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Altimeter and its calibration

Former Member
Former Member

Hi guys

I just got my FR945 and am having a bit of trouble with the altimeter. (I dont know if that matters but pls note that my watch is NOT connect to any smartphone)

First thing is that i would like to understand the meaning of the "Calibrate" and "Auto Cal." fields (a bit disappointed that the instruction doesnt say much about it)

In "Calibrate", I see "Enter current elevation?" with possible answers "Yes", "Use DEM", "Use GPS". From what I read GPS is not a good idea, is that true?

If I know my current altitude (for example my home) is it better to directly input the altitute as a number or to do a "use DEM"?

What's the effect of such a thing anyways? Is it just one shot? Is it good practice to do it every day? Every week?

In "Auto Cal." I find "During Activity" (Continuous/At Start/Off)and "Not During Activity" (On/Off). I have default values of "Continuous" and "on" respectively. What on earth is the effect of these options?? Am I right in saying that they are not discussed in the user manual?

In any case, when I first used the watch, the altimeter was showing a roughtly correct number of 520 in my home (I m not sure of my altitude exactly but i m quite confident it s between 510 and 530). After a few days it started reading, in the very same home, 480. Ie it lost 40 meters. Is that considered acceptable (I hope not)? What it maybe b/c the weather changed?

Thanks a lot

  • Use GPS = estimate elevation using the GPS fix, generally the worst option due to the way it is calculated.

    Use DEM = get position using GPS, then look up the corresponding elevation at that location from a database.

    "During Activity" (Continuous/At Start/Off)

    This does a calibration of the barometer using the computed elevation either once as you start the activity, or periodically during it.

    "Not During Activity" (On/Off)

    This does a calibration of the barometer using the computed elevation once a day.