Does this mean ErgZone is sampling more often than ErgData?
Well, to answer my own question from my previous post as to what the Athletica A.I. would do with my 7-weeks of corrected (replaced) STRAVA direct-imported rowing data, attached is the answer I received when I first logged-in this morning to verify today’s workout (I added the Pace conversions in BLUE rounded to the nearest 0:01).
While the Power (W) changes appear slightly significant, the changes to the respective Pace targets are roughly only 1-sec. In the real workout world when erg rowing at those paces, a 1-sec differential isn’t worth trying to hit even though the math would say it’s a 4th power difference in effort🧐. Given that math, I’m just glad the changes in Power weren’t any greater🤓
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Okay - this is interesting. If I download the fit file for a row from ErgZone and examine, I see data recorded at 1s intervals. However, if I download the same row from logbook I see data recorded at 3s intervals. So, C2 is applying some sort of compression? Why would they be doing this?
Your question has been asked elsewhere, but no firm answer. Concept 2 Data Recording Interval - Intervals.icu Forum
My recollection from various readings is it has to do with the erg’s mechanics of how the sensors collect, and the controller processes/transmits, the data.
Someone with a lot more knowledge than me will have to chime in
I sent both C2 support and Ergzone an email. Either ErgZone is interpolating data, or C2 is doing some sort of compression. I actually posted in the Intervals thread about this as well. I’ll reply in both forums when I get a response.
Per ErgZone support:
- C2 Logbook expects data per stroke, so this is what is sent by ErgZone to Logbook.
- The reason the fit file export from ErgZone Admin is on a per second basis is because this is what is expected by Garmin.
- ErgZone actually captures data 2x per second.
Makes sense now.
[note: Not sure now why I spent so much time looking at this. I suppose it’s because I didn’t want to do any actual work because I was tired after a longer run today. I am sure there are some very simple answers to these questions and will be shown so. I was hoping that I might chance upon one, but seem to have failed.]
You already know this, but the obvious challenge with measuring pace in rowing is that the data are highly cyclical about 2-3-ish second intervals. So instant pace will always be squirrelly. Pace values are in the logs, however, so one wonders at which point of the stroke (which lasts > 1 sec) pace is measured. The API docs show HI/AVG/LO values are available.
From C2’s “PM5 Communication Specification”, the monitor calculates and shows the pace, but the pace seems not to be sent to the logbook, which actually stores at 1-second intervals (from page 104):
Nonetheless, the C2 .fit file contains an “enhanced speed” field, recorded as m/s (so maybe the logbook calcs the speed and ships it in the file):
EDIT: I just looked again at the C2 file and the intervals begin to vary between 2 and 3 seconds as the rate increases. So I am guessing C2 records a value for each stroke and records that value for each stroke and that the .fit file provides that stroke-by-stroke recording.
ErgZone .fit has the same field. I first thought that all data but HR and distance were na.locf (R ref for @Fazel) across the 3-second intervals:
But at higher stroke rates, series suggest otherwise:
So maybe outside of HR (provided to the monitor from another source) and distance, the data points are calculated on a per-stroke basis and recorded at 1-sec increments as whatever value they happen to be at the time. there’s a threshold, then (from 20 SPM to 21 SPM), where the data will bump up in frequency, given the stroke rate crosses the 3-second barrier.
EDIT: Seems the C2 file does this, too. IT just doesn’t fill in the per-second spots between strokes.
From ErgZone data, we can chart a “simple” pace (diff on distance = m/s), unsurprisingly offering up the messy values. A platform can choose to plot the available data, or perhaps calculate their own pace series (I assume the Athletica folks may chime in with any math they are applying).
All that said…I could not replicate the ErgZone or C2 pace data (And I have not idea what’s happening to the Garmin data).
Side thread:
Discussion on what the PM calculates and can send via BT:
https://www.c2forum.com/viewtopic.php?f=10&t=208908
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