Cycling Power Estimator

The Lost Alien

@mickywickyftw Thank you for your time, I will give it a try when I get home and keep you informed.

The Lost Alien

@mickywickyftw Excellent, it’s working perfectly now, and the cadence RPM is showing correctly as it should. Great job!

mickywickyftw

I’ve introduced a new setting for user weight. While reading from the watch user weight value appeared to work, it was causing issues when starting the SuuntoPlus app with any non-default rider position.

SergioB

@mickywickyftw thank for the app! I’m kinda new to cycling, I’ll test next ride

I have a question: the FTP value requested as input in the Suunto App is used for the power calculation or it necessary for other scopes?
Haven’t dove any FTP test yet, so if needed for the power calculation I would set a guessed (aka random) FTP

bubuche

I noticed that there is something wrong in descents. The power is sometimes overestimated. In the screenshot below, I reached 450W ; speed is high, but I was not forcing at all. Note that I have no cadence sensor. I never observed such errors in ascents.

mickywickyftw

@SergioB Not, it’s only used for the power zone gauge.
So if you have no idea of your FTP it doesn’t affect the estimates.

mickywickyftw

@bubuche There is a grade lag at the start of a descent due to smoothing. So the calculation uses the previous flat section (0% grade) until the smoothing catches up. And even then you might be at -8% but the calculation uses for ex. -2%. At this speed, you are going above the assumed terminal velocity (which is too low), and get high power spikes,

Without a cadence sensor, I could zero the power when going downhill and avoid these short spikes.

So replace a false positive (what you see) with a false negative.
I guess the false positive is the worse issue since it impacts NP, averages, etc.

So this needs fixing, but without breaking other cases. I’ll have a think.

bubuche

I should maybe raise the average window from 3 to 10s, to smooth that grade variation (especially in descents).
My guess is that 0 is probably closer to the real value than 450W (at + 5/7% grade, I am between 200 and 350W). I agree, you probably won’t get heuristics that works in all cases.

mickywickyftw

@bubuche Check with the latest update, I’ve re-done the logic.
Now if there is no cadence sensor, power is always computed on the difference between actual speed and terminal velocity.
Terminal velocity is still subject to grade smoothing. The altimeter looks at altitude in 20cm chunks apparently, so you need several metres to compute a useful grade reliably.

This is computationally more expensive but may not make much difference overall.
I’m just hoping for no unexpected regressions.

bubuche

@mickywickyftw thanks for the update, I’ll try this week hopefully (on the same road, to compare).
One suggestion could be to wait for a few more seconds when the slope reduces before using standard formula (I totally ignore if there are mathematics models behind this, just intuition and probably hard to calibrate). I mean we are still fast for a while when the grade drops from -4% to -2% for example.