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Verizon iPhone 4S: Problem with inaccurate GPS tracking

I've tried using the iMapMyRun+ app to track my runs on the Verizon iPhone 4S twice now and each time I've noticed afterward on the map of my run that the phone shows me zig zagging across the street, running through people's yards, and sometimes breaking into people's houses just so I can run through them... and all at an amazing speed.


These deviations from my actual course add considerable distance to my run and results in wildly inaccurate pace readings, making it almost impossible to use the phone to practice my pace. The only reason I'm test driving an iPhone is because it's supposed to be a better phone for runners since there are some really useful accessories available for the iPhone (and none for Android). So this GPS problem is a deal breaker for me. I uncovered some people complaining of this problem with the Verizon iPhone 4 and it sounded like it was specifically a problem with the Verizon version. Does anyone else have this problem or know about it? Is there a way to fix the Verizon phone or do I need to try the AT&T version?

iPhone 4, iOS 5

Posted on Oct 18, 2011 10:24 AM

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Posted on Oct 18, 2011 10:53 AM

I have a VZW iPhone4; this is actually my second one because the first was replaced by Apple under warranty for an unrelated hardware problem. I use Runkeeper a lot, for man different activities, and in general I find the iPhone's GPS very, very accurate - not at all like your results. As a diagnostic step, you might try temporarily using another app, like Runkeeper or Nike+ to see whether your results improve. If they don't, it is possible that the GPS is malfunctioning - that's not unheard of. AFAIK there's nothing specific to the CDMA phone that affeccts GPS performance.

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Oct 18, 2011 10:53 AM in response to frogman470

I have a VZW iPhone4; this is actually my second one because the first was replaced by Apple under warranty for an unrelated hardware problem. I use Runkeeper a lot, for man different activities, and in general I find the iPhone's GPS very, very accurate - not at all like your results. As a diagnostic step, you might try temporarily using another app, like Runkeeper or Nike+ to see whether your results improve. If they don't, it is possible that the GPS is malfunctioning - that's not unheard of. AFAIK there's nothing specific to the CDMA phone that affeccts GPS performance.

Oct 19, 2011 6:26 PM in response to frogman470

Just an update for anyone who might be researching a similar problem. I tried it with RunKeeper. It was more accurate, but still very wobbly. Compared to the routes I tracked with my Evo earlier this year, it just doesn't compare. When I doubled back on my route with the Evo, rarely were there any gaps between my paths in both directions. And when there were gaps, they were tiny. But with this iPhone 4S there are nothing but gaps between the paths. So maybe it's the phone. I'll take it to Apple to see what they have to say.

Oct 24, 2011 11:50 AM in response to frogman470

Thought I'd add some more info on the general question. I may post this in a separate thread, too, to try to figure out whether the results below indicate that one or the other of the phones involved is defective.


I did my usual weekend walks in the local conservation land this weekend. I took both my iPhone4 and the new iPhone4S with the idea of comparing their GPS performance. The short version is that they are reporting very different results.


The iPhone4 reported 6.52 and 6.54 miles on the two days (which is remarkably consistent). The iPhone4S reported 6.26 and 6.09 miles on the two days, which is a lot shorter (especially the second day's results) and less consistent.* Both phones are running iOS5 with hardware settings and software installations that are as identical as possible, and both were running the same software (Kinetic GPS) with the same options selected.


*On Saturday, I was streaming a local FM radio station on the 4S, so some kind of RFI or other issue between the 3G radio and the GPS receiver is probably a possibility.


Looking at the GPS tracks on a map, it's hard to draw any useful conclusions. There are no points that are significantly out of any of the tracks. In general, I tend to think that the tracks recorded by the iPhone4S may be a little tighter when you compare sections where I walked more than once (and therefore in theory the tracks should be identical, but never are with GPS for many reasons). However, there are sections where the 4 was plotting a tighter track than the 4S, so it's hard to say, judging purely by eyeball.


I am a little puzzled...wondering whether one or the other has a defective GPS chipset, or whether there's another explanation? Theories are definitely welcome.

Verizon iPhone 4S: Problem with inaccurate GPS tracking

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