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Glitchy footpod data. Help?

William JenksWilliam Jenks
in General Training Discussions
This concerns using the Garmin footpad with a watch pickup, in my case Garmin 910xt. It is about strictly indoor running with the GPS OFF.

Recently, I've started getting these odd glitches where the system thinks I am going crazy fast for a few seconds. I can't figure out what sets it off and their appearance is irregular. It's enough of a problem that when it is happening, the miles are somewhere between 5-10% too fast or too short because of these "fake" fast spots. It's NOT a calibration problem. I know my normal calibration number, and it goes back to that unless the glitches happen during a calibration run.

This link below is to an 800 m run that was supposed to recalibrate the thing...and the calibration this set was too small by about 5%...because the glitches were in there:

http://connect.garmin.com/activity/269488381 Notice the spikes in the pace graph.

I have changed the battery in the footpod and it didn't fix it. The footpod is almost exactly two years old.

I don't mind replacing the footpod if this is the obvious first sign of failure, but I don't want to drop $50 for no reason, either. Any ideas?

Thanks!

Comments

  • tim cronktim cronk
    http://connect.garmin.com/activity/270296711

    William I get the same thing with my footpod(brand new) although the spikes are so short they dont really effect the overall data. I don' know what to suggest but wanted to let you know I'm sure others are experiencing it. I calibrated mine once on the TM and its been pretty accurate with distance and pace relative to the TM data. I have much more issue with the garmin HR straps which eventually turn erratic (different recent thread rant)!
  • William JenksWilliam Jenks
    Tim-

    Thanks for letting me know.

    This is a new problem for me that really only popped up in the last few weeks. I've used this (or the previous generation) footpod without significant incident for maybe 5 years. This is the first time when any data glitches got big enough to make a difference. The spikes shown in that data set are typical of this new problem and are enough to make the footpod useless for indoor pacing if it continues.... Being accurate to a random ~5% means +/- 20 sec/mile, which is pretty huge! :-)

    The problem is that you can't "calibrate out" random spikes. If it were a non-random thing, it would come out in the wash when you did a calibration.

    I'm hoping that it just means the accelerometer is breaking down and replacing it will fix it. That would be a little disappointing but quite easy to deal with.

    During The Interregnum, I posted a version of this question on ST...a couple thoughtful replies (including one who sent me to Garmin support), but no real answers.
  • Steve WestSteve West
    @ William, just a long shot but can the FP bounce on the laces from time to time causing the doubling the stride count?
  • William JenksWilliam Jenks
    Good question Steve -

    If that were the case, you'd expect a corresponding spike in the cadence data and speed/pace data, which is not seen. However, it's possible that the two are averaged so differently that the cadence spike doesn't show up. This would be the case if cadence data are averaged for 30 seconds or something.

    Nonetheless, I the other day, I did put the clip over a third lace loop to tighten it down to the shoe further. I've only run once since and didn't have any glitches...but that is not a good sample size yet, since I know they come and go.
  • William JenksWilliam Jenks
    I did contact Garmin support. They suggest taking the battery out for a long time (5 min or more) to let the footpad "reset". I'll give it a try. If no more glitches for a week, it's probably fixed.
  • Joseph LombardiJoseph Lombardi
    Well the only thing I will add is some thinking....as the GPS is off...and the only data transfer/pickup is really accelerometer based cadence and the speed/pace is a calculation (based on cadence and stride length)......then it may be some sort of adjustment the data is making to account for a disruption in the cadence data stream from the footpod......

    While I don't have a solution and hope your reset works (will be interesting)...my thought would be...a. Does it really matter? ie. if you didn't see it graphically represented would you dispute the run results?

    (to Tim's point...I don't believe/and it doesn't appear based on your graph...that the spikes have an impact on the overall run data/speed/pace calculations)

    b.) I have a footpod and have been interested to see my cadence v. pace v hr on outside runs...but have concluded that using the footpod for trying to fine tune runs indoors is a waste of time...for me anyway....too many varialbels (you change your stride on TM etc.) so when I have to run indoors I will just try to use the same TM @ my gym..and if I'm on the road on biz....I'll just live with what exists....its not enough times to matter to my training in the long run...
  • William JenksWilliam Jenks
    @JL - the reason it "matters" is that I like to run my intervals on unmarked courses a fair amount of the time, and the spikes are enough to throw off the pace significantly. A 5% error at 7 min miles is 25 sec/mile. So I can think I am running much faster than I am....as I like to use the "lap pace" average with a 1-mile auto distance when I'm running on unmarked distances indoors. (This smooths out the data noise and also gets rid of the artifacts that you get from hard cornering on a track.)

    Anyway, we'll see...I ran outdoors today.
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