“We eavesdropped on the signal, and then we designed sophisticated algorithms to pinpoint our location, and we showed that it works with great accuracy, and even though Starlink wasn’t designed for navigation purposes, we showed that it was possible to learn parts of the system well enough to use it for navigation,” said Zak Kassas, associate professor of mechanical and aerospace engineering at UCI and director of CARMEN.
The discovery of this method has left the researchers hopeful that it could serve as a viable alternative to GPS at some point. Kassas says that as the Starlink constellation grows, the accuracy of these methods will also increase.
“The important catch here is that we are not ‘listening’ in on what is being sent over these satellites. We learned the signals just well enough to harness them for navigation purposes,” Kassas said.
GPS signals rely on satellites in much higher orbits than low-Earth orbiting (LEO) satellites like Starlinks. Consequently, LEO satellites have stronger signals that are less susceptible to interference and potentially less vulnerable to attacks due to the novelty of this method compared to the well-understood systems powering GPS.
With signals from six satellites, the researchers pinpointed a location within 8 meters of accuracy here on Earth. The researchers did not require any assistance from SpaceX, nor did they have any access to the data any satellites were transmitting, only information relating to the location and trajectory of the satellites. The research team was based out of the University of California-Irvine (UCI) in partnership with the Center for Automated Vehicles Research with Multimodal Assured Navigation (CARMEN), a multi-institution transportation center housed at The Ohio State University.
The team set up an antenna on campus at UCI, using the algorithm they developed to pinpoint its location. They could locate the antenna within ~7.7 meters, compared to GPS’ accuracy of between 0.3 and 5 meters generally. Previously, using other satellites, the team has been able to pinpoint locations within ~23 meters. Working with the United States Air Force, they could locate high-altitude aircraft within 5 meters using land-based cellular signals.