How Does GPS Work? GPS for Dummies –

about everyone understands that GPS uses satellites to pinpoint our status on earth. Whether you have a GPS unit or use a smartphone with GPS, understanding some of the principles behind how it works will help you feel confident when using or purchasing one. In this guide, I ‘ll demystify GPS using plain speech and then share some tips to get the most out of your GPS .In this Guide:

  • How Does Your GPS Work?
  • How A GPS Figures Out Where You Are
  • Getting More Accuracy From a GPS
  • Practical GPS Tips For Better Performance

GPS is Satellite Based Radio

Gps 3 SatelliteThe backbone of GPS is a series of satellites orbiting the earth. Here’s what the latest (GPS 3) satellites look like. Each one is basically a refrigerator with solar panels that costs $547 million dollars. Photo USAF When people say “ GPS ” they are referring to a system of navigation that pinpoints your situation on earth by using signals from radio satellites orbiting the earth. All you need to get your position is a GPS liquidator. Almost all smartphones have a GPS receiver built-in today. A GPS receiver does not transmit any signals, all it does is receive GPS datum beamed to earth from GPS satellites. If you ca n’t receive the GPS signals, you ca n’t get your position. Each GPS whole, careless of size, has a modest chipset and GPS antenna. GPS signals are received via the antenna and then sent to the chipset, which is the workhorse, decoding the satellite signals, performing multiple calculations based on the GPS information, and then spitting out a placement .Gps ChipToday you can buy a sophisticated GPS chipset for $10. Some devices, such as smartphones, can have the GPS/location technology built into the main device chipset. In general it’s not something you have to worry about, but occasionally your GPS might update the software for the chipset.

GPS is Really GNSS

The acronym GPS ( Global Positioning System ) is generally used synonymously with the more accurate acronym GNSS (global navigation satellite system). Why ? Because GPS was the first global satellite placement system, started in 1993 by the uracil Government ( now run by Space Force ). GPS was in the first place conceived by the Department of Defense for the military, but since its launch in 1993, has been leveraged by users cosmopolitan.

Since then other countries have gotten in on the dissemble, launching their own GNSS systems. And for each GNSS system, new satellites are being launched all the meter, and the technology in them continues to improve. Although each GNSS has it ‘s own particulars, they all exercise on the lapp fundamental principles that I ‘ll cover in this guide .

System Country Satellites Coverage
GPS USA 33 global
GLONASS Russia 27 global
Galileo EU 30 global
QZSS Japan 7 Asia
IRNSS India 7 Asia
BeiDou China 27 global

Eos Tools Pro March 2017Today many phones and handheld units can receive signals from multiple GNSS satellites and use them all to determine your position. Photo EOS It should besides be noted that these are the GNSS systems that are publicly available. other countries ( I ‘m looking at you UK ) have been rumored to have their own GNSS systems that are only available for military practice. And commercial satellites such as Elon Musk ‘s StarLink will be able to augment current positioning systems ( from an accuracy of 300cm to 70cm ) and possibly even work on its own as a GNSS. Want to know what GNSS systems that your Android call can receive ? Try the GPSTest app. For iPhones, you have to go to the specification page on Apple .

The GPS Signal

Getting Gpx FixThink of your GPS as a radio that can pick up GPS signals, just like an AM radio can pick up radio stations. Except that with a GPS, the signal is traveling about 20,000 km from space. If you ‘re familiar with AM or FM radio, you know that stations have a radio frequency. For exemplar, in Southern California, you can tune your car radio into KPCC public radio on FM 89.3, or 1070 KNX on AM. GPS signals are similar, but rather of AM or FM, they are on something called the L-Band, which roughly lies below the band used for AM radio. Why the L-Band ? Because this hardening of radio frequencies can penetrate clouds, daze, rain, storms, and vegetation with minimal noise ( more on that belated ). The idea is that it works anywhere. The actual GPS signal is a serial of “ ons ” and “ offs ” in a specific format that gives your GPS recipient information about the satellite, the time the signal was sent, and the satellite ‘s position. Your GPS unit not alone receives this information, but besides measures how long it takes the signal travel from the satellite to your receiver, at the speed of light, to determine the distance between you and the satellite. This measurement of elapsed sign travel time is key to getting accurate measurements. In decree for a GPS to work correctly, the times must be synchronized across all the placement signals. To put the importance of correct meter in context, a 0.001 second error equates to a 300km inaccuracy. so each GPS satellite has an nuclear clock, the most stable and accurate time reference ever developed ( using the element Rubidium most of the time ), and it uses that clock to broadcast its clock. nuclear clocks in satellites are expensive ( $ 50-100k ) and big, but today you can get one for $ 1500 that fits in your pocket. Your GPS receiver does not have an atomic clock, but quite a quartz glass one. In the conclusion, the GPS time does n’t matter much. An accurate atomic time signal is pulled from a GPS sign to synchronize ( more in the adjacent section ) .

