If you have used a smartphone map or watched a delivery vehicle on a tracking app, you’ve used GPS. But GPS—the US Global Positioning System—is only one member of a broader family called global navigation satellite systems (GNSS). Four global satellite constellations circle Earth and guide aircraft, ships, cars, trucks and tourists. They also play a central role in modern warfare.
How satellites locate you
At its core, satellite navigation is about time. GNSS satellites carry extremely precise atomic clocks and continuously broadcast two key items: their exact orbital position and the precise time the signal was sent. Receivers on Earth—smartphones, cars, scooters, planes or ships—pick up these signals and calculate their position by comparing the time stamps from multiple satellites. Signals from four satellites give latitude, longitude and altitude, with a fourth used to correct timing errors.
GNSS is fast and highly accurate, and it’s deeply embedded in everyday life. But it has a hidden fragility. Signals are exceptionally weak when they reach Earth, so any radio noise near their frequencies—accidental or deliberate—can disrupt reception. “Signals from global navigation satellite systems are quite vulnerable,” says Dana Goward, president of the Resilient Navigation and Timing Foundation. He warns that awareness at leadership levels doesn’t always translate into actions to reduce risk.
Four global navigation powers
The first global navigation systems were developed during the Cold War. The US built GPS, the first to achieve full global coverage and the most widely used. The Soviet Union developed GLONASS. In the early 2000s the European Union created Galileo to reduce reliance on US infrastructure, and China developed BeiDou to lessen dependence on GPS and to provide regional enhancements over Asia.
The systems are similar and “dual-use,” serving civilian and military needs. “GPS, GLONASS, and Galileo all use very similar orbits, with a similar number of satellites at around 19,000 to 23,000 kilometers altitude,” says Malcolm Macdonald, professor of satellite engineering at the University of Strathclyde. BeiDou also uses higher-altitude orbits to bolster regional coverage. Most devices can use multiple constellations; many consumer devices pick signals from two or more systems. Japan and India operate regional systems that do not cover the entire planet.
GNSS in war
Armed forces increasingly rely on satellite navigation for logistics, mapping and operational planning. Navigation satellites guide weapons—including cruise missiles and precision bombs—and control drones. That dependence makes GNSS a target.
Electronic warfare tactics such as jamming and spoofing are common in conflicts like the Russia–Ukraine war. Jamming interferes with signal reception; spoofing deceives receivers by feeding false location or timing data. Spoofing is harder to execute than jamming but can be more disruptive: it can make a navigation system report speeds and locations that are wildly incorrect, or hide the real position of ships or vehicles. Thomas Withington, an electronic warfare analyst at the UK’s Royal United Services Institute, describes spoofing that reports an aircraft as departing one airport while it is actually in a car outside another city.
Real-world consequences have included attempts to mask vessel movements and incidents where injected errors pushed ships into another country’s territorial waters, enabling boarding and detention. Macdonald cites such manipulations in sensitive regions like the Strait of Hormuz.
Resilience and responses
Some countries—Russia and China—have domestic, terrestrial systems that can complement and back up GNSS. Goward notes this gives them an advantage over Western countries, which lack equivalent ground-based alternatives. There is no single technology that fully neutralizes GNSS disruption; multiple approaches are being explored, including terrestrial timing and navigation networks and inertial navigation systems.
In wartime, one of the most expedient responses is practical: locate the jammer and destroy it. Military planners also work on hardening receivers, using multi-constellation signals, and integrating alternate navigation methods, but the ubiquity and convenience of satellite navigation mean GNSS will remain both indispensable and a contested asset.
Edited by: Zulfikar Abbany