GPS is a system to estimate location on Earth by using signals from a set of orbiting satellites. The GPS system includes the chip in your iPhone device as well as the satellites above the Earth.
- Examples of GPS issues
- Achieving an initial GPS lock
- Troubleshooting steps
- Variable performance
Examples of GPS Issues
If you experience any of the below, your activity may report a different distance than you actually traveled and, unfortunately, it will not be possible for us to "fill in" the missing data or modify the existing data. Thankfully, there is more that can be done to prevent bad GPS data from being recorded than there is to repair it. Please refer to the troubleshooting steps listed in this article to prevent similar issues in the future.
- GPS drift: The GPS track deviates from the road. You may see that the route generally follows the shape of the road but with much less precision.
- Lost GPS signal: If the GPS signal is lost and sometime later re-acquired the pre- and post-signal-loss points will be treated just like any other two points (although more time has elapsed between them) and connect them with a straight line.
- GPS bounce: A 'jumpy' GPS track can cause your activity to report more distance than you actually traveled since each 'zig' and 'zag' of your GPS track has to be accounted for with a straight line connecting them.
Achieving good initial GPS lock
To achieve fast startup and high-accuracy position estimates, you should provide:
- A clear view of a large portion of the sky. Any obstructions between the phone and the sky can adversely affect signal strength. A big tree is an obvious obstacle, but even a pocket or a backpack can cause problems for the very low-strength signals.
- Time to tune in to the signals from the satellites. To improve signal acquisition time, keep the device in one place and make sure the device's data communications are enabled. This allows the phone's GPS to get hints about its approximate location. Even with a perfectly clear sky, it can take a few minutes before a lock can be established in some situations.
Steps to take when investigating GPS Issues on iOS devices
- Turn your phone off/on.
- Turn location services off/on.
- Close all other open applications before recording and if you open another app during your activity, navigate back to Strava afterward.
- Ensure that your phone isn't connected to a WiFi network when you start your activity.
- Open Strava when you have a clear and unobstructed view of the sky and wait a few more minutes than normal before starting your activity even if you see a message that says 'GPS Signal Acquired.'
- Perform a GPS reset:
- Double-tap the home button. This will bring up tile sized images of all currently running apps. Swipe the screens of all apps upwards to close them.
- Then go into settings and turn on airplane mode.
- When you've done that go to settings, general, reset and choose reset network settings (you will need to re-enter your wifi passwords!)
- Once your phone has reset go to settings, location services, turn it off then on again.
- Then go settings > privacy > location services > system services, setting time zone OFF.
- Some devices may have apps installed that disable GPS services or terminate backgrounded apps in an attempt to reduce battery usage and improve system performance. Examples of apps in this category include "Advanced Task Killer" and "Juice Defender." Please disable or adjust the settings of these apps to allow Strava to receive GPS information during long periods of background operation.
- Final Steps
- Try using the Strava app to record for 10 minutes, letting it search for signals with a wide-open view of the sky, and keeping it completely immobile.
- If this does not produce useful location estimates, determine if GPS works in other apps. It's best to use another fitness tracker app and not a navigation app like Google Maps, Waze or Apple Maps. Navigation apps use cell towers to snap your position to known roads and trails which can give the illusion that your GPS is working perfectly. Strava and many other fitness apps do not do this and just use GPS to position you. Because of this, you may notice Strava is having a hard time locating you but other navigation apps aren't.
The GPS system includes the chip in your device as well as the satellites above the Earth. So even if your device is in the same place and the same setting as before, it may behave differently from one day to the next. Typically, the device needs to receive signals from about 5 satellites to get an accurate estimate of its position. With the changing position of the satellites, changing weather patterns, and the changing nature of the Earth's outer atmosphere, there are enough parts of the GPS system outside of your direct control and observation that it is difficult to make conclusions about what specifically is causing inconsistent performance. We recommend you try all the suggestions listed above thoroughly before making a judgment about the best ways to work with your device's GPS.