How GPS Works [MakeUseOf Explains]

How GPS Works Intro   How GPS Works [MakeUseOf Explains]As an avid gamer, I’m surprised by the correlation between GPS-like features in modern video games and the proliferation of GPS technology in mundane life. When I was a kid, paper maps and cartography were still common; if you got lost, you suffered through it and found your way to your destination. Nowadays, we’ve got the wonders of GPS to guide us there and back again.

I’m only 24 so I don’t mean to sound like the pre-GPS era was a “golden age” or anything like that. I appreciate the convenience of GPS and it has saved my butt on more than a dozen occasions. But like a lot of technology, we tend to take it for granted. I know I do.

What is GPS? Do you know how GPS works? What’s the secret behind the near-pinpoint accuracy that it offers? Keep reading to learn about the impressive thought that went into building this magnificent navigational system.

how gps works device   How GPS Works [MakeUseOf Explains]

What is the common point between nuclear power, the Internet, and GPS? They all started as projects meant to bolster the US’s technological edge over the rest of the world. Specifically, the technological edge of their military. The Internet would allow fast communication over long distances; nuclear power could be both destructive and energy generative; and GPS meant ease of navigation for military forces through foreign terrain.

The GPS, which stands for global positioning system, is actually a network of 27 man-made satellites that orbit around Earth. Out of those 27 satellites, 24 are currently in use and the remaining three are there as failsafes in case one of the 24 malfunctions. Based on the arrangement of these satellites, at least four of these satellites are visible in the sky at any given time.

how gps works satellite   How GPS Works [MakeUseOf Explains]

In tandem with the orbiting satellites, there are five monitoring stations on the Earth’s surface: the master station (in Colorado) and four unmanned stations placed in faraway locations that are as close to the equator as possible (Hawaii is one of those locations). These unmanned stations collect data from the satellites and forward to the master station, which interprets and makes adjustments before relaying the proper data back to the GPS satellites.

Though this system was originally intended for military use, the US opened up the system in 1983 for civilian use which is why we can use those satellites today to find our nearest Starbucks at the snap of our fingers.

Okay, so we have this global system of satellites and stations that are constantly shifting around in the Earth’s atmosphere and relaying data back and forth. How do our mobile devices and car trackers tap into the system to figure out where exactly we are? And if there are so many satellites floating around up there, why does your GPS signal sometimes fail?

Think about what you use for GPS navigation. Whether it’s a dashboard mount from TomTom or the Maps app from Google, the idea is the same: your device is a GPS receiver. In other words, your device receives data from the GPS satellites overhead. What sort of data? Simply put, each satellite tells your device the distance between you and that satellite.

At this point, you may be a little confused because you’d think you need more than distance from an object to pinpoint your exact location. And you’d be right! Using the distance from each satellite, your GPS device can use a technique called trileration to find where you are.

how gps works trilateration 1   How GPS Works [MakeUseOf Explains]

Imagine you’re lost out in the wilderness. If you called your friend in Philadelphia and he magically knew exactly how far away from him you were, he’d tell you that you’re 400 miles from Philadelphia. Knowing that isn’t enough, though, because that distance from a single point could mean any point along the circle of a 400-mile radius around that point.

how gps works trilateration 2   How GPS Works [MakeUseOf Explains]

So you call a second friend in New York City and he says you’re 300 miles away. Now you have two circles of distance and every point along those circles is a potential place where you could be at this moment. As you can see, the two circles intersect in two spots: based on the distance data, you know you are at either one of these spots.

how gps works trilateration 3   How GPS Works [MakeUseOf Explains]

And if you called a third friend and he told you that you were 200 miles from Newark, you’d have three circles that intersect in one location. That’s where you are.

This same technique is used by the GPS where each satellite can be viewed as one of your friends from the example above. But since satellites work in 3D space, you’d have to imagine the intersection of spheres instead of circles. Combine that distance data with the fact that you must be standing on the surface of the Earth (which acts as the 4th sphere) and it’s pretty easy to find where you are.

For accurate GPS data, most devices try connecting to at least four satellites. This is also why it sometimes takes a long time for your device to update GPS locations. It’s also why you sometimes don’t have a signal: you may be connected to one or two satellites, but that isn’t enough.

