New Altimeter algorithm not working, firmware is 20.30

Same here. In Sweden, home altitude is 55 and I just manually calibrated it from 65 to 55. Not sure how bad since 19.20 since I don’t usually check altitude at home when not in activity.

I've been using all beta versions since 19.20 but never paid much attention to altimeter drifts. There has always been a drift and as you say the weather currently change from sun with no winds to cloudy and windy the day after which makes it very difficult to compare with how it behaved two months ago.

My settings are Autocalibration: Off (which now is the same as nightly) and Sensor mode set to Auto.

I will try to look at it more closely.

My ground floor is about 43m above sea level and most of my time during the day and night is spent on second floor. Living on the west coast of Sweden.

Did you had any of the betas installed, or did you go the "normal" route with new firmwares via the phone ?

I have had betas (one) on my phone, but backed out and re-installed 19.20, and went on from there.

Yes, drifting has always been there, but not to this extent. I rarely had to re-calibrate, and when I did had to do it, it was usually from +/- 1 meter.

Went from 19.20 to the beta 20.01, then the betas after that until 20.30 (manually installed).

Re calibrated when I posted the first message, and now it's like this. If everything is working, the altimeter plot should be completely level around 55 meters. I wonder if some of the betas did something with the settings.

I have set my altitude to 55 meters now, and set the calibration mode to auto calibrate every night. Will see if it makes a huge difference regarding the drift.

For me it rarely drifts more than 10m, I have all calibration on auto. It was at 440m this morning then jumped to 453m (this is the actual ground level at my location, but I am at the second floor) around 11am and it stayed that way until now. No drops, no variation. I'm really curious what messes it up for you....

Oh and I went from 19.20 to 19.70 to 19.20 to 20.01 -> 20.04 -> 20.30 btw.

I set it to calibrate only during the night, approx. two hours ago. With that setting, the altimeter should be stable, right? This is how that turned out.

Thinking of going back to 19.20 now, and stay there until it's a confirmed fix by Garmin, for everyone.

Calibrate during the night just means it will correct the value during the night if necessary - not that the value won't change. Any air pressure changes can make it fluctuate. Maybe it's happening more if you're closer to sea level.

The altimeter was misbehaving way more when I left it at "nightly", so I went back to "auto".

My watch also behaves very well. One thing that I have learned coming from Garmin Instinct is that I have to be very careful with the sensor holes. Drops in pressure very often come when the sensor holes are clogged and most of the time what clogged them is water. During the pandemic we tend to wash our hands a lot, we have to remember to dry the watch and clean the holes. After washing my hands I remove the watch, shake it and blow in the holes to remove the water.