How GPS Determines Your Position

At a minimum, your GPS receiver needs three satellite signals ( aka “ fixes ” ) to determine your position, which is called trilateration .Gps Circle AWith one signal, you can be anywhere within the surface of the sphere.Gps Circle BWith two signals, you can be anywhere on the blue line where the two spheres intersect.Gps Circle CWith three spheres, there are two intersection points. This is called trilateration. One fix will be on the Earth’s surface, the other one will be in space. The GPS chipset will discard the one in space and give back the position of the one on the surface. Garmin also calls this a 2-D position.Gps Circle DAdding a fourth satellite will give you one point of intersection, eliminating the need to discard the point in space. It will also allow the GPS to calculate elevation. This is sometimes referred to as your 3-D position. This fourth signal is also used to sync time. Most GNSS systems strive to have their satellite orbits distributed so that at least four satellites are always visible from any point on the Earth at any time for this reason. Remember the theory of relativity ? Because fourth dimension moves faster for objects with less gravity, like GPS satellites, their clocks get 38 microseconds faster than earth clocks every day. That equates to about 6 miles of accuracy. The GPS system has been programmed to address this, and having a fourth satellite fixate helps eliminate time errors .

Do More Satellites Increase Accuracy?

No and yes. theoretically, for a three-d position, you merely need 4 signals / spheres. They will all intersect at one target. Adding more spheres will not make that one point anymore of one bespeak. In practice, a GPS chipset will be performing multiple trilateration calculations using unlike sets of signals, and then using statistical analysis to narrow down that set of positions to a more accurate single position. So having more satellites to choose from, assuming the GPS chipset can handle them, will help .

How Accurate is GPS?

Gpsmap 65 Elevation AccuracyI can regularly pinpoint myself to within 6 feet of accuracy with a modern multi-band GPS unit like the Garmin GPSMAP 65s. Phones like the Garmin Pixel 5 can leverage the same technology to get this type of precision as well. According to the official US Government web site for GPS, most consumer GPS units are accurate to a 16 feet radius. On newer multi-band GPS units, you can get a 6 foot accuracy regularly. early multi-GNSS units normally fall around 9-16 ft. now how this figure is actually generated is character of the secret sauce in the GPS unit and you have to take that figure with a grain of salt. There are factors that I ‘ll talk about following that can degrade your accuracy, but these are dear general figures. I ‘m assuming everyone wants as accurate of a GPS fixate as possible, but it helps to put GPS accuracy into context. The US Parks Service recommends that trails be built with a minimal width of 4ft. If you ‘re hiking and your GPS is giving you 6-16ft of accuracy, that should be more than adequate to help you voyage. It should besides be adequate to record your track reasonably accurately. It ‘s probably not enough to guide a self-driving cable car without plunging it off a cliff. And just adenine authoritative as accuracy is dependability. You want a position accuracy figure that stays ceaseless as you move through canyons, tree cover, and buildings. Newer engineering can help keep a reliable fix as you move around. I ‘ll talk about that concisely a well .Mt Langley Survey MarkerWant to really see how accurate your GPS fix is? Before you head out, see if there are any survey benchmarks on your route by searching the USGS database. The database will give you latitude, longitude, and elevation. Compare that to what the GPS is telling you and you can evaluate your real-world accuracy.

What Causes GPS Inaccuracy?

