There is a fair bit of information out there on Nike+ calibration. The official documentation doubts it is necessary for most people. But I have seen some people post on the internet that the default settings can be off by 10%. 10% is a huge number.
I decided to calibrate from the get go. I had the chance to go for my first run tonight with my Nike+ gear. To make it a calibration test, I drove over to the high school track so I could carefully measure the distance.
Note: I have followed up this blog entry with a post on calibration best practices gleaned from my experience.
My First Calibration Run
I carefully read the instructions on how to do a calibration. After a couple of false starts, I got under way. I decided to do a 4800m run (not quite 3 miles) to give it plenty of time to get to know me.
I huffed and puffed (more on this in a later post) my way around the track. It got dark in the middle of it, but I had enough visibility to stay in lane 1. To get as accurate a read as possible, stay down the middle of lane 1 because that is what is measured at 400m. At the end of the run, I held the button for 3+ seconds to stop the read. So far so good.
I was excited to get home and see what my stats were. I uploaded my results by inserting the USB device into my computer. I also made sure to change units to kilometers in the utility (see my blog post on how to do that) since I had measured my run in kilometers/meters and not miles.
Unfortunately, after I uploaded my run, I am now left with a bit of a puzzle. Its not hard to keep track of 12 laps. 12 laps x 400m is 4800m. I expected the Nike+ device to be somewhere near that. Instead, it thinks I ran just 4410m. Wow, off by 390m, which is about 10%, just like other posters on the internet said.
But wait. A single lap is 400m. Is the device off by 10% or did I miscount my laps? Perhaps I ran only 4400m, and therefore the device is only 10m off (.25%). Grrrrr. Self doubt. Second guessing. Etc Etc.
My Calibration Conclusion
I believe the device was off by 10%. The reason is this: I was incredibly slow for a 4800m run. I was impossibly slow if I ran only 4400m. Or at least that is the story I am sticking to for now. I recalibrated the device based on the assumption that I ran 4800m.
To put this doubt to rest, I will return to the track a few more times to make sure the device is calibrated properly.
Update: see my follow up blog entry that reveals the answer to this puzzle.
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