How to Reset the GPS on an iPhone

If your iPhone is experiencing difficulties detecting your geographical location using its built-in global positioning system, you can turn the GPS reception off to reset it. The iPhone makes use of a digital compass and gyroscopic sensor to determine your physical location, and it may not be immediately obvious which of these sensors is causing the location detection problem. Recalibrating all the sensors during a GPS troubleshooting procedure ensures the appropriate hardware has been properly reset.

...
The iPhone doesn't have a setting for switching GPS on and off.

Step

Launch the Settings application on the iPhone by tapping its icon on the home screen.

Step

Slide the "Airplane Mode" switch to "On." This disables all the iPhone's radio reception hardware, including GPS. Wait for approximately one minute and then slide the "Airplane Mode" switch to "Off." The iPhone reconnects to all its radio services.

Step

Launch an application that makes use of the iPhone's gyroscope and digital compass hardware, such as the native Maps or Compass apps.

Step

Physically move the handset in a large figure eight pattern several times to recalibrate the gyroscope and digital compass. The application should be running during this procedure to ensure the iPhone has activated the sensors you are recalibrating.

Step

Hold the iPhone's Power button for two seconds and slide the red "Slide to power off" button on the screen to the right if the device is still exhibiting GPS problems. This shuts the iPhone down.

Step

Wait for approximately one minute and press the Power button again for two seconds to start the iPhone up again.

Step

Contact Apple's customer support or take the device to an Apple Store if it is still exhibiting GPS problems and explain the troubleshooting procedures you have attempted.