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I have done some extensive testing of my iPhone 4S compared to my iPhone 4 and found GPS accuracy has suffered substantially.

I've been using the 4 for about a year, riding a bicycle on a 3 mile loop park road several times a week. Typically, I'll do about 6 laps or 18 miles. Using a great app called Cyclemeter, I save the track so I have a record of how fast and how far I rode. After I upgraded to the 4S I found the measured length of each lap varied widely and that ridiculously high speeds were being recorded.

Upon examination of the recorded track I find loops drawn out to points up to 100 feet from the actual course and back tracks heading the wrong direction. The net result is the iPhone 4S is off by around 20% on the measured distance from what I know it should be. Has anyone else looked carefully at their tracks and found similar results?

What is more likely: That I have a defective unit OR that Apple's elimination of a dedicated GPS chip means less accurate information?

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  • Shoot a mail to the developer. They can help you get to the bottom of the GPS and also understand / tweak how their app is filtering and processing the raw location data from your devices.
    – bmike ♦
    Commented Nov 28, 2011 at 6:40
  • I'm with @bmike. It sounds like an issue with the app, not the hardware (read: iPhone 4S). The 4S has different hardware from the it's predecessor so it's quite likely a matter of supporting it. If anything, it should be more accurate.
    – user10355
    Commented Nov 28, 2011 at 13:37
  • I have the same problem. I usually run the same pattern every day (10 laps). My iPhone 4 had it's ups and downs concerning the accuracy but it never was as bad as the 4 s. 4 was most of the time perfect while the 4 s depicts me in the stadium but on different lanes. I tried turning off wifi and cell data but I think it did not affect it much. I have to say that when I used the ip4 I had always 3G off which Is imPossible with the 4s. I think that has something to do this problem.
    – user17368
    Commented Jan 18, 2012 at 1:20
  • As a developer, I'm going to blame the hardware, unless the developer updated the app and changed the API call used, to preserve your battery life. Apple changed the hardware, but the APIs remained unchanged.
    – Moshe
    Commented Feb 16, 2012 at 21:17
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    I would argue that Apple has tried to improve, not degrade the location capabilities and accuracy with the iPhone 4S. One of the major new features of iOS 5 (which came out the same time as the iPhone 4S) is the Reminders app, and one of its capabilities is producing a reminder alert when arriving at or leaving a location (using so-called geofences). Apple's style is to evolve the hardware and the software together, so launching this geofencing feature was likely done with the expectation that the 4S would excel at determining device location.
    – bneely
    Commented Feb 16, 2012 at 21:49

3 Answers 3

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My experience helping others with this problem seems to suggest a few things:

  • Apple's been monkeying around with power conservation by trying to give "good enough" positioning results while idling the GPS for longer periods and relying on cell tower and wifi positioning more. Try turning off wifi for your next run to see if the GPS does better (and if your battery is drained more).
  • Application developers are decreasing the GPS resolution of their apps in order to have less impact on the battery due to user complaints. Check to see if the app you use can be configured for GPS update frequency and ask the app developer what they suggest regarding your problem.
  • Both the iPhone 4 and 4S seem to suffer from GPS degradation after awhile that can be fixed by doing a refresh of the device - in other words sometimes it's a software issue that seems to fix itself after a hard reboot and system refresh. For some people a hard reboot is sufficient, but others have indicated that only a refresh will work for them. I think this started affecting some of my friend's phones around the beginning of last summer. I've seen several of my friends have this issue, visit the store, have it refreshed and reset, and the problem disappear. Now they do the refresh themselves with iTunes when it gets annoying. I don't have information on whether this is tied to a particular version of iOS or not, but I have seen it on both the 4 and 4S.

Of course you could also be experiencing a hardware problem, but you might consider some of the above actions before completely blaming the hardware.

Also be aware that GPS requires good line of sight to the sky. If you've changed your iOS device position recently, consider changing it back. If you're wearing it, make sure your body isn't between the device and the sky, and that your perspiration isn't reaching the device.

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I believe this is a hardware problem. I had an iPhone 4 using the RunKeeper app similar to Cyclemeter. It worked perfect for six months, then GPS accuracy degraded (says I ran a little over double my actual distance and the map shows data jumping all over about 250 yards off track). Behaves like signal blockage. Not caused by dropping, heat, power, etc. Per Genius suggestion, I tried disabling all other Locator apps as well as tricks you reported. Eventually, Apple replaced the iPhone under warranty with a new one which worked perfect for three months, and this week it began degrading as well (useless for running!). Since the original 1 year warranty is up, I'm stuck! Apple Genius Knowledge Base does not address this issue. They say the GPS either works or it doesn't, and it doesn't degrade accuracy or get intermittent data points. They have no fix.

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    If it doesn't work as it should, take it to Apple anyway and they will likely fix it (though try to aim for a time where they won't be busy), even out of warranty, given that you've had the problem before they should be more liekly to help. they care about what people think of them, so if you come back here and say the replaced it for you, it's good for them.
    – Jonathan.
    Commented Mar 19, 2012 at 23:27
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The iPhone 4s contains a GLONASS chip, in addition to the GPS chip (at least for units sold in North America and Russia). GLONASS is the Russian competitor to the GPS. Theoretically, it should improve accuracy, since iPhone samples both chips, but I don't think that happened. In my case, the GPS seems 3-4 seconds behind what I am doing.

I am guessing this is new to Apple and all the problems get fixed in the next update.

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    GLOSNASS CDMA is not yet in operation. The added functionality is just a trick to avoid customs when importing into Russia.
    – bot47
    Commented Nov 28, 2011 at 21:14
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    @bot47 GLONASS has nothing to do with CDMA. The business with customs maybe correct, I don't know.
    – AngryHacker
    Commented Nov 29, 2011 at 19:42
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    Yes it does. I'm not talking about CDMA as the unfortunately named US mobile phone network standard, but about CDMA as the multiplexing algorithm "Code Division Multiple Access". AFAIK today GLONASS uses Frequency Division Multiple Access (FDMA).
    – bot47
    Commented Nov 30, 2011 at 7:58

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