How GPS Works on the iPhone

Location, orientation, and motion technology used by the iPhone

Your iPhone includes a GPS chip like the one found in stand-alone GPS devices. The iPhone uses the GPS chip in conjunction with cellphone towers and Wi-Fi networks in a process called assisted GPS to calculate the phone's position quickly. You don't need to set up the GPS chip, but you can turn it off or enable its functions selectively on the iPhone.

Information in this article applies to iPhone 7 and later.

GPS Systems

GPS is short for the Global Positioning System, which is a system of satellites put into orbit and maintained by the U.S. Department of Defense. GPS finds a position through trilateration that uses at least three of a possible 31 satellite signals.

Other countries are developing systems, but GPS is the only one in wide use around the world. The only other system that is close in capability is Russia's GLONASS satellite system. The iPhone is capable of accessing both the GPS and GLONASS systems.

One weakness of GPS is that its signal has trouble penetrating buildings, deep woods, and canyons, including urban skyscraper canyons. In these instances, cell towers and Wi-Fi signals give the iPhone an advantage over stand-alone GPS units.

Controlling GPS on the iPhone

Although an active GPS connection is essential for apps that offer navigation and mapping features, there are privacy concerns related to its use. For this reason, the iPhone contains several areas where you can control how and whether the GPS capability is used on the smartphone.

How to Turn Off All Location Technology

You can turn off all location technology, including GPS, on the iPhone, although Apple does not recommend it. Here's how:

  1. Open Settings on the iPhone.

  2. In the Settings menu, select Privacy.

  3. Tap Location Services at the top of the Privacy screen.

  4. Tap the Location Services toggle to change it to the Off/white position.

  5. Select Turn Off in the confirmation screen that appears.

    iPhone settings with Privacy, Location Services, and the Turn Off command highlighted

Limit GPS to Only Some Apps

You can take a more specific approach by limiting or granting access to GPS information for specific apps. You can set when an app is allowed to access GPS information and other location technology to Never, While Using, or Always.

  1. Tap Settings > Privacy > Location Services to return to the Location Services settings screen.

  2. Move the Location Services toggle to the On/green position if it is turned off.

  3. Scroll down to the list of apps on the iPhone and tap one.

  4. Select Never, While Using the App, or Always to regulate GPS and other location technology usage for that app.

    The iPhone Location Services settings
  5. Repeat the process with each app on the list.

Limit GPS for System Services

Apps aren't the only things on an iPhone that use GPS technology. Apple System Services also use location technology. You might want to turn off location-based Apple ads, for example, but turn on your location for emergency calls and SOS services.

To locate this setting:

  1. Tap Settings > Privacy > Location Services to return to the Location Services settings screen.

  2. Scroll to the bottom of the screen and tap System Services.

  3. Tap the toggle next to each service to activate or turn off location services, including GPS, for that service.

    iPhone System Services and an off switch

You may see an arrow next to one or more of the System Services.

  • A gray arrow indicates that the service used your location in the previous 24 hours.
  • A solid purple arrow means that a service used your location recently.
  • An empty arrow indicates that the item it is next to may receive your location in some instances.

GPS Complementary Technologies

The iPhone includes several complementary technologies that work in conjunction with the GPS chip to master the phone's location.

  • Accelerometer and gyroscope: The iPhone has a small six-axis gyroscope and accelerometer combination chip. The gyroscope tracks the orientation of the phone, such as whether it is held upright or on its side. The accelerometer detects and records motions the phone experiences, big and small, as data the phone and apps can use.
  • Wi-Fi tracking: When GPS doesn't work well, such as inside buildings or among tall buildings, Wi-Fi tracking replaces or supplements it. Wi-Fi tracking uses a database of Wi-Fi networks around the world to triangulate the phone's position based on multiple Wi-Fi signals.
  • Compass: The iPhone has a digital compass as part of its motion-tracking chip. The compass supplements other motion technologies and orients maps on the phone.
  • Barometer: You might think a barometer, which measures air pressure, is primarily a weather-prediction device, but it's not used for that purpose on an iPhone. The barometer supplements the GPS chip and measures elevation changes to create accurate elevation and elevation-change readings.
  • M-series Motion Coprocessor: The iPhone uses Apple's motion coprocessor chip to continuously measure data from the accelerometer, compass, gyroscope, and barometer. ​The coprocessor offloads work from the main processing chip for improved power efficiency.