The GPS Conundrum

20130817-133433.jpgIt drives me a little nuts that when I use both my Garmin Forerunner watch and my mapmyrun app on my iPhone to track a run, they come out with different measurements. Usually by a lot.

I tend to go with the Garmin for accuracy, but I’m still puzzled by the discrepancy. For instance, today I ran either 14.02 miles or 14.69 miles. A 9:30 pace or a 9:15 pace.

I mapped out my run ahead of time using mapmyrun. Presumably it would have accurate road measurements. I guess I understand when it might ping off the satellite funny during a workout, whether it’s weather related or a bird flies by or trees get in the way. But when it’s using a map, I don’t get why it would be off. According to my initial course and the final mapmyrun readout, I hit 14 miles at the same place. I did five loops around a lake, and I’m guessing it measured it the same distance each loop.

I know this is a common problem between devices and that the majority of people go with the less favorable Garmin measurements. I just wish I ran faster, I guess.

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10 thoughts on “The GPS Conundrum

    • I think the GPS in the iPhone is somehow slightly off. Not sure why. But consensus seems to say the Garmin is better. I was really shocked that the difference this last run was 7/10 of a mile. That’s a pretty big variance.

      You might want to try using your Garmin and your Nike+ simultaneously once and see the difference. It mostly matters if you use the pacing in a race and don’t want to miss your goal time because of the inaccuracy.

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