Wonderful, thank you David! Do you know why it is not “working” on some activities such as Intervals.icu?
the values are shown if I manually select an interval, but it is not appearing on intervals set on the activity, only “w” is shown, without any value.
Edit: It seems to be solved 
Yes you need to make a small edit to one of your intervals (or add one) to get the rest to be re-analyzed.
Hi David,
Is it possible to add a field (maybe customized) to know the equivalent average power not only at the sea level but instead at a specific altitude in meters? (based on the % of power at the sea level and Bassett formula)
Would be useful to know how much power could be estimated for an event or race at a specific altitude or for indoor activities when we travel to different altitude place…
Thanks a lot!
Fabian.
I think that will need to wait until custom fields are implemented. I am not sure how to fit it into the UI.
Sorry for using necromancy on an oooold thread, but I just discovered intervals.icu (amazing work here, truly! but you know that) and had one question related to altitude estimates. I’m at 2500m/8500ft normally but I ride in Zwift which provides virtual altitudes that have no bearing on my reality of course. So altitude adjustment for these workouts is desired but not possible.
Would it be possible to say for a ride “this ride was virtual and was conducted at 2500m, use that for altitude adjusted power estimation”. Or even to have a profile setting where you could say “I’m at 2500m, use that for all virtual rides”? Then of course I guess you’d want that to be set over time periods so if you travel you could move it (I could dream up features all day ;-). The MVP would be to just set it directly in a virtual activity though, for me.
Even if the idea is a non-starter, really impressed by the site. Cheers
Makes sense.
If David doesn’t implement this directly then it will still be possible in the upcoming custom activity charts feature and should be pretty easy to implement as it’s just multiplying the power stream by a constant.
That would certainly bring things closer (and in fact, as a sometimes-lazy programmer myself I’m tempted to argue it’s “good enough” really) but if you go up the Alpe du Zwift then you’ll get 9500m elevation or so at the top which isn’t correct either as in reality the activity is at an unvarying altitude the entire time.
I’ll keep my eye out for custom activity charts though - thank you!
I have added altitude to Actions → Fix Data under the activity timeline chart. You can use this to adjust the altitude trace.
Well that did the trick perfectly! Thank you very much. You’ve more than earned my support, I’ll go set that up to make sure I buy you a coffee equivalent irl
Sorry for another necro - thank you for this chart option! It really simplifies activity comparisons. Would it be possible to extend altitude-adjusted power to the Power/Duration curve, and the “Compare” charts like Power vs HR?
I’m about to move to a location that’s 5000 feet higher than where I’ve trained the past three years. Even after acclimatizing, the ~5% hit to FTP will make it difficult to directly compare my progression to past years’ numbers.
I also foresee hitting power-related PRs when then traveling to race at sea level, which would have the same effect of muddying comparisons.
Hey Nick - I’ve asked for exactly this thing here Fitness Charts using alternative W, specifically based on W:alt
…for exactly the reasons you mention, except my altitude hit is around ~15%! (2500m to sea level) and it makes my charts pretty difficult to interpret that’s for sure
That’s a good idea but quite tricky to get done. The power-duration and other related curves (power vs HR) are computed for each activity and stored. So I need to store a whole new set of altitude adjusted curves. I have added this to the todo list.
One thing maybe worth noting is that the actions->fix data->altitude offset change is always applied after activity initial processing so the ability to reprocess whatever is precomputed, ideally in a batch would be great. I can theory craft features for others to implement all day long tho of course. Thanks for even considering this
Ah, I had hoped it could be applied as a layer between the source activities and the PD curve. But that does sound more involved.
Somewhat related, it’s amazing how performant intervals.icu is with all the data it handles!
Thanks for the consideration David!
I know this probably isn’t the intended use of this feature (also googling and searching the forms I havnt found anything) – but I am going to be at 7k feet/ 2100m the next month or so and wondering if there is a way I can override the altitude from zwift to use something like this so I can compare to my otherrides while I am back at sealevel?
You should be able to use this feature to adjust the Zwift altitude. Also you can now filter for activities by altitude:
Where/how do I do this?
Fields are available:
A couple charts, at the bottom of activity click on Charts
then at the bottom of the pop-up ^^ click on chart search
and you’ll find some pre-made charts.
Here is an HC climb where I removed the line for adjust power acclimatized:
You can make your own with the fields available.
Hope that helps.
Thanks, that will do. Odd that these didn’t show up yesterday when I searched for altitude