In an ideal worldly concern, your GPS unit of measurement would receive four perfective GPS signals with no hindrance, read all the information, and calculate a precise stead. But in the real number world, there are factors that can degrade the GPS bespeak as it travels the 12,550 miles from space to earth. The effect of GPS signal noise is bad or incomplete GPS datum. A modern GPS chipset will evaluate the quality of the GPS bespeak and throw out those that are not good. More archaic GPS units will just give you a less accurate situation. here are the main culprits that can degrade your GPS accuracy .Space Weather“Space Weather” refers to the amount of solar activity affecting the electrical fields in the Ionosphere (between 80 and 600km above earth). When there are solar flares and other solar phenomena, the GPS signal can be degraded. You can check the space weather on the NOAA website. Photo European Space AgencyLightningGPS signals have to pass through the troposphere, which is where the weather does its thing. Moisture, dust and electromagnetic activity can bend and distort the signal. And when your signal fix is low on the horizon, it has to travel through the troposphere for a greater distance, and refraction has more effect.Dispersed SatellitesIf your fixes are clustered around one spot in the sky, it’s tougher to calculate an accurate trilateration. Ideally you have satellite fixes from all corners of your field of view. Photo Wikimedia CommonsMultipath Gps ErrorIf a GPS signal bounces off something like a canyon wall or building, the timing of the signal will be off. This is called “multi-path error.”Gps JammerAlthough not common, GPS jammers are a real thing. You might be picturing something like this Air Force GPS jammer, but today you can buy them online for a few hundred bucks and they are the size of a hardback book. The concept is pretty simple, just broadcast a powerful signal on the same frequency as the GPS signal. It’s not really an issue for most folks, but it is common in the Eastern Mediterranean (Syria, Isreal, Gaza, etc.). A GPS jammer can also broadcast an incorrect signal, fooling a GPS into thinking it is somewhere else. Can the government reduce the accuracy of a GNSS ? Yes. For the US GPS organization, there is a sport called Selective Availability that degrades the accuracy. The estimate is that the government degrades public GPS when it might benefit an foe, etc .. It was rarely used in the early days of GPS, and nowadays is “ permanently ” turned off by law. We all know that laws change, laws are broken, and who knows what the future holds. other GNSS systems can be degraded angstrom well .g Tower5g signals have been blamed for Coronavirus, mass bird deaths, and yes, GPS interference. I’m not sure if it’s valid, but the Pentagon and FCC are squabbling over it now. If you see a tower like this out on your hike and the GPS doesn’t seem quite right, 5g could be the culprit. Photo Ericcson last, you can have hardware or software problems at any point in the march. sometimes satellites malfunction, or orbits change slightly because of gravitational shifts. When this occurs the GNSS providers broadcast “ fixes ” for the issues ( more late ). Satellites can besides go down because of malfunctions and service ( and you can check their condition here ). You can flush have software errors on the GPS telephone receiver conclusion. In 2020 many GPS units were off because the Sony GPS chipset did n’t account for the fact that the year had 53 weeks. Problems like this are normally addressed through firmware updates, so make sure your unit is up to date.

New GPS Bands

Gps BandsGNSS systems broadcast their signals on different frequencies. Just think of it as different radio stations on broadcast radio. Newer bands use more efficient encoding to transmit data quicker and more reliably. Chart by Tallysman I mentioned that the foremost GPS constellation became operational in 1993. Well since then, technology has progressed and GPS has vitamin a well. Today the US is launching the third generation of GPS, competently named GPS 3. For the GPS end-user, this equates to newfangled GPS bands. here ‘s what the GPS bands are all about .

Band Year Started Description
L1 1993 This is the original GPS band. It’s the slowest and does the worst job at traveling through objects.
L2C 2005 It’s a newer signal that’s more efficiently encoded and penetrates objects better. It’s generally combined with an L1C signal which allows it to correct some ionospheric errors.
L5 2010 GPS 3 satellites support the L5 frequency which has a stronger signal and is encoded the most efficiently. It’s considered “the best” positioning frequency that you can receive outside of encrypted military options.
L1C 2018 Think of this new signal as a “connector” signal that allows GPS to slot in more efficiently with other GNSS systems.

New GPS satellites are backward compatible. therefore global positioning system 3 satellites not entirely broadcast L5 signals, but besides L1. And not all satellites ( as of 2021 ) support the newer bands .Gpsmap 65 Satellite Screen Multi BandsNewer GPS units, like this GPSMAP 65s, and some phones support the newer GNSS bands. Just look for a GPS sold as “multi-band” and you should be good. Also note that other GNSS systems have their own version of improved bands, like the E5a band for Galileo shown here. Overall the new bands let signals to travel more efficiently, eliminating a dear amount of intervention. It means that the GPS unit can get a more reliable sign, ensuring a coherent position with every fix. sol while it might besides offer a more accurate position, it ‘s very the consistency of a good signal through varying conditions that is the game changer .

