GPS works by receiving signals from satellites orbiting Earth and using those signals to pinpoint your location. You don’t need to pay for a subscription, install special equipment, or even have an internet connection to use it. Every modern smartphone has a GPS receiver built in, and getting started is as simple as opening a maps app and letting it find your position.
How GPS Determines Your Location
A network of satellites constantly broadcasts radio signals as they orbit the planet. Your phone or GPS device picks up these signals and measures how long each one took to arrive. Since the signals travel at the speed of light (roughly 300 million meters per second), the receiver can calculate exactly how far away each satellite is using a straightforward formula: distance equals speed multiplied by travel time.
Once your device knows its distance from at least three satellites, it uses a process called trilateration to narrow down your position. Think of each satellite’s signal as defining a sphere around that satellite. Where three or more of those spheres overlap is where you are. In practice, your device connects to four or more satellites to get a reliable three-dimensional fix that includes altitude.
Using GPS on a Smartphone
To use GPS on your phone, make sure location services are turned on. On most devices, you’ll find this in Settings under “Location” or “Privacy.” Once enabled, any app with location permission (Google Maps, Apple Maps, or a hiking app) can access your GPS coordinates.
Open your preferred maps app, and a blue dot or arrow will appear showing your current position. From there you can search for a destination, get turn-by-turn directions, and follow the route in real time. The app combines your GPS position with map data to guide you. While the maps themselves require an internet connection to load initially, the GPS chip in your phone receives satellite signals directly and works independently of cell service or Wi-Fi.
One common misconception is that GPS uses your mobile data. The GPS receiver itself doesn’t consume data at all. What does use data is downloading the map tiles and traffic information that make navigation apps useful. This distinction matters when you’re in areas without cell coverage, which brings us to offline maps.
Navigating Without Internet
You can use GPS even when you have no cell signal or Wi-Fi, as long as you prepare in advance. In Google Maps, search for the area you need, swipe right on the location card, then tap “More” followed by “Download offline map.” This saves the road network and points of interest to your phone’s internal storage or SD card. Apple Maps and other apps like OsmAnd offer similar offline download features.
Once downloaded, your offline maps work with your GPS receiver to provide driving directions just like they normally would. The main limitations: you won’t get real-time traffic updates, alternate route suggestions, or public transit and walking directions while offline. You also need to make sure your downloaded area covers your entire route, not just the destination. For road trips through remote areas, download generously sized regions before you leave.
What Affects GPS Accuracy
Under open sky, a typical smartphone GPS is accurate to within about 5 meters (16 feet). That’s precise enough for driving directions, finding a trailhead, or locating a business. Several factors can degrade that accuracy significantly, though.
Tall buildings are the biggest everyday problem. In dense urban areas, GPS signals bounce off glass and concrete before reaching your phone, a phenomenon called multipath interference. Your receiver picks up both the direct signal and these reflected copies, which confuse the distance calculations. In narrow streets surrounded by skyscrapers, your phone may struggle to track enough satellites at all, or it may place you on the wrong block. Dense tree canopy, deep valleys, and even heavy cloud cover can weaken signals for similar reasons: longer or obstructed paths between satellite and receiver reduce signal strength.
If you notice your position jumping around on the map, try moving to a more open area. Standing near the center of a street rather than under an awning, or stepping out from under heavy forest cover, often helps your device lock onto more satellites and settle on an accurate position.
GPS vs. Other Satellite Systems
GPS is the U.S.-operated satellite constellation, but it’s not the only one. Russia operates GLONASS, the European Union runs Galileo, and China maintains BeiDou. All four systems do the same thing: broadcast positioning signals from orbit. The umbrella term for all of them is GNSS (Global Navigation Satellite System). GPS has become the generic word for satellite navigation the way “Kleenex” stands in for tissues, but most modern smartphones actually connect to multiple constellations simultaneously.
This matters for you because more satellites means better accuracy, especially in challenging environments like cities or mountain valleys. A phone that can see GPS, GLONASS, and Galileo satellites at the same time has far more data points to work with than one relying on GPS alone. You don’t need to configure anything for this. If your phone supports multiple constellations (most made after 2018 do), it uses them automatically.
Augmentation Systems for Better Precision
In North America, a system called WAAS (Wide Area Augmentation System) corrects GPS errors caused by atmospheric interference. Ground stations across the continent measure the actual errors in GPS signals and broadcast corrections through geostationary satellites. Devices that support WAAS, including many handheld GPS units and newer smartphones, can achieve accuracy better than 3 meters about 95% of the time. In testing, position error dropped from around 1.7% to 0.45% when WAAS corrections were applied alongside standard GPS.
You don’t need to do anything special to benefit from WAAS if your device supports it. The corrections are applied automatically when your receiver can see the WAAS satellites, which cover most of North America.
Saving Battery While Using GPS
GPS hardware draws meaningful power when it’s actively tracking your position. On a long drive or hike, that drain adds up. A few practical steps help. Close other apps you’re not using while navigating, dim your screen brightness, and plug into a car charger or carry a portable battery pack for longer trips. Most phones also offer a “battery saver” location mode that uses Wi-Fi and cell towers for approximate positioning instead of the GPS chip. This saves power but sacrifices accuracy, so switch back to full GPS when you need precise navigation.
If you’re using a dedicated GPS device like a Garmin handheld, battery life is typically much longer than a smartphone because the device isn’t also running a browser, email, and background apps. For backcountry trips lasting multiple days, a dedicated unit is often the better choice.
GPS for Outdoor Safety
A standard GPS device or phone app tells you where you are, but it can’t call for help. If you’re heading into areas without cell service, it’s worth understanding the difference between GPS navigation and satellite emergency devices.
A Personal Locator Beacon (PLB) sends a one-way SOS signal to search and rescue through a dedicated satellite network. It has a powerful 5-watt transmitter that can push through dense tree cover, requires no subscription fee, and does one thing reliably: alert authorities to your location in an emergency. The trade-off is that communication is one-directional. You can’t exchange messages with rescuers.
Satellite messengers (like those from Garmin or SPOT) offer two-way text messaging, SOS capability, and often include basic navigation features. They use a weaker 1.6-watt transmitter and require a monthly subscription starting around $15, but the ability to communicate back and forth with rescue teams and send non-emergency messages to family makes them more versatile. For serious backcountry use, carrying one of these alongside your GPS navigation setup adds a critical safety layer that GPS alone doesn’t provide.
GPS Spoofing and Signal Reliability
GPS signals are relatively weak by the time they reach Earth’s surface, which makes them vulnerable to interference. Spoofing, where someone broadcasts fake GPS signals to trick a receiver into reporting the wrong location, is a real and growing concern. Inexpensive radio equipment can jam or manipulate GPS data, and researchers have demonstrated the ability to offset a vehicle’s perceived location by up to 10 meters in any direction.
For everyday navigation, spoofing is unlikely to affect you personally. It’s primarily a concern for autonomous vehicles, shipping, and aviation. But it’s worth knowing that if your GPS suddenly places you in a wildly wrong location and your surroundings haven’t changed, the issue may not be your device. Restarting the app or moving to a different area usually resolves ordinary glitches. Persistent, dramatic location errors in areas where GPS normally works fine could indicate local signal interference.