If you’re of a certain age, I’m sure you can recall lots of times when you—regrettably—unfolded a paper map in your car, desperately scanned the thing in hopes of locating whatever place it was you were trying to get to, and then failed miserably to refold it again. Nowadays? You type or just say out loud where you want to go such as: “place where there is coffee” and magically your phone shows you more options than you were expecting…or perhaps, hoping.
GPS. The not-actually-magic, magical technology that beams signals from space and calculates with nanosecond precision so you don’t miss your exit…for coffee. Delicious, delicious coffee.
How does it all work? Well, grab yourself a mug and let’s find out what’s brewing. I’m Chris Rouman and I’m Nerd Adjacent.
What is it?
GPS, or Global Positioning System, was born out of the Cold War. In the early 1970s, the U.S. military wanted a navigation system that could guide submarines, ships, aircraft, and—of course— missiles anywhere on Earth with precision. The project, called NAVSTAR, was approved in 1973, and the first test satellites launched in 1978, laying the foundation for what was to come.
In 1983, after Korean Air Lines Flight 007 was tragically shot down when it strayed into Soviet airspace, President Reagan announced that once GPS was fully operational, it would be made available for civilian use. Through the late ’80s and early ’90s, more satellites went up, and by 1993 the system provided continuous global coverage.
At first, civilians only got a degraded signal, a security feature known as Selective Availability, that limited accuracy. But in 2000, President Clinton ordered it turned off, allowing everyday users to get much more accurate results. That decision set the stage for GPS to move from a Cold War tool to something that would guide cars, phones, and just about everything else… to, oh, I don’t know… coffee, for instance.
Before we get into the details of how this all works, here’s a fun fact: GPS in cars has been around way longer than most people think. Back in 1981, Honda experimented with an analog system with the awesome yet somewhat provocatively named Gyrocator. Mazda’s luxury Eunos Cosmo had the first built-in GPS in 1990. In 1992, Oldsmobile equipped Toronados—naturally—with TravTek, an information and traffic management system that used touchscreens and voice guidance, and included live help. Toyota and Alpine pushed integrated navigation mainstream in Japan, while GM’s GuideStar developed it in the U.S. in 1995. They were clunky and expensive, but they all offered a glimpse of what was coming.
How does it work?
So, how does this amazing tech help you find your next Venti Caramel Macchiato with almond milk and an extra shot of espresso? Well, let’s dig in and find out.
The GPS network is made up of at least 24 satellites, constantly orbiting the Earth. And it’s not just the U.S.—other countries have their own networks that function essentially the same way. Europe has Galileo, Russia has GLONASS, and China has BeiDou. Though these are completely different systems, most modern phones can use any of them.
Each satellite in the GPS constellation sends out a signal with the exact time it was transmitted. Your phone—or car or watch—receives that signal and notes how long it took to arrive. Because radio signals travel at the speed of light, a tiny delay means a measurable distance.
Your device does this with at least four satellites at once. With a bit of clever math—that I couldn’t possibly explain to you—it can triangulate your exact position in three dimensions: latitude, longitude, and altitude. It’s basically asking, “How far am I from Satellite A? What about B, C, and D?” And then drawing imaginary spheres around each one until the intersection lands…right where you’re standing. Presumably, in front of a coffee cart.
Now here’s where it gets even nerdier: GPS relies on atomic clocks onboard the satellites—super-precise timekeepers that are accurate to within billionths of a second. If the timing was off by even a millisecond, your location could be off by hundreds of miles. That’s how precise this system is.
And even nerdier yet: because the satellites are moving fast and are far from Earth’s gravity, they experience time slightly differently—a phenomenon explained by Einstein’s theory of relativity in which gravity plays a crucial role in how we perceive time. Because there’s less gravitational effect on GPS signals the further you get from earth, the speed of those signals can vary enough to throw things off. Engineers actually have to compensate for this so your phone doesn’t think you’re in the middle of the Pacific when you’re just trying to get to Trader Joe’s.
Why it matters?
GPS isn’t just about finding the nearest coffee shop so you can order your afternoon grande iced oat milk latte with two shots of blonde espresso, one pump of vanilla, and cinnamon on top. Light ice, please… It’s part of the invisible infrastructure that keeps modern life humming.
Shipping companies use it to track packages in real time. Airlines use it to navigate. Emergency responders use it to locate 911 callers and farmers use it for precision agriculture—planting seeds down to the centimeter.
And here’s one you might not expect—Wall Street runs on GPS. Not for directions, but for time. As I shared earlier, GPS signals come from atomic clocks on satellites, and that timing is what allows stock exchanges to timestamp trades. Every order, every quote, every millisecond decision in high-frequency trading has to be synchronized—across servers, cities, and continents. Without GPS, markets can’t stay in sync, and trades can’t be verified. If it sounds fragile, that’s because it is. There are entire contingency plans just to keep clocks running if the satellites go dark.
Conclusion
GPS is one of those technologies that quietly runs in the background of modern life. But it’s a masterpiece of engineering. And it’s proof that sometimes, the most incredible things are hiding in plain sight.
So, the next time you casually ask your phone where you can pick up a venti half-caf ristretto Americano Misto, made with three shots of espresso, steamed soy milk, one pump of hazelnut, one pump of toffee nut, a sprinkle of nutmeg, made at 190-degrees, remember this: A swarm of satellites is whizzing around the planet, broadcasting signals from space, using atomic clocks that account for general relativity—all so you can avoid left turns, and caffeine withdrawal.
What time is it anyway? Yeah, I could go for a coffee.