Barometric Altimeter is frustrating

Yep this behaviour seems to be quite common... Those sharp changes are probably calibration attempts against GPS readings. 2 things you may try:

1. When starting your activity, wait for GPS fix, then wait for 30 seconds and then press start. These 30 seconds give the watch the chance to calibrate its altimeter against the GPS readings before it is included in the profile.
2. Try GLONASS instead of GPS or visa versa. Maybe it provides more accurate calibration data.

I‘ve been experiencing this since January as well.  Don’t think it’s a GPS problem because:

• It happens despite waiting for more than 30 seconds each time
• The elevation starts out correct, then drops 200+ feet during activities on a relatively flat course

The altimeter adjusts based of temperature as well as pressure (so I’ve read elsewhere on this forum), and seems to be dropping as ones skin heats up.    I believe this is a software problem that was introduced in a firmware update about 6 months ago.  It would be nice if we could revert to an older firmware.  I wish Garmin would fix this.  

This would make sense as the temperature sensor on the watch seems to be for skin temperature rather than ambient temperature. 

For the above reading I had GPS and Galileo on and I made a point of waiting for a minute before I started the activity ...

I have heard about the actual sensor needing to be cleaned as it's in a pretty vulnerable position for collecting salt etc from sweat. Might look into trying to clean it ? Does anyone have experience of this ? Perhaps it's just flawed software but probably also a quite weak sensor. 

It's flawed.. I have tried everything, including cleaning the sensor. Nothing works..

I have noticed that if I walk or do a slow activity the elevation seems to look correct. The problem is if I do a faster run it gets way off. I suspect the algorithm doesn't know how to adjust for  one or more of the changes that happen when someone works harder. Eg, heat,  sweat, blood pressure. Whichever one effects the sensor.

Eperiencing the same issue here. I believe the pressure sensor / processing of the ambient pressure is off (the readings of pressure were of >10hPa). I got in touch with garmin product support but still waiting on a solution. I'd rather have the barometric senor turned off completely as it is rather annoying now, However I don't think it is possible.

Mine has been like this for over a year now, and is now a random number generator, even if shows same basic profile, starts higher than ends with much lower same starting elevation (up to 10,000 meters difference, which would be great if I were a commercial jetliner). Ports on back apparently clear. This is not a problem of waiting or using GLONASS. This appears to be a firmware issue IMO (which will NEVER get fixed apparently). I have same suspicion that it's body heat or sweat during activity causing the problem.

Same problem here. This started on july 1st. Before the values where much more realistic.
On rounds with 0 to 40 m I now get 150 to 550 m.
I also notice the difference between walking and running. While walking I get 20 m higher values than while running.

Resetting the VA3 to factory defaults dit not help.
I clean the VA3 after every activity under/in warm water and now also tried cleaning the altimeter port hole by soaking the watch in warm water with a little mild detergent.

My VA3 is throwing off huge numbers.  This was a relatively flat run and mine shows a 17.5K elevation gain.  

Polydactyl said:

I wish Garmin would fix this.

very funny joke!!!