Holy s**t, John, you sure know how to get emotional about a power meter. My apologies, straight-off, for defending something you seem bent on discrediting ... again, I repeat, without data
For the record I don't work for their company or have any affiliation with them. I may sell them at some future date, but that depends upon a. their testing providing good results and b. my testing providing good results. I don't want to sell an item I don't think is worth buying.
I don't know why disagreements on message boards always have to get personal. If you
have some affiliation with Polar and I am thereby insulting you by expressing my dissatisfaction with it, I apologize.
As for the rest:
As for the wattage community at large, "learned" is a great thing, but there are a great many learned people out there who get things wrong, especially when they make judgments on an entirely new paradigm without the benefit of data. This is not meant to be insulting, it's a fact that anyone who is sufficiently learned to be listened to should readily admit.
The whole lot? Please. In the Wattage Forum, not a single sports scientist or trainer of note has been impressed with this product. These people are smart, learned and experienced enough to comprehend the underlying concept and are not impressed, other than the iBike Pro simply being a more advanced Cyclosport. Current discussion of this product is NIL. That says it all.
Now "credentialed," on the other hand ... I find credentialed to be a highly overrated measure of someone's competence.
Such commentary does not reflect well of you.
I stand by my statements, and I find it unfortunate that you can make a judgement of me because I am not impressed by credentials. I find it even more so that you would malign my character because I don't believe in credibility by diploma?!
The first statement above is simply true and is not intended to be denigrating to anyone. A learned person should not make categorical statements without something to back themselves up, though in my work I see it happen very frequently. I review a lot of papers that make this mistake, and it's frustrating to see such things appear in the peer-reviewed literature regardless. Since a wattage forum is anything but peer-reviewed, its results are bound to be that much worse. Sorry. And no, I don't consider a coach qualified to make a judgement on something he cannot compare to anything currently in existence! I wouldn't even trust a scientist to make such a statement.
The second statement has two facets. One: a message board is a convenient place to make up credentials. Who could or would check? And two: I prefer to listen to people who rely more upon their work than their credentials, eg. "I graduated summa cum laude from Harvard" means a lot less to me than "I investigated the relationship between power output and nutritition in 250 athletes who participated in a study for a period of two years."
Since you're so bent on credentials, I might as well tell you I have a PhD in physics and currently work as a research scientist, with a joint appointment at the CIRES Institute at the University of Colorado in Boulder and Colorado Research Associates. My personal webpage is here
, if you want something to back that up. You'll note that I'm actually relatively well-qualified to discuss this topic.
Please note that I am only one of two people who post on this account.
The iBike Pro appears to employ a venturi anemometer to measure windspeed. These devices are affected by both barometric pressure and wind direction.
My mistake. But my main point was that the barometric pressure sensor is independent of the anemometer and therefore the iBike does not have to rely upon a constant barometric pressure - it can adjust for it on the fly, at least in principle.
Except for? This is the underlying problem with the iBike and the reason its not a powermeter. IT IS A POWER ESTIMATOR. Go play with analyticcycling.com and see what "estimating" CdA does...
The question you aren't asking is what the error is in the CdA. I know exactly what changing CdA does, what I don't know is what the measurement error associated with this is. And calling it a "power estimator" is pure semantics.
If you don't consider the iBike to be a true power meter, then I would honestly like to hear your definition of the term.
SRM, Powertap, Ergomo, Polar.
Haha so because this is not an SRM, Powertap, Ergomo, or Polar, it is not a power meter. Very good. If this is your definition, I cannot help but agree, since iBike is definitely not any of these.
I would define powermeter somewhat differently. Perhaps this is the source of our semantic difficulties!
The measures employed by the major PMs are very much *not* direct, they rely on piezoelectric currents
Doesn't the iBike's accelerometer depend upon a piezoelectric (resistive) sensor? Probably the most accurate thing it does too.
Not only that, but their solution for measuring altitude gain (and therefore slope) is based on barometric pressure...
Dissing Polar again. Doesn't iBike use the same method via its barometric pressure port?
No. It uses the accelerometer you mentioned above. Polar relies upon barometric pressure for estimating hill slope, and the outcome can vary quite widely.
iBike Pro's ESTIMATION of power is dynamically affected by any of the following:
1) Change in position
2) Change in weight
3) Change in tires or road surface
4) Change in barometric pressure (in vortex chamber) due to a front, elevation, or temperature change.
6) It does not include a heart rate monitoring function, this must be factored into the value (and weight) equation.
Here you have shown why this argument is occurring, and in #5 I suspect I see why iBike is not well-liked on the wattage forum.
#2 is a fairly unusual thing to change by any significant amount during a single ride. Certainly even a water bottle's difference shouldn't change things dramatically.
The reason #4 is not an issue is listed above, so I won't go into it further.
#5 is a misstatement and exactly the sort of misunderstanding that could be iBike's biggest problem: of course iBike's readout is affected by drafting (if you think for a moment, you'll realize a PT is affected in exactly the same way ...)!
That leaves #1, #3, and #6. #1 I will agree is an issue - I just don't know to what degree (and I don't plan to make a judgement prior to getting data on it). #3 could also be an issue, though I suspect not a big one. #6 is a marketing problem, but you can get a cheap HR monitor (~$30 on eBay) separately if it's that important to you.
As such, iBike Pro is not only inaccurate, but non-repeatable. Repeatability actually being a more important factor than absolute accuracy.
This statement cannot be backed up and IMO you shouldn't be making it without data. Replace "is" with "seems to me to be" and we're fine.
If iBike sucks, I will be selling mine off pretty quick. Again, I'll let you know when it comes out.