New toy for Floyd

Personally, I like not having any detrimental reliance on outside
technologies. GPS not withstanding, a HAC4 provides as complete
information if not as "absolute" as GPS coordinates. I think the
PowerTap data gain from the association with GPS' absolute qualities.

That help...?

-r

Bob Schwartz said:

http://www.uwalumni.com/onwisconsin/2005_summer/Research.pdf

A PowerTap with a GPS.

After reading the article I'm not sure I get the point. You
should be able to compute what the GPS gives you from the
PowerTap alone. Maybe it makes mapping the data easier.

How to turn an expensive power meter into a cheap altimeter:
http://anonymous.coward.free.fr/wattage/altimeter/altimeter.html

Robert Chung said:

How to turn an expensive power meter into a cheap altimeter:
http://anonymous.coward.free.fr/wattage/altimeter/altimeter.html

Nice. Slightly related (2 clicks away): your rosetta page seems to be
missing.

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On 06/13/2005 11:19 PM, in article [email hidden], "Robert

Chung said:

Bob Schwartz said:

http://www.uwalumni.com/onwisconsin/2005_summer/Research.pdf

A PowerTap with a GPS.

After reading the article I'm not sure I get the point. You
should be able to compute what the GPS gives you from the
PowerTap alone. Maybe it makes mapping the data easier.

How to turn an expensive power meter into a cheap altimeter:
http://anonymous.coward.free.fr/wattage/altimeter/altimeter.html

So whatever happened to the full thing? Clicking the "Back to Home" link
(http://anonymous.coward.free.fr/wattage/index.html) hits a 404 file not
found error.

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Steven L. Sheffield said:

Quoted message said:

How to turn an expensive power meter into a cheap altimeter:
http://anonymous.coward.free.fr/wattage/altimeter/altimeter.html

So whatever happened to the full thing?

Thanks for the heads-up. Should work now.

Ewoud Dronkert said:

Robert Chung said:

How to turn an expensive power meter into a cheap altimeter:
http://anonymous.coward.free.fr/wattage/altimeter/altimeter.html

Nice. Slightly related (2 clicks away): your rosetta page seems to be
missing.

Yeah. I migrated a portion of the site over from its old location but not
all of it. I *think* you can find it now.

Dr. Sisyphus Frankenstein said:

Yes, it can be computed. Robert said: "The next time someone asks me
how good the HAC4 could be at measuring power, I'll say it's about as
good as using a powermeter to estimate altitude gain." GPS may be
cheaper than power meters at this point. So why the power meter instead
of just a GPS? "You should be able to compute what the PowerTap gives
you from the GPS alone."

The HAC4 measures altitude change with a barometer, which ought to be
much more accurate than altitude change from a GPS under typical riding
conditions - GPS is better at X,Y than elevation.

Of course, the altitude change only gives you an decent estimate of
power if you're riding up a moderately steep, long hill.

Ben
measures power with a multimeter

The good Dr. makes the point that computationally, we have left only
the argument where *best* do we obtain the data to derive power.

PowerTap is direct power with derived location mapped to contour.
Hac4 is direct contour with power derived from direct time/distance.

Hac4's are barometric sensitive, affecting degree of accuracy during
measurement. That same sensitivity provides resolution of gradient
changes w/in a reasonable window. I've watched 12% grades change to
16% w/in 20LF on-the-bike. It's near-realtime altimeter readings.

GPS I've raced with have varied, in one instance, we were unable to
locate the turning mark in one race. GPS can't match the resolution of
the Hac4 within 20 LF coordinates. The best GPS get your location
resolved to within 30-50'.

I share the good Dr.'s apprehension about the Hac4's power data. Hac4
computional algorythm is proprietary. I've not tested its accuracy
against a direct measure like the PowerTap.

In the end, I would choose Hac4 over GPS because Hac4 has better
resolution on-the-ground and leaves only the derivation of power
calculation in question.

Quoted message said:

In the end, I would choose Hac4 over GPS because Hac4 has better
resolution on-the-ground and leaves only the derivation of power
calculation in question.

How good could the HAC4 be at measuring power?
http://anonymous.coward.free.fr/wattage/altimeter/pseudohac4.html

Note that this is only the estimated best-case comparison. I have field
reports from HAC4 users that show large variability in power readings
while coasting downhill.