11 Replies
      Latest reply on Oct 11, 2019 1:13 PM by KMT
      cfc Level 1 Level 1 (20 points)

        I have noticed over the few months that the accuracy of the GPS in the iPhone has got significantly worse, both in terms of the horizontal accuracy reported by Core Location and the trails that I plot on maps.


        My app is a workout and mapping app for Apple Watch and it used to be that the accuracy was better when using the iPhone GPS, but now the Watch GPS is better.  I am not sure if this is due to my iPhone X or to iOS 11, but I suspect the latter given the time period. 


        My companion iPhone app allows the trail to be plotted on a map and graphed according to several values, including GPS accuracy, so it is ideal for highlighting the GPS performance.  The results from the Watch GPS are similar to before, but those from the iPhone GPS are dramatically worse at times.  In ideal conditions it is fine, but in less than ideal conditions it now struggles much more than before.


        Is anyone else having the same issues, and if so do they know a workaround?  Apple know about the problems because there are mutiple threads about it on their user forums, such as this one:




        Also, is there any way to force the app to use the Watch GPS even if the iPhone is present and connected?  This was never necessary before, but now that the iPhone GPS is unreliable (and unusable at times) I am getting more and more requests from users to provide it.

        • Re: Poor GPS accuracy on iOS 11 / iPhone X
          KMT Level 9 Level 9 (15,425 points)

          Can you put numbers to the accuracy involved?

            • Re: Poor GPS accuracy on iOS 11 / iPhone X
              cfc Level 1 Level 1 (20 points)

              It is difficult to compare because it looks like Apple have changed the way they report the accuracy to be more granular.  It used to be that I would usually (but not always) see multiples of 5m from the iPhone and multiples of 4m from the watch.  Now I get much more variation, going down to the metre.  It does look like the numbers are worse but given the change in reporting granularity I wouldn't like to say that proves that the GPS is less accurate.


              However the trails are visibly less accurate, especially when the signal is poor.  I often test my app whilst walking the dog, which involves the same 1 mile drive to some woods, then a 1 mile walk around the woods, and then a drive back.  The app is a workout app so I tell it that I am cycling for each of the drives.  The GPS definitely struggles more on the drives, taking longer to acquire the signal and often losing it, which was rare before.  The same happens in the woods but to a lesser degree.


              This is exactly the same route I have been taking whilst testing the app for almost a year (both me and the dog are creatures of habit!), so I am quite sensitive to the GPS performance.  However several users have said the same thing, and it only takes a quick Google of "iOS11 GPS" to see that many other users are seeing issues with all sorts of apps that use GPS.


              Does anyone know if there is a way to request GPS from the watch only?  It would also get round the issue where users start a workout within range of their phone and then move away.  This means the Watch GPS has to fire up part of the way into the workout, even if the user waits for a good GPS signal before starting.

            • Re: Poor GPS accuracy on iOS 11 / iPhone X
              Max_B Level 1 Level 1 (5 points)

              I'm the main dev' of a mapping application, using location service since 2009.

              I did'nt notice that fact (poor GPS on iPhone X) until customers started to report it. I have an X but did not pay attention to GPS accuracy on it at first because I was so used to a good result.

              I can see for sure that tracks (walking or riding, bike or horse, all tests in open field) are much less precise with my X than with my 7+. Also the altitude is very unreliable despite the verticalAccuracy value pretending to be 3m ! So are customers reports.

              Speculation on users forum are on internal chip or sofware driver modified for Galileo and recessing in the process. Hardware issue is likely since not all devices seem affected. Not found any Apple statement on this beside report from customers "this is a known issue".


              Also, the "GPS Diagnostic: Satellite Test" application on AppStore, show worst reception on the X.

              BTW, I wonder how this application and some others can gather satellites information, without using some sort of private API and still being approved. I'd love to be able to collect more information on GPS reception into my own app…

              • Re: Poor GPS accuracy on iOS 11 / iPhone X
                Svantulden Level 1 Level 1 (0 points)

                We are seeing similar problems for our iOS 11 users of iPhone X and 8.


                We have a Waze-like app that heavily relies on CLLocationManager and we are seeing strange CLLocations getting returned. Some have a correct speed and accuracy (under 10m), but without a course (-1). Also some of the logs we see have heavily switching accuracy, from 5m to 300m and back in a couple of location updates every second.


                This seems to occur more frequently in users of iPhone X and iPhone 8, however, we are also seeing reports of users that don't have those devices and also get invalid course. We are going to make a workaround to this problem to calculate the course ourselves when course is invalid.


                I've also found this article that maybe shows this problem occurring for users of iPhone X and 8: http://appleinsider.com/articles/17/11/09/some-iphone-8-iphone-x-users-suffering-from-gps-issues-software-fix-appears-to-be-coming-in-ios-112


                Though that should mean Apple fixed it in an iOS update, which doesn't seem to be the case for our users.

                • Re: Poor GPS accuracy on iOS 11 / iPhone X
                  4004 Level 1 Level 1 (0 points)

                  Not sure if this ever got fixed in any subsequent iOS update, but apparently a reboot with the sim ejected helps.

                  Had a 6s with very poor positioning and long waits for GPS lock, which was jumpy even then, with the above method fixing the issue (for now).

                  Could potentially suggest this as a workaround for those of your users experiencing issues

                    • Re: Poor GPS accuracy on iOS 11 / iPhone X
                      BrutalBob Level 1 Level 1 (0 points)

                      Before I did the trick ”rebooting with sim ejected” I would get between 30 - 200m accuracy.

                      After reboot with sim still ejected the gps immediately jumped to 5m accuracy. :-)

                      inserting back the sim, and accuracy still at 5m.


                      smells like the assisted gps using cell location information has a negative impact on the gps accuracy.

                      I read one story on internet of people complaning that there mobile provider needed to do an update of the phone sim settInga to get a-gps working, Mayby the a-gps data is corrupted and conflicting with satelite data, resulting in jumping accuracy?


                      Iphone 6s, iOS 11.4

                        • Re: Poor GPS accuracy on iOS 11 / iPhone X
                          alan.raceQs Level 1 Level 1 (0 points)

                          My understanding is that A-GPS only  improves the startup performance of a GPS receiver: it doesn't improved the subsequient accuracy of the position reports.

                          There is often a confusion between A-GPS, which improves startup performance,  and D-GPS, a much more sophistaced system, which improves the location accuracy of the GPS from metres to centimetres.

                        • Re: Poor GPS accuracy on iOS 11 / iPhone X
                          DrDirkP Level 1 Level 1 (0 points)

                          Unfortunately it did not work in my case. I have tried any fix options I found in the internet. Amazing how many people have been frustrated by GPS accuracy issues since iOS11. Unbelievable that Apple was not able to fix it. Users of my app are reporting similar issues with iPhoneX and iOS12.2 now. I was able to reconstruct it on my development iPhones. Until now I have not found a way to resolve it for my customers. The only option I have for the moment is to take the app out of sales... So, would be grateful if someone could help with an advice.

                        • Re: Poor GPS accuracy on iOS 11 / iPhone X
                          zuluzibar Level 1 Level 1 (0 points)

                          I just upgraded from iPhone 8 to iPhone 11 Pro - and the GPS accuracy has decreased so much.  I brought my phone in for repair because of how bad the GPS was and they gave me a new one, but the new one is pretty bad as well.  When I'm outside, my position on the map is constantly bouncing around a circle of about 250ft diameter.