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?
Best Answer
My experience helping others with this problem seems to suggest a few things:
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.