in concert yield valuable measurements of ionospheric TEC. Other recent work has shown that phone accelerometers can detect earthquakes to provide early warning33 and that phone barometers can improve weather forecasting34. Building on these examples, our work continues to illuminate the potential for mobile phone sensors as a powerful tool to improve the scientific understanding of our planet.

Source: Mapping the ionosphere with millions of phones | Nature

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