In an effort to determine just how accurate my Nike+ iPod is and how it compares to GPS based mobile applications I decided to test both of them out in a very controlled environment.  I ran with both devices the same distance- exactly one mile around a track.  Then I compared the results of each device- and both were off, but the GPS was off by a lot.

First off, note that I have my Nike+ calibrated to my stride already (which I used a track to set) and I ran a comfortable pace for the mile so I was not pushing it too hard or too little, a standard stride in other words.

The Nike+ showed that I ran .97 of a mile, so off by 3%, which seems like a very reasonable margin of error.  I suspect that this has to do with the placement of the chip which I tuck under my laces, I do not run in Nike shoes with the special slot.  See the graph below:

It is interesting to note that the speeds vary dramatically as reported by the data- as fast as 6:19 per mile and as slow as a 7:53 per mile pace.  I think this range is much too large for a 4 laps on a track at an even pace, though I am unsure why the variance would be so large. As a side note I mapped this track with a couple different online tools like MapMyRun and Runstoppable and both accurately measured the track.

However, using WorkSmart Lab’s CardioTrainer for my Android based phone was much less accurate (I have a Motorola Droid on Verizon).  I set the GPS ping time to 1 second and wore it in a clear sleeve on my arm.  The track I ran had no tree coverage or other interference for a clear satellite signal.  As you can see from the image below it’s very off from the track (which I ran the inside most lap). Also of note is that I ran 4 laps on the track- the app was consistently off in the same way much of the time. There doesn’t seem to be any conclusion to draw about which movements are hardest to track (longitude vs latitude).

As well you can see from the image below for whatever reason the elevation is very off (this is a flat track) and the speed variance is very large as well.

So the summary conclusion is that Nike+ iPod is the most accurate for total distance even with a number of oddities to the data (I hear calibration is key) and WorkSmart Lab’s Cardio Trainer is not very accurate at all, but if you are running somewhere new or someplace you don’t know (like trails) it can be a great way to find out where you went.  It’s a nifty app for sure, but I wouldn’t rely on it for data that is more than directionally correct and would certainly never run splits or time trials with it.

Next on the list to check:
*Nike+ on a treadmill
*Other GPS Android run apps to see if it is CarioTrainer or phone hardware.

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