Elevation on latest FWs

It does look ok, and from your posts in the Fenix 6 forum you may not have the issue. Sadly several of us definitely do have the issue - and it is real.

This run starts by calibrating the altitude correctly, then despite doing a loop from my house I apparently ~130m below sea-level.

Here is another run on exactly the same circuit

Completely meaningless altitude plot, complete rubbish meters gained and lost.

You are lucky that your watch isn't affected.  Happy for you.  But, sadly, some of us are not having your experience.

And that is what makes it hard for GARMIN to resolve. It’s clearly not as simple as a hardware problem unless it is batch related. Neither can it wholly be software unless there is something extra that has been installed causing the issue; I have no add-ons. Or it could be a setting.

As you note I don’t see this problem on the Marq Athlete or the F6 Sol Pro that I have yet others have had watches replaced and still see the problem. Sadly I have no answer. But that does not mean that I do not believe the problem doesn’t exist. I don't doubt that it does.

Reference your post of 11 days ago.

I have been looking closer at the posts here and the F6 forum. What you have here is similar to most of the posts in the F6 forum. The elevation appears to be tracked well for the first 20 minutes or so before going wildly awry. Interestingly, someone noticed their temperature was fluctuating more than would probably be expected. I overlaid the temperature (from the watch) on my elevation plots and saw much less variation. Might be worthwhile overlaying the temperature on this trace to see.

This from last evening is typical:

There might be some correlation there, hard to tell.  Here is a half marathon activity from two weeks ago.  The elevation plot issues are clearly visible, the temperature does move around maybe more than might be expected but it isn't dramatic.

https://connect.garmin.com/modern/activity/5659701596

My 5k from the other night doesn't show any movement in the temperature once it settled after the first couple of minutes.  The watch still recorded a significant loss in elevation despite me running in a loop circuit, but temperature looked normal.

connect.garmin.com/.../5702119071

The weird thing is some runs are absolutely fine - admittedly less now.  It appeared for me in May and I've logged two different support cases with Garmin and I keep being asked to wait.  They last advice was to clean the watch - about as helpful as a chocolate tea-pot.

It feels like it might be a hardware issue to me, given that some users are completely unaffected.  Hard to see how this could be firmware given that we are all having degrees of the same problem.  One would expect the same problem with some pattern; I just don't see any patterns; hence my guess it is a sensor problem.

Interestingly on the second run the temperature flatlined while it was moving around on the first link you posted. Given also that the watch is affected by body temperature I'd suggest that 17.5C is probably quite low for that second run - assuming you were wearing it on your wrist against your skin.

There is definitely similarity between what you are seeing, particularly with the plot looking fine for the first 20-30 mins or so before spiking. Since the barometer requires temperature for calibration it stands to reason that a defective temperature sensor might be contributing to the problem.

IceBear said:

They last advice was to clean the watch - about as helpful as a chocolate tea-pot.

There does appear to be some basis for that suggestion as it is possible that the ports can get blocked. I did some muddy mountain biking the other week. The elevation plot was a bit sketchy the next time I went out. I noticed there was some mud so made a better attempt at cleaning the watch and all was good again.

There was a suggestion that the issue might be country dependent but since you are in Auckland and I'm in Hawke's Bay that idea might be put to bed.

Doesn’t appear to be specific to a particular sport, or country.  Many of my runs have a Tempe sensor being used on one of my pairs of shoes.  They have the problem as well.  Don’t know if the barometer uses only the watch temperature or not.  Either way something clearly not working.  I wash my watch often and usually shower a couple of times a day due to two workouts a day - my watch isn’t dirty

I have a hard time believing it’s hardware related b/c numerous people started reporting the problem right around the same time. Would be a strange coincidence. 

IceBear said:

They have the problem as well.  Don’t know if the barometer uses only the watch temperature or not.

The barometer uses the watch temperature for altimeter correction.

Upgraded to 12.20.  Same problem exist - elevation is complete rubbish.

They should call this a MARQ Stay at Home.  Clearly using them outside is asking too much.