iPod Nike+ Accuracy

Aragornii said:

For any of you Runners that use the new iPod nano with Nike+ built-in, how do you find the accuracy? For me, the accuracy is great for short runs and terrible for long runs.

Out of the box without calibration it measures my standard 4 mile run spot on to within +/- 0.05 miles, but when I run 8 miles it measures the distance as 9.2 miles.

Is it possible that when I run longer distance at a slower pace the calibration is off, as opposed to when I run short distance at a faster pace?

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I've had the same experience, I did an 8 mile run on Saturday and kept checking as I was running, it was spot on up until about 3 miles and ended up measuring about half a mile more by the end.

I calibrated after that run and my 6.5 mile run this morning was only over by about 0.1 of a mile. I'm going to keep calibrating and see how the accuracy improvesn (the manual states the more you calibrate the more accurate it will be).

my understanding is that it measures how many "footsteps" you take. Say every step I take is 1 meter. 1000 steps would be 1km. However, if I slow down, or virtually take smaller steps, like 0.90m per step, 1000 steps would realistically only be 900 meters, whereas Nike+ records I ran another 1km. (I speculating, but it seems they calculate based on "acceleration & time" on the timing chip in your shoe) As your pace / stride decreases in the latter of your runs, this is what I experienced.

There are two ways to run with the new iPod Nano software:

1) no Nike+ dongle attached: this simply uses the accelerometer movements to estimate your distance. It supposedly works best when clipped to the waistband of your shorts. Results will likely be a bit variable because the placement will be a bit different each time you run.

2) Nike+ dongle attached (with foot pod in/on your shoe): this uses an accelerometer in the foot pod which detects how long your foot is in contact with the ground. Using this information it can detect your stride length (and thus speed). I've found it to be very accurate but getting a perfect calibration can be a bit tricky.


Method #2 should almost always be more accurate (when calibrated properly) because it is directly on your foot BUT #1 can certainly work well if calibrated and worn in a consistent location/orientation.


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Article on Nike+ : http://www.wired.com/medtech/health/magazine/17-07/lbnp_nike?currentPage=all

The shoe sensor's accelerometer measures the amount of time a runner's foot is on the ground, which is inversely proportional to speed. Transmitting at 2.4 GHz, the sensor sends data to a receiver that's either attached to an iPod nano or built into the second-gen iPod touch

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Just so I'm clear...we still need the battery (the little capsule-looking thing with the red outline), but not the receiver (the little charger thing that clips into the bottom of the nano)? I did the software update but didn't realize that it now didn't need the receiver. Though I did want to check.

Everyone is correct. Any device that measures distance run by using an accelerator or foot pod is going to be somewhat inaccurate. Unless your gait and stride are the same at all times, you will never have perfectly accurate distances. Often times, your runs are calibrated by running 800 meters. For those of us who run multiple miles, an 800 meter run (half mile) is practically a sprint. My gait and stride tend to be completely different than if I go for a 6 mile jog on a Sunday morning.

In the end, I bought a GPS watch. You can get Garmin GPS watches for as little as $125 bucks (garmin 305) at Amazon.com. Your accuracy will be practically spot on as well as your speed and average pace, etc....

Edit: Garmin GPS watches generally allow you to use a foot pod as well for running in doors (i.e. on a treadmill like I will be this coming winter).