Altitude calculation during run activity

Hi,

Yesterday I had a quick run using the small break we had from the weather conditions in UK. However, the sky was cloudy with thick clouds and pressure was changing (I think).

What happened was that the altimeter was giving the wrong altitude with negative values. I even calibrated when I saw the negatives values, but altitude drifted again.

Before, I report it to Garmin( if this happen again), I'd like to know how the watch measure the altitude during an activity. I searched on the forums and I'm not sure if this still applies to fenix 7 series with the new altimeter calibration. Does the watch use DEM and GPS to calculate altitude or once is calibrated the altitude is calculated based on pressure?

I had my settings as: auto calibration: On; Sensor mode: Auto.

Thanks

Top Replies

All Replies

0 Snowbren over 3 years ago

I get negative values being at home on Epix…to the tune several hundred feet below sea sea level when I know my usual altitude. Not sure why this happens occasionally.

0 Clatecnofilo over 3 years ago in reply to Snowbren

At home, it uses the barometric pressure to calculate the altitude and depend on your settings it can drift. For example, when pressure changes are quick, if you've got your sensor mode in auto the altitude will drift, even when it shouldn't because you're sitting in the sofa. When there is this really bad weather I change the sensor mode to barometer only. So, altitude stay as calibrated.

0 4241327 over 3 years ago

I guess they mucked up altimeter calibration on all watches. Of course, the new watches can't roll back to an old software version.

It's a disgrace, because the old calibration worked fine and also took movement vs resting into account. I especially don't understand why users are required to send in screen shots to tech support. The forums are full of them.

Garmin's quality assurance has always been subpar, but now it's a shambles. Just look at the Venu 2 forum or the problems with the new Instinct 2.

0 Marc_v_L over 3 years ago

Somehow the Garmin watches (experienced it with fenix 5/5X, Forerunner 935, Instinct) have a hard time to see the difference between a rapid weather/pressure change and actual climbing/descending. I usually leave it on Auto, but after a few days or even hours, it can already be off by a few millibars. So right now, when at home, I put it at barometer mode.

I think that during an activity it’ll calibrate at the start and then change according to the pressure changes whether that is weather or climbing.

0 Snowbren over 3 years ago in reply to Marc_v_L

Hi, I followed a tip I saw on the5krunner.com, which is to use a website to confirm your elevation and then manually enter that value into the Altimeter settings. Will see if improves the consistency as I move. There was a 50 foot or so difference between website and current value the watch was showing on home screen.

0 Clatecnofilo over 3 years ago in reply to Marc_v_L

That is what I've read in old posts in Garmin Forum that It's using the barometer to calculate the altitude. In my opinion, when the watch shows negative values, it should check with the GPS and DEM to auto calibrate and I had the impression that it was the case with auto calibration on

0 Clatecnofilo over 3 years ago in reply to Snowbren

Sorry, what do you mean? You can calibrate the watch before start the activity using DEM, why do you need to check in a website?

0 drkglb over 3 years ago

My Fenix 6 already struggled to get good altimeter data in certain conditions (wind mostly) and unfortunately it is the same with my F7.
On today's run - which was mostly flat, maybe 10 m positive and negative ascent to reach the 400m training track, I got this altitude curve :
https://ibb.co/QQvyV5f

Result : 77m ascent = Completely wrong. Strava DEM correction gives a much more realistic value of 9 meters total ascent.

I think this is because of the fast wind messing up with the barometer.