This post is also available in:
עברית (Hebrew)
GPS has become the backbone of modern navigation, powering everything from smartphones and connected vehicles to emergency services and autonomous systems. But satellite signals are far from perfect. In dense cities, tunnels, underground spaces and areas where signals are blocked or degraded, GPS accuracy can drop dramatically or disappear altogether. That creates challenges for applications that depend on continuous and reliable positioning.
Researchers have developed a hybrid positioning system that tackles this problem by combining conventional satellite navigation with an unexpected source of location data: underground fiber-optic cables. The new approach, called Joint DAS and GNSS (JDG), fuses GPS information with data collected through Distributed Acoustic Sensing (DAS) to maintain accurate tracking even when satellite signals become unreliable.
Unlike GPS, DAS does not rely on satellites. Instead, it turns existing fiber-optic communication cables into long, continuous vibration sensors. As people or vehicles move near a buried cable, they generate tiny vibrations that slightly alter the light traveling through the optical fiber. According to TechXplore, specialized equipment detects these minute changes and converts them into movement information, effectively allowing the cable to act as a sensor extending for kilometers.
To test the concept, researchers conducted a field experiment in southern England. Volunteers walked alongside a roadside fiber-optic cable while their GPS positions and the cable’s vibration data were recorded simultaneously. Both data streams were then processed by a deep-learning model trained to combine the two information sources. When GPS signals became weak, noisy or unavailable, the system continued estimating the person’s location using the vibration data from the fiber-optic cable.
According to the research team, the hybrid system consistently outperformed GPS-only positioning and other prediction methods, maintaining accurate tracking even during complete GPS outages. The researchers also found that the approach remained effective on lower-power devices that collect location updates less frequently, suggesting it could be adapted for smartphones, Internet of Things (IoT) devices and other battery-powered systems.
Although the project focuses on civilian positioning, the technology could also have significant defense and homeland security applications. Reliable navigation is critical for military personnel, autonomous vehicles and emergency responders operating in environments where GPS signals are degraded, obstructed or intentionally jammed. Combining satellite navigation with infrastructure-based sensing could provide an additional layer of resilience, helping maintain situational awareness when conventional positioning systems become unreliable.
The researchers believe hybrid systems such as JDG could support future smart transportation networks, autonomous navigation and emergency response by making location services less dependent on uninterrupted satellite reception. As positioning technologies evolve, integrating multiple sensing methods may prove to be a practical way to overcome one of GPS’ biggest limitations.
The research was published here.
