If you've ever used a map on your smartphone or tracked a delivery vehicle on an app, you've already used GPS.

What many people don't know is that GPS—the US Global Positioning System—is just one part of a larger family known as Global Navigation Satellite Systems. Satellite (GNSS).

Four global satellite systems orbit the Earth. They guide airplanes, ships, cars, and trucks, or tourists looking for a place to eat. But they also play a central role in warfare.

How do satellites tell us where we are?

Essentially, satellite navigation is a matter of timing. GNSS satellites carry extremely precise atomic clocks and constantly transmit two key pieces of information: our exact position in orbit and the exact time the signal was sent.

Meanwhile, on Earth, receivers—our phones, cars, an airplane, or a ship—pick up these signals to determine our exact location.

To do this, they use signals from at least four satellites, which allows them to calculate latitude, longitude, and altitude, as well as correct for any timing errors.

GNSS technology is very accurate and fast. It is deeply integrated into everyday life. But it also has a little-seen fragility.

“The signals from global navigation satellite systems are quite vulnerable,” Dana Goward, president of the Resilient Navigation and Timing Foundation in the United States, explained to DW.

“They are extremely weak, which means that any radio interference near their frequency, accidental or intentional, can affect reception,” he noted.

Four global navigation powers: the US, Russia, Europe, and China

The first two global navigation systems were developed in the 1970s, during the Cold War between the United States and the then Soviet Union.

The United States developed GPS, which became the first satellite navigation network with complete global coverage. And it is today the most widely used system in the world.

At the same time, the Soviet Union developed GLONASS.

Later, in the early 2000s,the European Union decided that relying exclusively on GPS made it too dependent on US strategic infrastructure, and began developing Galileo.

The Chinese BeiDou system is the most recent of the four. As in Europe, Chinese military planners sought to reduce their dependence on US GPS.

All four systems are very similar and “dual-use”: they are designed for both civilian and military purposes.

“GPS, GLONASS, and Galileo use very similar orbits, with a similar number of satellites at altitudes between 19,000 and 23,000 kilometers,” explained Malcolm Macdonald, professor of satellite engineering at the University of Strathclyde in Glasgow. “BeiDou complements [its system] with higher-altitude orbits to strengthen regional coverage in Asia.”

Each system can send signals to any point on the planet at any time, even to devices as small as a wristwatch.

“Most devices use several [satellite] constellations. It depends on the equipment: for example, my smartwatch can use GPS and GLONASS, and I can configure it to use one or the other, or both.”

Japan and India also operate similar systems, but they do not cover the entire planet; instead, they offer regional services.

How Navigation Systems Are Used in Warfare

Increasingly, armed forces rely on satellite navigation for logistics, mapping, and operational planning.

It is also used to guide weapons, including cruise missiles and so-called smart bombs.

Armies also use these systems to control drones. But this has made satellite targets. In conflicts like the war between Russia and Ukraine, both sides have resorted to electronic warfare, using techniques such as jamming and spoofing. These are used to interfere with signals or deceive GPS-based systems on the ground. Spoofing is more difficult than jamming, but it offers the possibility of confusing the adversary. “Your navigation system might indicate that you are traveling at 400 knots and leaving Helsinki Airport, when in reality you are in a car traveling at 120 kilometers per hour on the outskirts of Berlin,” explained Thomas Withington, an electronic warfare analyst at the Royal United Services Institute in the United Kingdom. Goward warned that this could pose a greater threat to Europe and the United States than to Russia and China, since these countries have “their own ground-based systems that complement and support GNSS, while the West does not.”

And what is most frustrating, according to Withington, is that there is no single technology capable of effectively neutralizing GNSS disruptions.

Technological alternatives are being developed, but for now, in a wartime context, one of the most “expeditious” solutions remains “locating the jammer and destroying it.”