Elevation profile during an activity shows large and implausible variation

Hello Garmin users,

I have a problem with the elevation profile recorded during an activity.

The elevation profile, usually tracked during a bike activity, shows large local variation, jumping by about +-30 ms at every measurement.

At the start of the activity the elevation is correct +- 5m and also reliable when not in an activity; it also looked fine in the bus, but I did not try for longer then 5 minutes yet.

However, when moving forward on the bike the jumps in height are up to 30 meters in 3 seconds.

The behavior appears to start after about 15 minutes. Before that time the track looks smooth, sometimes even parts of the track show a smooth elevation.

Overall the behavior is surprising, it never occurred before April and without a software update taking place at the time.

Yet, the problem appears to be a software one -- using a DTM/DEM to re-project onto or simple smoothing should deliver much better results.

Why would the sensor turn from accurate in the beginning to large variation for the next 50 minutes, then work again for 10 minutes (at least no jumping) and afterwards go crazy for the rest of the tour.

Interestingly, it is much more accurate when climbing and worst on straight terrain.

I have added two examples below, the first on flat the second on more hilly terrain, which is more accurate, at least uphill.

Thanks for your input.

  • I answer by myself:

    One can enable the elevation correction in Garmin connect on the web, which apparently uses a DTM/DEM.
    However, the profile recorded by the watch by the watch should also be accurate .. so still happy about possible solutions/comments.

  • Have you checked the calibration settings for your altimeter on the watch? There is an "Auto Cal." setting that you can set for "During Activity: Continuous." I believe this will continuously calibrate the elevation to DEM via your GPS location throughout the activity. Now, how often "continuous" is, I'm not sure, but you'll still see minor elevation changes due to the barometer. But, tying the elevation to DEM is supposed to eliminate those random, large jumps that can occur from barometric readings.

  • Thanks for the reply.

    I indeed tested all the settings that are possible here. None of those solved the problem.
    Maybe I am just sweating too much :).

  • How does the elevation profile look like when you disable the auto calibration during activity? I wonder if these flattened areas are from the DEM data, and the spikes are from the actual Barometer readings... If this is the case, disabling the Auto Calibration during activity should leave you with only spikes, without any of the flat sections. Then this would mean there is an issue with the barometer sensor. If they are still there, then..... I don't know ;-)