Of course, there’s a lot more math and science behind how GPS works. For example, compensating for the signal delay between satellites and receivers (radio waves only move so fast). Ever wondered why GPS kills your phone’s battery? It’s because your phone needs to constantly correct errors in calculation.

Hopefully you learned a bit about the GPS and how it works. I actually didn’t know how it all worked until I did my research for this article and the idea behind it is both fascinating and clever. If you still don’t understand it, perhaps I didn’t explain it well enough; in that case, I urge you to ask questions in the comments for clarification.

Image Credits: GPS Network Via Shutterstock, GPS Phone Via Shutterstock, GPS Satellite Via Shutterstock

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32 Comments -

7 votes

Kirby

I think you did a pretty good job explaining the article for anyone to grasp the idea behind this tech.

5 votes

Rama moorthy

Is whole world uses the same satellites launched by US ..? some having own satellites ….?

specially Russia using US satellite …?

0 votes

Joel Lee

The GPS system is controlled by the US, but they opened it up for the world to use due to the potential for civilian applications. So yes, I believe Russian GPS still uses US satellites.

5 votes

Scott M

A great explanation for anyone curious of how a service like this is able to offer such precision and accuracy in directional navigation.I believe that it is one of the most important advances in technology from the Military that has been made available for the average citizen.I just turned 60 and its mind boggling that I am able to this in my car.Its like one of those world of tomorrow pieces that I used to read in Popular Science magazine.

5 votes

Steve Rudyk

Great ino- Very helpful. Now that I understand the basic theory, I have even more questions. Who or what updates the names of streets, highways and roads. I’m amazed how GPS recites names of highways and even some dirt roads. How is thata data base kept current? Can users provide feedback, e.g. re pronunciation?

6 votes

Kay Fritz

Actually there are different databases and that doesn´t have anything to do with GPS. The databases are provided by companies or even open source communities. Your GPS system in your car/phone just makes use of both and combines them. GPS tells you the exact position, and the database tells you what is at that point (streets, shops, buildings, etc.)

1 votes

Joel Lee

I believe your answer is correct. Thanks! :)

5 votes

Chris Marcoe

the technology in my hand-held Magellan I have now is way better than the technology I used while in Iraq 10 years ago. I’ve never had my car or hand-held tell me I was off the coast of Chile. but wile in Iraq, My Plugger (Its what we called the big, bulky GPSs we had) told me that.

5 votes

Zhong J

This kind of locator can be found on apps such as iphones, if you have internet access then you can identify your location through google maps where it’ll exactly be updated of where you are.

5 votes

Onaje Asheber

Good info, yet easy read. Thanks a lot.

0 votes

Erik

oops, posted that to the wrong article! Please disregard…

Great GPS article btw!!

0 votes

Kay

Very nice – in order to complete that you now have to explain what a SUPL server does, and maybe the difference between SUPL and SUPL2.

0 votes

techguyknows

Yes, a lot of Physics is involved!

6 votes

Justin Winokur

I think this article is actually a bit misleading. For example:
” For example, compensating for the signal delay between satellites and receivers (radio waves only move so fast).”

This is not something that need to be compensated for. This IS the key to the system. It is that exact delay that lets the receiver know how far it is from the satellite. However, the receiver needs to compensate for its own clock’s delay. Furthermore, you talk about needing 4 receivers but not why. The picture in 2D shows why you need 3 circles. It similar in 3D, but you really need 5 to account for the internal clock delay. However, you can get by with 4 by assuming you’re on or near the earth’s surface.

These details, especially about the signal delay, are not minor and should not be swept under the rug. They are the key to the technology

0 votes

Joel Lee

Thanks for expounding with those details. I wasn’t as clear as I could’ve been!

0 votes

Meidimi

Thanks, explained it really well. any noob will understand it.

5 votes

Rushinth John

Wow…really loved this article…thought I knew how it worked but I was wrong…felt the article would be long but it was short anyways the explanation was good………

5 votes

noname

The sat’s are beyond Earth’s atmosphere – that’s one of the major factors keeping them from falling out of orbit. Still, a good read, thx.

5 votes

Tina Sieber

Earth’s atmosphere has several layers. The outermost layer (Exosphere) is up to 800km from Earth’s surface.

The International Space Station orbits Earth at around 330 – 410km, around the same altitude as some weather and navsats. Other satellites, including stationary ones are thousands of kilometers from Earth.

