Altimeter and elevation issues still occurring (calibration & temperature)

Setttings

Forerunner 955 Solar (16.19)

Altimeter Settings:

-Auto Cal: On

-Sensor Mode: Auto

Issue

The elevation drifts upward during almost every run. For activities where I start and stop in the exact same point, the ending elevation almost always higher. I always calibrate the altimeter to the DEM right before each run. I previously contacted Garmin Support and they said to just try cleaning the watch more frequently. I have now been cleaning out the sensor port (as directed here) on a weekly basis and it still is an issue. These aren’t huge spikes in elevation, but they make me question the quality to the elevation data compared to other watches.

Temperature

I noticed that this issue is worse when the temperature of the watch drops during an activity. I confirmed this with a fridge test. After placing the watch in the fridge for 30min, the watch temperature dropped from 74F to 43F, and the elevation increased by 30ft. When I overlay the temperature graph on top of the elevation graph for my activities with elevation drift, the watch temperature usually decreases sharply in the first 15-30min and then stays the same for the remainder of the activity. I have also noticed this behavior without recording activities. If I go for a short out/back walk and calibrate the elevation at the start and then monitor the altimeter widget during the walk, the elevation is usually higher on the way back as the watch temperature decreases.

Comparison to Fenix

I understand that environmental factors affect the altimeter, but I have seen other watches perform a lot better. For example, during a recent 12 hour run I calibrated the start elevation at 520ft using the DEM and the elevation at the end of the run showed 910ft (I did not start/end in the same place). The correct ending elevation based on the DEM should have been 650ft, so the altimeter drifted up by 260ft during the run. Someone I ran with used a Fenix 6X and their ending elevation was right near 650ft. Update: I added in the comparison graph in the comments section. Its weird to me that older watches would provide better data than newer watches. It seems that maybe the Fenix series are not affected by temperature change and/or they automatically re-calibrate the elevation during the activity (as suggested by the Garmin page here). 

"Before starting the timer, the elevation data field on the watch will preview the calibrated elevation.

Throughout the activity, the watch uses DEM mapping data, and GPS elevation to make adjustments to altitude for any altimeter drift due to pressure changes caused by a weather event during an activity."

Another Example

A recent test by DC Rainmaker (from here, picture below) also showed several watches having extremely similar elevation data and start/end elevation after a 12 hour hike (including the Forerunner 965). This was a long activity and several brands (including Garmin) seemed to have pretty good elevation data, where I still seem to have some issues even on shorter runs.

It would be nice to be able to trust the elevation data a little more given that this is the top Forerunner model. It seems like there could just be a setting to enable auto-calibrate during activities if there are major changes in certain environmental factors (especially temperature). Maybe it would just be copying how the Fenix 6/7's work, since they seem to be more accurate.

 

Does anyone else have similar issues with elevation?

  • I get my watch replaced due to this. Now it is super precise, but question is for how long time...

  • My Fenix 7 has done this for the last two years I've had it, but a bit more dramatically than the other examples posted. 

    7mile run with 950-1000ft elevations comes in at 14-1600ft, and I have to rely on "recalculate elevation data" on strava to get a sense of what's true. This happens consistently and i have two years of group runs that show it.

    I am a very heavy sweater, and run warm at all temperatures.

    In the winter if I have sleeves, I will wear the watch on the outside of my sleeve, and the same elevation-creep happens, presumably taking my body temp and sweat rate out of the equation.

    I think since altimeter and barometer readings are really just inputs to guess the elevation, the solution Garmin needs to implement is periodic mid-activity GPS based recalibration (with a phone connection if needed) or automatic recalculation once the activity is saved.

    Thoughts?