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Altimeter and elevation issues still occurring (calibration & temperature)

a77
5 months ago

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?

  • 0 5 months ago

    I am having exactly the same issues with my 955. I first noticed that the start / end elevation were always different (even though I start/ end always in the same spot).

    My wife has the 255music and the elevation plots look way better (we run together most of the times). I even did a run wearing both watches and the the 955 always drifts.

    I believe it's a software problem when using the smart selection (barometer and altimeter). What I noticed is that in reasonably flat runs, the 955 assumes most environmental changes (temperature and pressure) as elevation changes... Maybe the other watches have a different function to determine this?

    I'm already in contact with Garmin but after 3 email's I still haven't been able to explain this to the contact centre here in Iberia.

    I'll let you know how the situation develops.

    Btw, I have a post similar to yours on the forum (beta software for 955)

  • 0 5 months ago in reply to 9819108

    Same for me. Since firmware 17.xx in Beta I get way to many height changes counted by the watch. This is a screenshot for the last four hours, while the watch sitting on my office desk. 

    Sensor cleaning didn’t change anything, but I guess it’s a sw problem. 

  • 0 5 months ago

    For me this is an old Garmin issue. In my case the body temperature increases during the activity what makes the watch gives a lower altitude ate the end of the activity even if it's the same place as start. 

    It affects other measures cos the watch will consider I was running "downhill". But in the FR955 the difference is small. It was much bigger in my onld Vivoactive 3. 

    The Fenix7 has the sensors better positioned to the side of the case. Maybe that's why they are more accurate.

  • 0 5 months ago

    It mostly seems that is it too sensitive to temperature changes. I went for a short walk yesterday around some neighborhoods (not recording an activity) and the altimeter reading drifted up 35ft by the end of the walk (ending at the same starting location). It was cold outside, so the temperature reading on the watch dropped in the beginning of the walk. This pretty much is the same as most of my recent runs. The temperature graph shows a sharp decline in the beginning of the run and it causes the elevation to drift upward. Winter is starting so it makes sense that this is happening more if the temperature is a major factor. I haven't looked back at my summer runs but I would imagine that the elevation drifts downward if the watch temperature increases during the activity. I guess if the temperature fluctuates both up and down during an activity that it will overestimate both the total ascent and total descent. This is pretty stupid because its an outdoor watch and its so affected by temperature.

    Its just annoying because the Fenix series doesnt seem to have the same issue and therefore there is probably some sort of software difference. If anything, I would have expected the Fenix to have worse issues because the sensor is more exposed on the side of the watch.

  • 0 5 months ago

    This is the comparison to the Fenix 6X that I had discussed in my initial post. My F955 Solar is in red (drifting higher) compared to the Fenix 6X in blue.

    Im not sure how much I trust Strava elevation corrections, but I added them in for a comparison. The colors changed for the below image. Forerunner (red), Fenix (green), Strava Corrected Elevation (blue). The Fenix looks way closer to Strava:

  • 0 5 months ago in reply to a77

    Here I have screenshots of 3 runs on exactly the same loop. First image is the real profile from a run in July, the other two are with the latest firmware. Temperature was no issue last winter. 

  • 0 5 months ago

    FWIW i have the same issue with my 255M.  Runs usually end up at a higher elevation than the start.

    If its a hilly course its not as obvious but somewhere flat its very clear.

    My guess is the pressure sensor isnt temperature compensated as as the watch temperature changes during a run it logs this as a change in elevation.

  • 0 5 months ago

    I had exact same issues from may to november. I did this topic about it. Long time i thought it have to be somekind of software bug and it will be fixed soon but no. New software versions came but altimeter problems weren't fixed. In the beginning of november when software 17.xx was released to public beta i did this bug report too. Eventually garmin agreed to repleace my watch under warranty. Now i have new watch since mid november and everything seems to be working fine again. Absolutely no problems at all with elevation or barometric data. So I advise you to contact garmin support. There isn't much help you can get from this forum except maybe confirmation that these altimeter problems exist on some FR955 watches. Dont know why.

  • 0 4 months ago

    I’ve got the 955 forerunner solar and suddenly I’m doing a 40 minute run and it’s recording 56,000m elevation on a 20 metre course !! Consequentlyy TSS is in the thousands !!

    we’ve just gone skiing and same again but also I’ve covered circa 40-50km but it says I’ve ski’d 1902km today and again elevation is ridiculous 

    any suggestions to correct , greatly welcome , I’ve cleared the sensor hole but no change!! 

    I just wonder if it’s a data/ system issue and you have to go and find the first activity it did this and then delete everything since as this was a resolution on 920xt issue a few years back!!