GPS Helpers

In an ideal global, your GPS would be 100 % accurate, but as you ‘ve seen, it ‘s not the reality with the stream GNSS systems. so versatile entities have come up with ways to improve the GNSS put know. Brace yourself of an attack of acronym .

WAAS & Satellite-based Augmentation Systems

Knowing that there can be scope and time errors with GNSS satellites, their operators have set up systems to monitors these errors, calculate corrections, and then broadcast the correction to users using a different sic of satellites. These are called Satellite-based Augmentation Systems ( SBAS ), and unlike the ball-shaped footprint of some GNSS systems, broadly only offer coverage in the home area of the hustler .Sbas Gps SytemsHere are the coverage area of the various SBAS systems. We live in a world covered with acronyms. Image European Space Agency For you as an end user, if you have the choice to “ enable WAAS ” as found on some Garmin units, do it. It can improve the accuracy of your status. note that receiving this extra signal and applying the corrections will require a bite more baron consumption from your GPS chipset .

Assisted GPS (A-GPS or A-GNSS)

When you beginning power your GPS on, it needs to acquire signals, read the data, and then predict the orbits and positions based on those signals. But the scope data and corrections for all the satellites is available on-line as a datum feed, then why not grab it from the a lot faster cellular or WiFi connection beginning ? That ‘s what A-GPS performs. The consequence is a much faster initial satellite fix and a small sum of might savings. Most smartphone GPS systems will have this built in, and evening standalone GPS units like a Garmin Fenix or handheld will download data when you sync with your call. On a Garmin they are called EPO or CPE files .

Differential GPS Systems

Dgps StationsContinuously Operating Reference Stations (CORS) are a series of worldwide stations that measure the difference between their GPS position and their surveyed position. If you know the precise surveyed side of a point, and compare it to your GPS position understand, you would know the beginning or difference. Once you knew how far off your GPS was, you could apply the difference to your data to get a precise position. This is called differential GPS placement. There is a cosmopolitan network of ground stations that monitor GPS differentials and provide that data for free to users ( USA and worldly concern locations ). The problem is that this derived function correction is n’t presently something widely supported in real-time, but as communications get more twist, it ‘s not out of the question for a hand-held GPS to access this datum and apply it. rather, you can upload your GPS datum ( saved as a RINEX file, a feature available on newer models like the GPSMAP 66 and Montana 700 ) to the NOAA OPUS locate, and then get back a corrected file. There ‘s other ways to do it deoxyadenosine monophosphate well, but that ‘s the kernel of it. It ‘s a fairly technical process, but hopefully in the future, it could be seamless and integrate into systems like Garmin Explore and Garmin Connect. The US Coast Guard and Army Corps of Engineers used to broadcast differential information over a radio signal, the Nationwide Differential GPS System ( NDGPS ). With the advent of WAAS and the new bands, it was discontinued in 2020 .

Real-Time Kinematic (RTK)

Rtk ReceiverIf you want maximum precision, RTK is the way to go. But don’t expect it to fit nicely into your backpack pocket. The gear is designed for surveyors. Photo Trimble RTK is the modern translation of derived function GPS. It uses a sophisticate method acting to determine satellite error and beginning at a al-qaeda station, and then transmits the offset to roving GPS units. Often the infection occurs over data networks rather of radio receiver waves. RTK is normally used by surveying to get a 1cm floor of accuracy. It ‘s therefore precise that RTK basal stations are used to measure tectonic plate movement. RTK receivers can have a cellular joining to access data in the field from root stations. RTK base stations are broadly accessed by a pay subscription, but there are some publicly available RTK stations. You can even set up your own RTK base station .

GPS Positioning Today and Beyond

Modern GPS chipsets can receive multiple signals from multiple GNSS systems simultaneously. From there, they can evaluate factors such as the signal quality and force, pick the best options, and then calculate your status. They can besides use different combinations of satellites and signals to simultaneously calculate multiple military position fixes and perform statistical analysis to refine them promote. As GPS chips become more sophisticated and efficient, the more variables they can evaluate and the more calculations they can perform .Klm Ecommerce Airport Navigation 01GPS chipsets are evolving into “positioning” chipsets that not only use GNSS but also other location services. For example, if you are in the Amsterdam airport, Bluetooth beacons can guide you from gate to gate. Photo KLM Modern GNSS chipsets determine your situation based on

