- Phone-based maps outperform the traditional Klobuchar ionospheric model globally
- Underserved regions like Africa benefit from enhanced ionosphere data
- Geomagnetic storms are tracked with high precision using smartphone networks
Mapping the ionosphere is critical for improving the accuracy of navigation systems, but existing methods face significant limitations. While ground-based GNSS stations provide detailed maps of ionospheric total electron content (TEC), their coverage is uneven, leaving large gaps in underserved regions.
Now, researchers from Google Research, Mountain View, CA, USA, have demonstrated an innovative solution utilizing millions of Android smartphones as a distributed network of sensors in a study published in Nature.
Despite being less precise than traditional instruments, these devices effectively double the measurement coverage, offering accurate ionosphere data and addressing longstanding infrastructure disparities.
The Ionosphere’s influence on navigation
The ionosphere, a layer of ionized plasma extending from 50 to 1,500 km above Earth, significantly impacts Global Navigation Satellite System (GNSS) signals by introducing positioning errors. However, traditional ground-based GNSS stations, while precise, suffer from limited spatial coverage and leave underserved regions vulnerable to inaccuracies.
The research from Google Research capitalizes on the billions of smartphones equipped with dual-frequency GNSS receivers to address coverage gaps. Unlike conventional GNSS stations, smartphones are mobile, widely distributed, and capable of capturing vast amounts of data.
By aggregating and averaging measurements from millions of devices, researchers achieved accuracy comparable to dedicated monitoring stations, even resolving phenomena like solar storms and plasma density structures.
Android’s GNSS API facilitated the collection of satellite signal data, such as travel times and frequencies, which were then used to estimate the ionospheric total electron content (TEC).
The study showed that while individual phone measurements are noisier than those from monitoring stations, their collective data provided robust and reliable results.
Comparisons showed the phone-based TEC model outperformed existing methods like the Klobuchar model, widely used in mobile phones.
Using data from Android phones, the researchers doubled the measurement coverage of the ionosphere compared to traditional methods, and were able to map plasma bubbles over India and South America and storm-enhanced density over North America during a geomagnetic storm in May 2024.
They also observed mid-latitude troughs over Europe and equatorial anomalies - a phenomena previously inaccessible due to sparse station coverage.
Notably, regions like India, South America, and Africa, often underserved by traditional monitoring networks, benefited significantly from this approach, which produced real-time, high-resolution TEC maps.
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