Elevation and altitude wrong

Many other owners of the FR955 have the same issue, me too...you can find many topics with this problem. Its a problem between the barometric and temperature senzor, when the temperature goes down, altitude gain rises or falls but sometimes drastically. It looks that booth watch have the same senzors, mainboard (same fw) etc, only display is different. I have returned my 955 for constant problems with barometric height

I had the same. Was telling me I’d gained 500 ft overnight. Was getting 12 x flights climbed during a day at work. 
I emailed support and they sent me a replacement watch. I still get odd fluctuations but it’s far more stable (and seems reliable when running which is the important bit. Was getting massive elevation gain on flat courses). 

I have similar issues with my ForeRunner 965. I am using two different widgets from the IQ connect store for gps position measurement. The position measurement itself works very accurate. Both widgets are able to display the altitude as well. But even after manual calibration of the altitude or barometric sensor of my FR965 both widgets show the same wrong altitude which is about 40 meters higher than the actual altitude. It is strange.

Thanks all for yout feedback even if this is not reassuring.

Do this issue appear also recently for you and did your forerunner work good at the beggining ? 

Personnaly, using the 965 since June 2023, I was very satisfied about it until February, with no big issue of elevation and something else. But now I am not confident about the values on the display...

Last walk : also  wrong elevation gain (around 65m instead of 35m). Looking to others stats and graphs, I saw some other issues that altitude is false due to the impact of temperature measured

• start : altitude 372m. Temperature sensor = 29°C
• end (same point) : altitude 408m. Temperature sensor = 23°C

Will see in parallel with Garmin support 

I noticed this problem 4 weeks ago, first. But thus was the first time I tested these widgets and was interested in altitude measurement. But I assume, this is a general problem with the FR which was inherent from the beginning.

My 965's barometer has sudden jumps and corresponding altitude drops (and the reverse) all the time. It stabilizes overnight 200ft too high despite manually setting baro & altitude beforehand and will jump all over the place. Every morning simply picking it up results in the altitude plummeting, and walking done a flight of stairs will drop me 300ft. It's been like this since day one. Out on a run it's all over the place, it'll climb a few hundred ft going flat, or drop me below sea level at the end when I go down a small hill to home where it's 300ft elevation. I'm not sure if this is my new unit or inherent in the device and not many people have checked or assume theirs is accurate.

Is your watch typically connected to your phone for syncing?  Activities sync right away and show up within a minute or two of saving (without opening app manually to sync)?  Do you have any battery save modes or data saver settings for the Garmin Connect app?

I have only had mine for a week now, but elevation of all my activities look pretty spot on even when running without phone. Much better that my 945 was, although it is much nicer now in MN that it isn't winter, so temperature calibration/adjustments  issues are not such a huge deal.  Elevation now at my office looks good as well.  I don't regularly look at the ABC widget or others that would show live elevation on my watch however.

Nope, it's 99% disconnected, hence why the alti & baro are pure sensor based and not potentially corrected for activities by GC/Strava. It's nothing to do with needing/having a data connection

I have only loosely looked into the auto/calibration of the sensor... but it is based on your phone and connection to GC I am pretty sure.  Similar to wind speed data and running power calcs.

Curious, why do you have it disconnected all of the time?   

Also how are you so sure that your phone/location/GC has zero impact on the elevation/sensor calibration?  Have you contacted Garmin on this? Work in programming or support at Garmin?

It's definitely not based on your phone, that's the whole point of them. I don't know if it can correct current values on sync, I doubt it considering how woefully inaccurate the weather data is using stations miles away. Why would I want it connected all the time? It's a watch, I don't need it syncing steps every hour and don't want phone notifications all the time. I sync after a few activities that's it, I mostly use my watch as a watch and tracker.

I can't see why I'm supposed to have GC connected to look up a barometer reading of my current location to track pressure and thus altitude, again that's the whole point of these watches. Most people seem to think their barometer/altimeter works fine, perhaps so, or they may not notice as it's corrected in GC, but my F6Pro was very accurate and didn't have of the issues my 965 has in this regard.

By GC correction I mean the Garmin web where it will look up the DEM of the route and use that while discarding the watch-recorded values for alti