Two watches, same activity, wildly different Total Ascent outcomes...

Mike Montaño said:

Total Ascents are off: My watch lists "Total Ascent (ft)" as 1,914ft, hers as 3,014ft

Open both activities in Garmin Connect Web, and enable "Elevation Correction", then post how the elevation changes in both activities, and which of the devices is right or closer to the cartographic value. The other one might have dirt or moisture in the pressure sensor port.

Also have a look at the document Troubleshooting the fenix 6 Series Altimeter and Barometer | Garmin Customer Support

It seems that Elevation Correction is the culprit, but I'm not sure how hers was automatically enabled (which shouldn't happen with the type of watch she has) and my was automatically disabled (which is supposed to happen). We've both never accessed the desktop version of Garmin Connect until yesterday, so there's no way either of us could've manually set it. 

If I remember correctly elevation correction is automatically enabled for watches without a barometer 

Edit: just realized you both have the same watch, I have to read more carefully 

Mike Montaño said:

I'm not sure how hers was automatically enabled

Please share links to both activities. With a little bit of luck I can see in the background JSON data whether the pressure sensor on her watch was functional. Does a different elevation profile appear, when you turn off the elevation correction in her activity? Also let her check the altimeter on the watch. I am not familiar with the F6, but perhaps it is possible to disable the sensor in the settings.

Sharing a Garmin Connect Activity | Garmin Customer Support 

I have been running exactly the same route for training very often for months.
It is a long staircase with a precisely measured height difference.
The deviation from the measured value compared to the altimeter of the watch was -5% on average with my new watch. I still found that acceptable.
I am talking here about an average value that is made up of more than 1000 laps. The values are therefore very well comparable.
Interestingly, the deviation has increased over the months more and more and has now arrived after 10 months at +17%!
I have of course calibrated and cleaned the altimeter regularly.

A Garmin employee even told me on the phone that 17% is normal.
Really?

MaxR6 said:

A Garmin employee even told me on the phone that 17% is normal.
Really?

Well, besides others, it depends also on the weather. If the atmospheric pressure varies more during the last time (which would not be surprising in August, in many parts of the world), then the changes of the pressure during your runs may have indeed an important influence on the accuracy (when in an outdoor activity, the sensor is locked in the altimeter mode, hence barometric changes will result in a change of elevation).

But of course, there may be also other factors involved - dirt, sweat, or moisture accumulated in the pressure sensor port, or the influence of the temperature and rapid temperature changes (for example walking out of an airconditioned room before the tun), etc. Have a look also at the following document: Troubleshooting the Altimeter and Barometer | Garmin Customer Support 

Did you really read my post?

MaxR6 said:

Did you really read my post?

Yes, I see you wrote you cleaned the port, but did you read the rest of my post? BTW, the altimeter calibration won't have any impact on the reported elevation gain. It only influences the absolute value, not the gain. And it also does not eliminate the influence of the atmospheric changes during the activity.

... maybe the influence of the atmospheric pressure on the reported elevation gain will be more clear on an example:

Let's say you start your activity at the pressure of 1013 hP. You complete it an hour later with the true elevation gain of 30 m, however the atmospheric pressure drops by 3 hP to 1010 hP in that time (at an approaching storm it can drop by up to 30 hP!). The difference of the 3 hP results in the difference of 26 m - it means it introduces and error of almost 90% in this specific example. So from this point of view your 17% is quite perfect.

And that's only the atm. pressure aspect. Now add the influence of big temperature changes, sweat, wind gusts, ... and the deviation will grow even more.

trux said:

BTW, the altimeter calibration won't have any impact on the reported elevation gain.

trux said:

It only influences the absolute value, not the gain.

The change in air pressure and the altitude gain calculated from it very much depends on the exact altitude or on an altimeter that has been calibrated exactly. The air pressure and also the air density is different in different heights and accordingly also the calculation basis for barometric altitude formula.
For the formula to calculate the difference in altitude due to air pressure, the exact altitude is always mandatory.

At different altitudes, the air pressure also changes differently for the same altitude difference traveled.
Or in other words. to achieve the same air pressure difference I have to travel a further distance at a higher altitude.
Simple mathematics. Details under barometric altitude formula.

But that's just by the way, I didn't want to leave your erroneous statement here.

trux said:

And it also does not eliminate the influence of the atmospheric changes during the activity.

No one has claimed that

Back to the topic:

MaxR6 said:

The deviation from the measured value compared to the altimeter of the watch was -5% on average with my new watch. I still found that acceptable.
I am talking here about an average value that is made up of more than 1000 laps. The values are therefore very well comparable.
Interestingly, the deviation has increased over the months more and more and has now arrived after 10 months at +17%!

Again, I am aware of all the influences and reasons for measurement errors, but they do not play a role here, because we are talking about of average values. This is about the statistics.

Weather, dirt, wind, temperature, cover of the device. All these are external influences or random measurement errors.
In statistics, the inaccuracy due to such errors is reduced with the help of more frequent measurements.
Since I have run and measured exactly the same course over 1000 times, the measurement error is statistically small.
If this average now also chonologically steadily increases, then a change is statistically proven here, which cannot be based on any coincidental.

But anyway, it's clear to me that you trux can't help me here at this point. No problem.
Thanks for your effort.
I just wanted to express my disappointment about the quality of the product and the service of the support here in the forum.
Nothing more, really.