Starlink blocks access to its GPS alternative ahead of SpaceX IPO

"In 2021, a team led by Zak Kassas, director of the Autonomous Systems Perception, Intelligence, and Navigation (ASPIN) Laboratory at The Ohio State University, showed how electronically eavesdropping on signals from six Starlink satellites could pinpoint locations on Earth to within 8 meters of accuracy-although that required 13 minutes of tracking rather than delivering instantaneous results."

"Such opportunistic eavesdropping is challenging, because Starlink is consistently optimizing for its primary satellite Internet service by turning beams on and off, or sometimes switching beams as the fast-moving satellites talk to many different users, Kassas explained. That creates unpredictable jumps in the signal timing estimates that the researchers rely upon to calculate positioning data."

"To tackle those challenges, Kassas and his colleagues use Doppler measurements of signal frequency changes that reflect satellite motions relative to the receiver, along with software algorithms to correct for timing errors. They have also deployed phased array antennas-capable of communicating with just one or two satellites at a time-in combination with low-gain, omni-directional antennas that can capture signals from nearly 10 satellites at a time."

"By 2025, the researchers had shown how to harness signals from an average of three Starlink satellites to deliver positioning results to within 2 meters of accuracy in just 20 seconds. But this general eavesdropping strategy is not just limited to Starlink's thousands of satellites-they have also exploited satellite signals from Orbcomm, Iridium, Starlink, OneWeb, NOAA, and the dedicated PNT constellation, Xona."

In 2021, researchers demonstrated that passively receiving signals from six Starlink satellites could locate positions on Earth within 8 meters, requiring about 13 minutes of tracking. Opportunistic eavesdropping is difficult because satellite internet service changes beam patterns and timing estimates unpredictably as satellites switch beams and serve many users. The approach uses Doppler measurements of frequency shifts caused by satellite motion relative to the receiver, combined with software algorithms that correct timing errors. Phased array antennas communicate with one or two satellites at a time, while low-gain omni-directional antennas capture signals from nearly 10 satellites simultaneously. By 2025, average use of three Starlink satellites achieved about 2 meters accuracy in roughly 20 seconds. The method also applies to signals from Orbcomm, Iridium, OneWeb, NOAA, and Xona, and has been tested on ground vehicles, balloons, and drones, including improved ship navigation using Starlink and OneWeb together.

Read at Ars Technica