In other words, satellites are found both inside and beyond Earth’s atmosphere.

0 votes

John

[quote]The sat’s are beyond Earth’s atmosphere – that’s one of the major factors keeping them from falling out of orbit. Still, a good read, thx.[/quote]

Actually, things that orbit the earth are not floating or suspended due to being free of the influence of gravity or atmosphere––they are constantly falling toward the earth. It’s just that the orbiting object’s forward speed/inertia are set to match the rate of fall. So the speed necessary to maintain orbit is determined by the radius of the orbit, and the farther out the object is orbiting the faster it must travel to maintain the orbit. GPS satellites orbit at a distance that provides a speed that matches the earth’s rotation, movement relative to the earth’s surface is minimal, causing them to appear suspended from our perspective.

0 votes

G.M.NELSON

Actually the GPS satellites are NOT in geo-stationary (apparently unmoving) orbits, this type of orbit is for satellites that must not appear to move and is at a specific altitude above the equator and used for communications relay (e.g. your TV satellite). The GPS satellites are in a complex series of orbits at varying angles so that from any point on the surface 4 or more satellites are line-of-sight visible (mathematically) at all times (although the calculations do not take into account obstructions).

1 votes

mieszko200

Thank you, it’s very interesting.

0 votes

Jean-Michel A

I have a few question on a cell phone/tablet does GPS need connection to a service provider in order words must I have my SIM card in the phone to use? what is the difference between DATUM GLONASS and all the other names attached to GPS last but not least It is my understanding that the GLONASS which was championed by RUSSIA is the most reliable? lots and lots of questions thank you …

5 votes

Kay Fritz

I only will answer the first question – in the current smartphones/tablets you don´t need a data connection, BUT than it could take a few minutes until your device finds enough satelites to determine your position. With a data connection you will make use of SUPL or SUPL2 and than it usually takes not more than 30sec to get your correct position.

With GLONASS you´re so much in SUPL2, that you only want to know, if you´re doing standardisation, so rather not ask.

0 votes

Jean-Michel A

I have a few question on a cell phone/tablet does GPS need connection to a service provider in order words must I have my SIM card in the phone to use? what is the difference between DATUM GLONASS and all the other names attached to GPS last but not least It is my understanding that the GLONASS which was championed by RUSSIA is the most reliable? lots and lots of questions thank you …

0 votes

Jean-Michel A

I have a few question on a cell phone/tablet does GPS need connection to a service provider in order words must I have my SIM card in the phone to use? what is the difference between DATUM GLONASS and all the other names attached to GPS last but not least It is my understanding that the GLONASS which was championed by RUSSIA is the most reliable? lots and lots of questions thank you …

0 votes

jAy+

“Global Positioning System”
I have a rather solid understanding regarding this ‘feed back’ based “harmony”.
Satellites acquire and maintain There Own position from our devices , (at times) just as we attain position. :]

IS THIS the method behind programs (such as google earth) ability to generate vehicle traffic data??
Oh so Curious this is…
;}

5 votes

Benny Teo

Q: If the mobile is a GPS receiver, why do some phones (eg Google Nexus) still require data connection before being able to pinpoint your location? What does the Nokia Lumia phones have that is able to do this without a data connection?

5 votes

Kay Fritz

I think I already explained that earlier, but here you go again.

Current smartphones/tablets make use of AGPS (AssistedGPS) which comes in the form of a data connection to a SUPL/SUPL2 server that supports to find your position faster.

What makes you think the Nokia Lumia doesn´t make use of that? Either you were very lucky or if it is based on your data traffic counter than it propably doesn´t count against it, but still was using it. I hope that helps?

0 votes

Benny Teo

Well with data roaming off & wifi off when Im overseas, I was able to track my position. I guess as you mentioned, it probably doesnt count against it.
Thanks!

0 votes

Kay Fritz

With roaming and wifi off that shouldn´t be possible – you should never get a data connection, that would be huge problem. So my guess is, you were very lucky.

And believe me, you can be very unlucky with GPS – I stood once in a parking lot in Las Vegas in the sun at noon for about 15 minutes ;-)

0 votes

Beh Han

Great info! Very helpful for me.
Finally I can understand how GPS works :)