Nike speed distance moniter

Sorry Phil,
The SDM IS a pedometer, a refined one I'll admit, but only a pedometer. It uses the same methodology as a pedometer to estimate the basic stride length and then corrects this with inclination measurements to take hills into account.

The 97% accuracy claim is completely false, there is no data to back this claim up. Given the measurment methodology it is in fact impossible to prove this claim as it depends on too many uncontrollable factors.
It may have given a distance close to the true distance on a few occasions but on how many occasions has it been way out?

An SDM estimates, a GPS measures. The difference is that simple.

Be careful about saying "an SDM". The Timex calls itself an SDM, even though it's a GPS.

SDM ="Speed and Distance Monitor". Says nothing about the technolgy being used.

Outsider - have you owned a Nike SDM? After 40min calibrating on a local 10k course, its never been more than 0.5miles out over 10miles.

On the GPS thread somebody measured 2.5miles when it was infact 3.5miles.

You say there is no data to back up the accuracy of the Nike unit? Why not ask the owners. I'm sure some will hate it and some will love it.

"On the GPS thread somebody measured 2.5miles when it was in fact 3.5miles"

Phil, I think that must have been user error, or some confusion about how GPS works. If you ran through a tunnel for a mile, then turned and ran back again, the GPS would think you hadn't moved. If you ran through a tunnel for a mile then emerged from the other end, the GPS would work out from the before and after position that you had run a mile.

It's a question of fitting the technology to your needs. For me, the GPS works very well. For people who run through mazy tunnels or (perhaps) alongside very tall buildings, it may not be reliable.

But in normal use in open sky, you would never get a discrepancy of a mile like that. My basic round-the-block run is ALWAYS 3.51 or 3.52 miles. There's no more variance than that, and I must have run it 80 times since I had my GPS. That amounts to 15 metres or so in 3.5 miles, which can probably be explained by minor differences between each run in any case.

I've no doubt whatsoever that the circumstances of some runners will cause GPS problems, but let's not dismiss the entire technology on that basis, especially when the gerat majority of us are happy with it.

Andy

HAs anyone actually done the same run with the Nike, Timex and Forerunner and see what the difference is?

Who's dismissing GPS???

I spent the whole of Saturday afternoon sulking because I'd just spent £168.50 on clothes instead of a GF... (Admittedly it was through years of under-investment in my wardrobe that forced me into the sitation)

I'm desperate to own a GF - but I find the Nike's just good to bin. People are slagging off the Nike, probably with no ownership experience and its not fair.

This thread was originally started by a guy looking to spend £100 or less, and for £60-70ish, the Nike is a brilliant tool.

Trust me, if the Nike goes pop or the GF comes down a tad, or even if my will just capitulates, I'll be a GF owner in the future.

Phil,

The magnitudes that the Nike SDM is measuring have no direct mathematical relation with a particular persons stride distance, it is a pure estimation based on the "calibration". Therefore, from a metrology point of view, it is impossible to state any sort of relative or absolute accuracy for such a device.

The owners of a measurement device should not have to back up a manufacturers claims. It should be the manufacturer.

What I have stated is a matter of fact, not a subjective argument.

I'm not saying that the Nike SDM isn't an adequate device for some, but everybody should be aware of exactly what it is before they buy one. Nike aren't at all keen to publicise (admit?) exactly how their SDM works.

Outsider -

Do you understand the technology? I see zero relation to a 'glorified pedometer'.

Have you experience with using accelerometers for measuring velocity? If so you'll see that there is a very clear mathmatical relation, and the technology does not rely on a persons stride length. The calibration is that of the transducer - not of the stride length.

Ironman - glad somebody else understands how an SDM works.

Outsider - you say "The 97% accuracy claim is completely false, there is no data to back this claim up. Given the measurment methodology it is in fact impossible to prove this claim as it depends on too many uncontrollable factors." so I gave you data to back this up; why are these not acceptable??? Do you need to see someone from Nike running in one?

""After 40min calibrating on a local 10k course, its never been more than 0.5miles out over 10miles."

Erm, isnt that 5% error then ? So outside the 97% accuracy - in fact almost double it ?

I own a Nike SDM. Decided to because I was running mainly in a town and thought GPS might be a problem. I have found a few things (I have been using it since Jan)

Once I worked out how to calibrate it the distance measurement seems accurate. Of course I cannot measure how accuate as I have nothing to compare it to. I also use gmap pedometer to measure routes, the widely held view is this slightly ups the distance and my SDM is slightly under the gmap distance.

I wouldn't get a Nike SDM if you don't live near a track, I have had to calibrate it three times since Jan (fortunately I live 1 mile from a 400m track). Once when I bought a new pair of shoes the calibration was obviously way out and once when it seem to just clear everything for no reason (and the battery hadn't gone flat). Note: keep a note of your offset value in case this happens.

Nike do say it isn't accurate if you aren't an evenly pace runner, which presumable most aren't. At the moment the Nike is good enough for me. I am training for the FLM and don't want to shell out another £100+ for a GPS that may or may not be better.

Hope this helps.