Isaac Power Calculation

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kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Isaac Power Calculation

Post by kq6up »

I wanted to do an experiment by trying to write a python script that would change the elevation data in a TCX file to known good elevation data from a LiDAR file. Does Isaac recalculate power when I swap out elevation while merging an .ibr ride with a .fit or .tcx file? I am interested in seeing how this affects my CdA calculations.

Thanks,
Chris Maness
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Isaac Power Calculation

Post by Velocomp »

No.
John Hamann
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Isaac Power Calculation

Post by kq6up »

So if I have ruled out errors from weight, Crr, and wind, the only thing that is left is slope. I notice the CdA readings go nuts when we hit rolling hills or otherwise not flat conditions. I can see fluctuations on my ride to the beach from CdA=.250-.350 that is a large fluctuation, and the data doesn't really seem to settle down. If one could replace the AP slope/elevation data after the fact and recalculate power and therefore CdA, that could be ruled out as a source of error. If correcting the elevation in the TCX file causes CdA to settle down that would make CdA tests more compelling. As it sits, I am unable to make small changes in equipment/positions come out of the noise. I only have some vague sense of large changes. Like wearing street clothes on my TT bike vs. a speed suit. I can definitely see a change, but that is because I go from .295 CdA to .350. The standard deviation at this point is just too broad to know for sure what direction the data is going for small changes -- they get swallowed in the noise.

This site can do it without a script:

http://www.gpsvisualizer.com/elevation

But changing the elevation/slope data without re-calculating the power in Isaac from scratch is of no use in figuring out the source of my data noise/fluctuations.

Thanks,
Chris Maness
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Isaac Power Calculation

Post by Velocomp »

Stand by for a firmware update.
John Hamann
kq6up
Posts: 57
Joined: Sun Jan 13, 2019 9:58 pm

Re: Isaac Power Calculation

Post by kq6up »

Velocomp wrote: Wed Feb 27, 2019 7:41 pm Stand by for a firmware update.
Sounds good. I am excited about the possibilities because the wind data seems really good.

Chris
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