Most people encounter global satellite navigation every day — when they check a map on their phone, track a delivery, or use in-car directions. These services rely on GNSS, the family of Global Navigation Satellite Systems. GPS is the best-known example, but it is one of four global constellations that provide positioning, navigation and precise timing.
How GNSS figures location
GNSS determines position by measuring time. Each satellite carries an extremely precise atomic clock and continuously broadcasts two pieces of information: its exact orbital position and the precise time the signal was sent. A receiver on the ground picks up signals from multiple satellites and compares timestamps. With signals from at least four satellites, the receiver computes latitude, longitude and altitude and corrects for clock errors. The system is fast and highly accurate, which is why it is embedded in so many civilian and commercial applications. But the signals arriving from space are very weak, which creates an important vulnerability: they can be drowned out or manipulated by radio interference.
The four global constellations
The first GNSS networks were developed during the Cold War. The United States created GPS, the first to provide full global coverage and the dominant system for civilian use. The Soviet Union built GLONASS. In the 2000s the European Union deployed Galileo to reduce reliance on foreign infrastructure. China’s BeiDou is the newest global system, designed to ensure Chinese military and civilian autonomy; it also uses additional orbits to strengthen regional coverage across Asia. Many devices today can receive signals from multiple constellations for redundancy. Japan and India operate regional systems that do not provide global reach.
GNSS and modern warfare
Military forces depend heavily on satellite navigation for logistics, mapping, targeting and controlling unmanned systems. That dependence makes GNSS signals and the infrastructure that supports them attractive targets. In recent conflicts, including the war in Ukraine, combatants have used electronic attacks against navigation signals. Jamming overwhelms receivers with noise and denies service; spoofing sends counterfeit signals that make receivers compute incorrect positions or times. Spoofing is more technically demanding than jamming but can be used to conceal movements or deliberately mislead adversaries — for example, causing navigation systems to think a vehicle is somewhere it is not.
Vulnerabilities and mitigations
Because GNSS signals are weak, they are susceptible to accidental interference and deliberate disruption. Some countries have developed domestic terrestrial backup systems to reduce reliance on satellite signals; Russia and China have invested in such complementary networks, while Europe and the United States have been slower to deploy nationwide terrestrial backups. There is no single technological fix that eliminates GNSS risk. Common mitigations include using multiple satellite constellations, integrating inertial navigation and other sensors, hardening receivers against spoofing, and developing resilient timing sources. In active conflicts, locating and disabling jammers is often the most immediate countermeasure. Research and operational changes continue to improve resilience, but the global reliance on vulnerable satellite signals remains a strategic weakness.