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Altimeter accuracy issue

Trunning
over 2 years ago

After using my Garmin 255 device for 1 month and a half, I noticed that it has a problem with the barometric altimeter.

I don't know if it's a software bug or a design flaw.

The problem is the following:

-Every time I go for a walk or run in the mountains and make large height differences, I calibrate my device just before starting at a known height point.
-At the end of the activity, the positive accumulated slope and the negative accumulated slope is the same.
-However, during activity, the watch shows a lower height than the original. This difference increases as I climb higher.

For example:
-Start: 1000m real altitude: Garmin shows 1000m (just calibrated)
-If I climb to a real altitude of 2000m: Garmin shows 1800m.
-If I keep going up to 3000m real altitude: Garmin shows 2500.
-The most disconcerting thing is that when I return to the starting point it indicates the correct height again: 1000m

Normally these errors appear from slopes greater than 100m.

Has anyone else had a similar problem? is my unit defective?

Thank you very much for your relaps.

  • 0 over 2 years ago

    I can understand you 100%. 
    I wanted to use a Garmin watch twice. 
    Always the same experience. 
    It is not accurate for bigger ascents.
    I don‘t get it whats so hard about that.

    Thats why I use SUUNTO 9. 

    Also tried DEM which made it even worse because of map accuracy in peak areas. 

    Unfortunately I have to say that SUUNTO is the better mountaineering tool. Garmin has a wider health spectrum with very good HR on wrist. I really do not know, why Garmin does not put more effort in making it more accurate refering ascent and altitude.  

  • 0 over 2 years ago in reply to 2780939

    The truth is that if I put the device in only barometer mode, it has extremely precise readings, so the sensor is really top quality. All readings are identical to my iphone's barometer no matter what height it is.


    The problem I think is the height calculation algorithm.

    Let's see if we are lucky and garmin corrects it in a firmware update.

    It is very annoying to see how watches from other brands that cost half the price are much more precise in this regard.

  • 0 over 2 years ago in reply to Trunning

    It's a very hard bug from maybe all Garmin watches. The conversion from barometer to altimeter maybe related to temperature of 15°C at sea level. If temperature is high (as now in Italy to 33 °C at sea level) the altitude from barometer is understimate from 5 to 8 %. The SUUNTO watch combine data from barometer and GPS every second in order to keep tracked the barometr to the right altitude. WHI Garmin doesn't do the same? I really don't know.