The barometric altimeter

Hi, I've also had the same issue with barometric GPS, it massively underplays my true elevation gain. Is there any way to deactivate the barometer, or just get the watch to use GPS elevation as standard instead of the barometric?

If you're paying attention to elevation as you run, there are separate data fields for (Barometer) Elevation and GPS Elevation. Within Garmin Connect, you can enable Elevation Corrections on a per activity basis, so you might try it to see how much of an effect it has, though you can't change the default for your device AFAIK.

You should also give your watch a bath in soapy luke warm water to make sure the ports that let air in to the barometer, just counter clockwise from the Start/Stop button, are clear.

Elevation correction in Connect and Strava is essential to get sensible results which really defeats the entire object of having the barometer. Many people have asked if Connect could have the option to always correct elevation.

Hello,

I have a Forerunner 645 since 5 months. I had this altimeter issue and Garmin support replaced my watch by an other 645. There is still the same issue.
Since the covid-19 quarantine I do every time the same running route, therefore I know exactly the altitude value of every peak point and the number of elevation meter of every climb.
During one of my last activity I detected when the watch stopped measuring correctly elevation (I put on the watch face the total ascent and the altimeter elevation).
During a climb which lead me to an altitude = 64m, I saw, when I arrived at the peak, that the altitude given by the watch was = 52m instead of 64m. Therefore I stopped running, I stopped moving, and I saw that the elevation was updating meter by meter very slowly (every almost 30 seconds). The elevation increased gradually : 53, 54, 55, etc, until 62m after 2-3 minutes whereas I didn't move. It was like if barometric altimeter had correctly measured the altitude evolution and transferred data to the watch but the watch was blocked in a state that prevent it to update elevation data in real time.
Then, I stopped the activity, waited for 20 seconds and resumed the activity. After that, the Forerunner 645 updated elevation data in real time (it was not blocked anymore).

It seems there is a software bug which prevent the watch to update in real time the elevation data given by barometric altimeter. Is it possible to correct it in a future update ?

Thank you.

I have had this same issue as well and indeed, just press stop/start and it clear the issue.
It may be possible to fix it, but you need contact support and ask log a bug for development.

I've just bought the 645(music) to replace a POlar M400. my main activities are orienteering, trail running & cycling. SO glad to hear that it's great for orienteering! I too am having issues with the altimeter - yesterday I did a routine 5km  - out & back 2.5 km each way. The first 1km has a slight downhil gradient, but garmin has me climbing by 140m! This 1km is followed by a sharp incline, where Garmin has me running downhill! I already dislike the limited athletic opps available on the watch as Polar has over 200 activities available and this is furthering questioning this choice of watch.. 

Hello,

For your first 1km, it is possible that you didn’t wait enough time after getting GPS sync to start your activity. At start, the 645 calibrates altimeter with GPS. If you have a good GPS signal, this calibration is instantaneous, but if the signal is low it can take several seconds. Therefore if you start activity and 10s later the altimeter is calibrated 140m higher than previous value, you will get 140 D+.

Add elevation data on the activity watch face to check this calibration.

for the second 1km, you may have been faced to the software issue of this watch. When you are in place with low gps coverage the software application doesn’t update anymore the elevation data in real time. You have to wait several seconds at the top of the climb and all elevation data will be updated.