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What is GPS? The Beginner's Guide
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What is GPS? The Beginner's Guide

What Is GPS? The Beginner’s Guide

GPS stands for Global Positioning System. It’s one of several advanced navigation systems known as global navigation satellite systems (GNSS). Using a network of more than 30 satellites, GPS can calculate an object or person’s position and speed anywhere in the world in any weather conditions.

The US Airforce first began developing GPS for military operations in the 1960s, but they made the system public in the 80s. It’s completely free, and anyone can use it—as long as they have a device that connects to it. 

GPS has a wide variety of personal, commercial, and military applications, all of which relate to positioning, navigation, and timing (PNT). In this guide, we’re going to explore some of the main ways consumers and businesses use GPS, but we’ll also look at how GPS works and how reliable it is.

By the time we’re finished, you’ll have a solid grasp of what this technology is capable of and why it’s trusted all around the world.

Let’s get started.

How does GPS work?

GPS works when your device collaborates with a network of satellites in orbit to solve some advanced geometry puzzles.

When you use a GPS-enabled device—whether it’s on your phone, a smart watch, or a GPS in your car—it picks up a signal from the network of GPS satellites orbiting the Earth. Those satellites follow a precise, predictable path and transmit a unique signal with their exact location and the time. As long as your device is within range of four or more of those satellites (which is almost all the time), the GPS uses “trilateration” to calculate your position.

Basically, GPS knows the location of the satellites in orbit, and it uses those four (or more) known locations to identify the “unknown” location of your GPS device, judging by the amount of time it takes your receiver to pick up the signals from the satellites.

The GPS knows the speed each signal travels and where it started from, so when your device picks one up, the GPS multiplies the signal speed by the time it took to reach you, telling it how far the signal travelled to get to you. In other words, the system can say “this device is [distance] from this satellite.” 

Add positioning data from the other satellites, and it can give you a pretty accurate reading of where in the world you are, and how far you moved since it last identified your location. (Although if you’ve ever driven around a complicated freeway overpass, you know they can get a little confused sometimes!).

How accurate is GPS?

The latest performance data the US government has released claims GPS can determine your location within 4 meters, and that it’s 95 percent accurate within 7.8 meters. So does it know exactly where you are? No. But it’s pretty darn close.

Part of what makes GPS work is that each satellite has an atomic clock, and they’re all synchronized with each other and with clocks on ground stations located around the world. If these clocks get out of sync, GPS won’t work—so the satellites’ clocks constantly correct themselves to align with the ground clocks. (Being in space messes with them.)

There are a few things that can make your GPS more or less accurate than average.

In general, GPS is most accurate when you’re in range of more satellites (because there’s more data available to determine your location). So while it works anywhere in the world, your location can still throw off GPS signals if something gets between you and the satellites

Think about it: GPS calculates your location based on the time it takes your device to receive the satellite signal. If something slows down, blocks, or reflects the path of the signal, then the data that satellite adds to the equation is going to be wrong. 

So if you’re indoors or below ground, it may not work at all. Mountains, buildings, and even trees can decrease the accuracy of your coordinates. GPS is always going to work best in wide open areas where there’s a clear line of sight between you and the satellites. 

The GPS receiver you use can also affect how accurate the readings are. Low quality GPS receivers can produce low quality readings. Poorly designed GPS devices may not meet GPS interface specifications, or they may have inaccurate (or outdated) mapping software.

The most accurate GPS receivers are dual-frequency receivers, meaning they use two GPS frequencies, which helps them correct any distortions caused by the atmosphere. This is what the military uses, and they’re available for civilian use as well—but they’re pretty bulky and expensive, so they’re mostly used in professional settings.

You can also use augmentation systems to further increase the accuracy of your GPS with additional navigational, timing, or positional data. Additionally, you may be able to connect to other global navigation satellite systems—like Russia’s aptly named Global Navigation Satellite System (GLONASS)—to access additional satellite positioning information.

Fun fact: In the 1990s, the US government was afraid of the potential ways people could abuse GPS, so they released a “Selective Availability” feature to intentionally degrade the quality of civilian GPS readings. In 2000, this feature was discontinued to ensure GPS could provide the maximum benefit to civilians and businesses.

What can you use GPS for?

GPS has numerous applications related to position, navigation, and timing (PNT). A lot of them are pretty similar or only apply to specific niche situations, so we’re just going to focus on the most common use cases.

Choosing the best route

Whether you’re driving, walking, or taking another form of transportation, GPS has become an essential tool for determining how to get where you want to go. While a map can show you a route, GPS shows you that route in relation to your location. It removes the guesswork and tells you where to turn next, how long it will take to get where you’re going (based on speed limits, distance, etc.), and even alternative routes to your destination.

Interestingly, one of the main values GPS provides today actually comes from the proliferation of GPS devices: GPS can use data from other GPS users to recognize when there’s a traffic slowdown—which helps it determine if there’s a faster way to get where you want to go.

