Technology Explained

How GPS Works [MakeUseOf Explains]

Joel Lee 24-04-2013

how gps worksAs 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

What is the common point between nuclear power, the Internet The Internet & The World Wide Web Are Not the Same Thing [MakeUseOf Explains] The two terms "Internet" and "World Wide Web" have been used interchangeably ever since the Internet itself became a household "utility" as common as electricity or cable TV. People talk about "surfing the web" and... Read More , 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 to use gps

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 Sick Of Your GPS App’s Data Connection Flaking Out? Try 3 Updated Offline Maps [Android] Not long ago, Chris covered three of the best offline GPS apps available on Android. Since then, many other GPS apps released or received major updates. Do these newcomers compare favorably with those reviewed by... Read More ?


Think about what you use for GPS navigation. Whether it’s a dashboard mount from TomTom or the Maps app from Google How Does Google Maps Work? Google Maps is used by millions of people every day and you might be one of them, but how does it actually work and how does Google maintain its accuracy so well? Read More , 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 to use gps

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 to use gps

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

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 10 Proven and Tested Tips to Extend Battery Life on Android Suffering from poor battery life on Android? Follow these tips to get more juice out of your Android device's battery. Read More ? 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

Related topics: Geotagging, GPS.

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  1. Beh Han
    June 8, 2013 at 2:23 am

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

  2. Benny Teo
    May 10, 2013 at 12:24 pm

    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?

    • Kay Fritz
      May 11, 2013 at 4:15 pm

      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?

      • Benny Teo
        May 12, 2013 at 12:19 pm

        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.

        • Kay Fritz
          May 13, 2013 at 4:56 am

          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 ;-)

  3. jAy+
    May 9, 2013 at 10:20 am

    "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...

  4. Jean-Michel A
    April 30, 2013 at 4:56 pm

    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. Jean-Michel A
    April 30, 2013 at 4:56 pm

    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 ...

  6. Jean-Michel A
    April 30, 2013 at 4:56 pm

    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 ...

    • Kay Fritz
      May 7, 2013 at 6:26 pm

      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.

  7. mieszko200
    April 30, 2013 at 4:19 pm

    Thank you, it's very interesting.

  8. noname
    April 30, 2013 at 1:51 pm

    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.

    • Tina Sieber
      April 30, 2013 at 3:01 pm

      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.

    • John
      June 8, 2013 at 12:04 pm

      [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.

      • G.M.NELSON
        June 9, 2013 at 9:54 pm

        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).

  9. Rushinth John
    April 29, 2013 at 9:24 pm

    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.........

  10. Meidimi
    April 29, 2013 at 7:03 am

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

  11. Justin Winokur
    April 26, 2013 at 1:34 pm

    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

    • Joel Lee
      May 1, 2013 at 1:18 am

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

  12. techguyknows
    April 26, 2013 at 9:08 am

    Yes, a lot of Physics is involved!

  13. Kay
    April 26, 2013 at 5:05 am

    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.

  14. Erik
    April 25, 2013 at 5:54 pm

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

    Great GPS article btw!!

  15. Onaje Asheber
    April 25, 2013 at 4:18 pm

    Good info, yet easy read. Thanks a lot.

  16. Zhong J
    April 25, 2013 at 3:43 pm

    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.

  17. Chris Marcoe
    April 25, 2013 at 3:00 pm

    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.

  18. Steve Rudyk
    April 25, 2013 at 2:35 pm

    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?

    • Kay Fritz
      April 26, 2013 at 5:08 am

      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.)

      • Joel Lee
        May 1, 2013 at 1:16 am

        I believe your answer is correct. Thanks! :)

  19. Scott M
    April 25, 2013 at 10:35 am

    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.

  20. Rama moorthy
    April 25, 2013 at 8:33 am

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

    specially Russia using US satellite ...?

    • Joel Lee
      May 1, 2013 at 1:16 am

      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.

    • Cole Michael
      January 11, 2015 at 12:15 am

      I know this is an old, old comment, but Russia actually has its own GPS system, called GLONASS.

  21. Kirby
    April 25, 2013 at 3:07 am

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