Here’s How GPS Actually Works

4 minute read
Updated: | Originally published: ;

From smartphones to action cameras, all manner of devices pack GPS these days. And while you might think it’s a newer innovation, GPS has actually been around since the 1970s, when it was developed by the U.S. Department of Defense. Between then and now, relatively little has changed with how the Global Positioning System works. So it’s probably time you figured out what makes it tick — because while you may be on the move, GPS isn’t going anywhere.

According to Cesar Palacios, who works with GPS device company Garmin on its personal navigation devices and automotive GPS units, there are three fundamental segments to GPS: control stations, satellites, and users’ devices. “[GPS] benefits everyone from pilots to fishermen, making their lives a little bit easier,” he says.

The control segment consists of 30 locations around the world that track, control and communicate with GPS satellites. The master control station, located at Schriever Air Force Base in Colorado Springs, is where the system is managed, making sure the satellites are operating correctly and efficiently.

The next segment of the system, orbiting 12,550 miles above Earth, are 32 GPS satellites. Between maintenance and other concerns, those satellites may not all be active at the same time. But they broadcast a lot of information: Almanac data, which relates the health and general whereabouts of all GPS satellites, ephemeris data, which offers more precise information about a single satellite, and pseudorandom code, which identifies the transmitting satellite.

Top 10 Tech Product Designs of 2014

Nest Acquired by Google in Jan. 2014, Nest Labs wants to turn your home into a smart device. The home automation system includes Internet-connected smoke detectors and thermostats, which have screens and chic, round designs — a huge design boost for devices that haven't really changed in recent decades. Aya Brackett—Nest
DJI Inspire 1 The latest DJI quadcopter retains the simple style that's made their drones so popular, but adds 4K video capability — and the ability to transmit the HD video wirelessly to an on-the-ground devices. A new ground-facing camera also allows Inspire 1 to fly steadily to keep the video footage clean.
DJI Inspire 1 The latest DJI quadcopter retains the simple style that's made their drones so popular, but adds 4K video capability — and the ability to transmit the HD video wirelessly to an on-the-ground devices. A new ground-facing camera also allows Inspire 1 to fly steadily to keep the video footage clean.DJI
iPhone 6 and 6 Plus Bigger is better, or so the critics cried, calling for Apple to make a supersized phone. That was before Apple quieted them with the release of the iPhone 6 Plus in September, the company’s largest iPhone ever. With an alluring 5.5-inch display that makes it feel something like a portable iPad, the phone is is a challenge to Samsung’s larger models. Along with a powerful 8-megapixel camera and longer battery life, the phone is more a statement than an answer.Apple
Osmo Tangram
Osmo Tangram Tired of seeing your kids staring at screens like zombies? This iPad game brings virtual play to life. A reflector equipped with artificial intelligence snaps over your iPad's camera and can sense when objects are moving (or being drawn) on a pad in front of it. Osmo comes with three games, all of which promote creativity and—because it’s best played in groups—social intelligence. The best way to understand how Osmo works is by watching the video of kids who have never played with the device before testing it out for the first time.Osmo
Tesla 2014 Model S Tesla 2014 Model S has been praised both for its luxury feel and high-tech interior. The electric car offers instantaneous acceleration from a stop, a function very few other cars on the market provide. Tesla
Jawbone's Up3 wristband
Jawbone's UP3 Wristband Depending on your view, Jawbone is on the road to making us all super fit athletes or brutally efficient cyborgs who operate by data alone. How many minutes of REM sleep did I get last night? What’s the difference between my heart rate while resting and during a workout? How hydrated am I? How many calories did I burn on my last run? Jawbone UP3 answers all those questions better than any other Jawbone did before. The $179 wearable fits on your wrist and comes in black and silver.Jawbone
Square Stand The iPad holder and credit card reader launched last year with the goal of transforming an iPad into a point-of-sale. The sleek, white stand also offers an enhanced credit card reader, and can be adapted to include a cash register.Square
Nerf Rebelle Rapid Red Blaster
Nerf Rebelle Rapid Red Blaster Last year, Nerf decided to even the battlefield and create a new line of guns, arrows and crossbows specifically for girls. The resulting Nerf Rebelle line takes a cue from the success of The Hunger Games: The box is covered with tweens styled like that series' hero, Katniss Everdeen.Hasbro
Oculus Rift Crescent Bay The latest Oculus Rift prototype, Crescent Bay, marks one step further before the commercial release of the virtual reality handset. Crescent Bay features upgrades like 360-degree head tracking, a lighter weight, and high-quality audio. Lucky participants in the demos recalled the mind-boggling immersion in the scenes they were watching. The consumer version, Oculus Rift, is expected to launch as early as April 2015.
Oculus Rift Crescent Bay The latest Oculus Rift prototype, Crescent Bay, marks one step further before the commercial release of the virtual reality handset. Crescent Bay features upgrades like 360-degree head tracking, a lighter weight, and high-quality audio. Lucky participants in the demos recalled the mind-boggling immersion in the scenes they were watching. The consumer version, Oculus Rift, is expected to launch as early as April 2015.Oculus VR
Qualcomm WiPower Sick of tangled phone charging cables? Qualcomm WiPower allows you to power up your phone without plugging it in — a function that, to most people, is basically magic. The wireless charging pad eliminates the fuss of power chords, while also allowing you to turn everyday furniture like tables and chairs into charging surfaces.Qualcomm

And timing is an important thing when it comes to these far-flung pieces of technology. Per Einstein’s theory of relativity, time moves more slowly in areas where gravitational pull is greater, so the clocks on GPS satellites actually tick a fraction of a second faster than clocks on Earth. GPS satellite and receiver companies counteract this effect by programming their devices to compensate for it.

The third segment of the system are the consumer devices themselves — your smartphone, your car’s onboard computer, or even your fitness tracker. To have your position located using one of these gadgets, your GPS device must be able to get a signal from at least three of the system’s satellites. Using a process called trilateration, these orbiting bodies are able to tell where you are. For most consumer devices, the results are accurate to within 10 meters.

“The reason why you can’t get that pinpoint, exact accuracy is that we’re consumer-grade,” says Palacios. “The government agencies are the only ones who have that pinpoint, precise, encrypted code GPS, to know the exact location.”

Still, there is a way to get more information out of your GPS, says Palacios. “If you have four or more satellites, that’s when you’ll get 3-D positioning, which is latitude, longitude and altitude, as well.” Assuming, of course, your device can display this extra data.

Of course, GPS only works outdoors with line-of-sight with the orbiting satellites. But there are several emerging technologies used by companies like Apple, Home Depot, and Philips to cover the indoors in a GPS-like system. In the future, expect GPS devices to proliferate as it miniaturizes. As the tech gets smaller, you’ll start finding them in things like smartwatches, fitness bands and even dog collars.

“Even if you’re in a stadium or trying to remember where you parked, with wearables, you can just drop a digital breadcrumb and be able to go back to that location later,” says Palacios.

Correction: The original version of this article misstated the definitions of ephemeris and almanac data. Ephemeris data is precise data from one specific satellite, almanac data is less precise information about the entire GPS satellite fleet.

More Must-Reads from TIME

Contact us at letters@time.com