  • a combination of GNSS signals
  • new GNSS bands
  • accelerometer input (also known as pedestrian dead reckoning or user dead reckoning)
  • position based on nearby WiFi and Bluetooth signals (works similarly to GPS positioning)
  • position based on cellular signals
  • real-time atmospheric data and compensation
  • 3D mapping of the earth’s surface

New smartphones with knock-down processors have the computing horsepower to evaluate all of these inputs and offer a very precise stead, probably leaving many dedicated hand-held GPS units in the scatter. For exemplar, newer phones like the Google Pixel 5 can get a GPS accuracy of about 3 feet. If you ‘re hiking, running, or bicycle, you credibly do n’t need much more preciseness than the width of your torso. For purpose-built outdoor GPS units from companies like Garmin, it will be baffling to compete with smartphones, particularly as phones get more broken and effective. Moving advancing I ‘d expect standalone GPS to offer universal adoption of the newer GNSS bands, better battery liveliness, and hopefully better chip logic and control. Integrating an RTK part ( either in real-time or cached when synced ) would besides be a big direction to out-perform the smartphone. It will be concern to see how the smartphone GPS versus dedicated GPS battle evolves.

GPS Tips

Fenix 5x Gps SettingsWhich GNSS should you choose? There’s always a fierce debate about whether GPS, GLONASS, or Galileo, or a combination of them works better. If battery life isn’t a problem, choosing the most GNSS systems should give you the quickest and most reliable position. To conserve battery, do a test using all the different combinations and see what gives you the best positioning versus battery drain. For some folks using only GPS can be fine.

  • If you need to choose between multiple GNSS bands or multi-band signals within one GNSS (like L1 & L2C & L5 in GPS), I’ve found that the multi-band within one system outperforms multiple GNSS systems.
  • One of the main power draws on a GPS unit is the GPS chipset use. If you have the GPS chipset working at full bore, recording every second using multiple GNSS systems, it’s going to consume more power. Every GPS unit is different, but the more features that you can “turn off” the less power that your GPS unit will consume.
  • Turn on WAAS if you have it and are okay with the battery drain.
  • Turn off “smart recording” and enable every-second tracking if you have that option. “Smart recording” uses inputs such as the accelerometer and heart rate to determine what data points to save, but the logic has been known to make bad choices. Setting recording for every second ensures that your position is always saved.
  • Sync your GPS with your phone or WiFi before using it. That will download the latest A-GPS files, check for firmware updates, sync your clock, and should allow you to acquire a GPS fix quicker. If you’re using the GPS after a long time or after traveling far, this is even more important.
  • Turn on your GPS and let it sit with a clear view of the sky for about 2 minutes before starting your tracking. This is called GPS Soak and gives the unit time to get a stable position.
  • Carry your GPS unit on a shoulder strap or top pocket, giving it a clear line of sight to the sky.
  • If you are buying an InReach GPS device, you probably won’t see GLONASS support. The InReach (Iridium) and GLONASS frequencies are close to each other, and transmitting in InReach would interfere with the GLONASS reception (or maybe even fry the receiver). In fact, on InReach devices like the GPSMAP 66i, the unit supports GLONASS but the software has it disabled.
  • Calibrate your compass and barometer if your device has them. These can be inputs for your GPS chipset.
  • On Android devices, turn on “high accuracy” mode by going to settings > location > mode > high accuracy.
  • On Garmin devices, enable 3-D speed and distance, which factors in elevation changes when calculating distance and speed. It should give you more reliable tracking data.
  • Pause your GPS when you stop. Why? Because if you have say, 10ft of accuracy, and you’re recording every second, each fix can be 10 feet away, recording about 600 ft of travel over 1 minute when stopped. This is called GPS nesting or drift.

Basic GPS Concepts in Use

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This Guide Was Written by Cris Hazzard

Cris Hazzard 4 Mile Trail Yosemite
Hi, I ‘m Cris Hazzard, aka Hiking Guy, a professional outdoors guide, hiking expert, and generator based in Southern California. I created this web site to partake all the big hikes I do with everyone else out there. This locate is different because it gives detailed directions that flush the begin hiker can follow. I besides share what hiking gearing works and does n’t so you do n’t waste money. I do n’t do sponsored or promote content ; I share only the gear recommendations, hikes, and tips that I would with my family and friends. If you like the web site and YouTube transmit, please support these free guides ( I could n’t do it without folks like you ! ) .

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