It can’t tell you if the slowdown is due to construction or a car accident. But when there are people stopped or slowing down on your route, and they have GPS-connected devices, your GPS receiver may be able to use that data to predict a better route.

Determining the best route for vehicles is part of the field of vehicle telematics, and it’s an essential function of fleet management.

Tracking your runs

Another common way people use GPS is to record how far they run or walk. Mobile apps and smart watches use GPS to record your position and track your movement during your workout, and you can tell them when to start and stop to get a reading of how far you’ve gone. These apps don’t just tell you how far you traveled—they also use GPS data to map your pace throughout your route and even tell you how much elevation you climbed.

Checking the weather

You can always Google “weather in [city]” to pull up data from the most prominent weather stations. But if you turn on location data, your mobile device will use GPS to identify the nearest weather station and pull its most recent information, giving you the most relevant data about the temperature, humidity, chance of precipitation, and wind speed.

Most of us today are so accustomed to seeing the local weather on our phone that we may not even realize this is being enhanced by GPS.

Local search results

Anytime you use Google to search for “Thai food” or “mechanic near me”, Google uses GPS data to create a list of local businesses that fit, along with how far away they are. If your device has location data turned off, Google’s “local” search results become less helpful.


Geofencing uses GPS to create a virtual “fence” around a geographic area. It’s a core GPS concept that enables some of today’s most valuable and innovative GPS functionality. Depending on the geofence’s purpose and how it’s configured, when a GPS-enabled device leaves or enters the specified area, the fence triggers a notification either to that device or a separate device. 

Geofencing is often a component of mobile apps. An app can use geofences to send notifications to people who leave or enter particular locations to notify them about deals, desired actions, events, or location-related information. Someone might also use an app with geofencing capabilities to monitor their valuable assets—if something leaves the premises that isn’t supposed to, they’ll be notified. 

This all relies on GPS to determine where a device is, so the app knows whether or not that device should receive or trigger a notification. It’s how people use GPS to find lost items or pets, and it can be extremely helpful for caretakers of those who have dementia, Alzheimers, and other conditions that may cause them to get lost. 

Fun fact: Digital advertisers also sometimes use geofencing to ensure their ads only display for people in specific locations.

Finding lost items

Today, when you have something you can’t afford to lose, you can put a small GPS receiver on it to ensure that you always know its (almost) exact location. Same goes for if your property is stolen. Or if you just misplaced your keys again. Depending on the app and device you use, this may also use geofencing to notify you when the device leaves a specified area. A lot of people also use GPS devices to track their cars or recover missing bikes.

Spytec’s STI GL300MA GPS tracker is perfect for helping you recover lost or stolen property. It’s highly portable and the battery lasts 2.5 weeks. Plus you can track in real-time and get email or text alerts.

Staying safe on adventures

Whenever you travel, it’s always important to make sure someone else knows where you are. Whether you’re alone or not, you want to trust that if something doesn’t go according to plan, someone will be able to get help—and that help will know where to find you.

Out in the wilderness, you may not have cell phone reception, but as long as you’re in a clear area, your GPS signal should come through. Some mobile devices today allow you to share your location with other devices in your account settings, but there are also apps and other GPS devices you can use while hiking, backpacking, or traveling abroad to ensure someone knows where you are in cae of an emergency. (It will also help to give them your itinerary, so they know where you should be, too.)

Receiving emergency alerts

Every time you receive an Amber Alert or an emergency notification about weather and other safety-related events, this uses GPS data (and geofencing) to determine if you should receive the notification. This is an incredibly valuable public safety innovation, as it allows the government to immediately alert anyone who may be impacted by a disaster or who could help law enforcement by taking a quick look around them.

On a related note, social media platforms may also prompt people near a disaster to indicate if they’re safe to help prevent others from worrying about them. One of the first things people do when they hear about a major disaster is think about anyone they know who may have been nearby. So this helps dissipate panic by encouraging people to publicly put their friends and family at ease.

Fleet management

Companies that rely on transportation or have a lot of machinery spread across a range of sites use GPS to manage and track their vehicle fleets. Fleet management is intended to help companies improve efficiency, reduce costs, and comply with regulations. And an essential component of fleet management is vehicle tracking, which is key to monitoring and optimizing things like:

  • Fuel efficiency
  • Speed
  • Safety
  • Route optimization
  • Vehicle usage

This is especially important for companies that work in industries like transportation, shipping, and construction. And it’s just as important for boats and aircraft as it is land-based vehicles. Some fleet management systems may also use geofencing to ensure drivers and/or vehicles stay within designated areas.

Our customers use GPS trackers for things like:

  • Construction
  • Maid/Cleaning services
  • Moving companies
  • Lawn services
  • A/C repair

Any organization that has company-owned vehicles they want to protect or optimize should be using GPS trackers.

Want to see some GPS devices?

At Spytec, we specialize in GPS equipment for personal and commercial use. Whether you just want to protect your property against theft or manage a fleet of vehicles, we’ve got solutions for you.

Take a look at our GPS devices.


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