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Inaccurate measuring (altitude on a track?)

Heye_S
over 4 years ago

Hello kind folks,

today i did a little track session with my sister. I'm on a Garmin 735XT and my sis is sportin' a Forerunner 945.

When we compared the recap on the watch, we stumbled upon a difference in the pace, although we did the whole session side by side.

I looked up the activity on strava and on her watch we did about 120m of altitude (on a flat outdoor track, no tree coverage, good GPS signal).

If you compare the tracks you can also see the massive difference:

Any way to fix this? The 945 ist running the latest firmware update...


Thanks in advance!

  • 0 over 4 years ago

    Hi, Use the Track Run -sport, it's has magical error calculations to the bad Sony GPS chipset.

  • 0 over 4 years ago
    Heye_S said:
    on her watch we did about 120m of altitude

    Her 945 has a barometer to track altitude. That works fine if the air pressure doesn't change. (and the air intake hole in the 945 isn't clogged up).

    Your 735 doesn't have a barometer, so it used gps for altitude. gps for altitude isn't that accurate and will detect changes in altitude more slowly than a barometer, but for most running and biking activities it's fine. 

    Your sis could set the barometer to only be used as barometer and not altitude. That would solve the problem that you run on a flat surface but stil gain hight. 

    I really don't see the point in using a barometer for altitude. Some watches have automatic hill detecting, so it reports hill repeats (Polar has this). But if you do hill repeats, you kinda know you do and did plan to do. Don't need confirmation from your watch. 

  • 0 over 4 years ago

    To give you a little update:

    Today we did a quick test and ran 5k together, she used the "Track Run - Sport" Mode.

    The 945 showed 3 meters of altitude, which is okay i guess, its a flat track, but 3 meters altitude on 5000m distance should't alter the measurement...

    The root of the problem persists, although we have now comparable measures of altitude her splits are 20s slower than mine.

  • 0 over 4 years ago in reply to Heye_S

    Prior to the 5k did you guys do an activity (as a warm up) to calibrate the track? With proper calibration this is what a track workout should look like.   versus without track mode   

    With the track mode turned on you should be able to get ideal tracking if it has been calibrated. The track mode is by far the most accurate way to record track activities. My guess based on that you have elevation is that the track wasn't calibrated correctly, as the track profile should be zero. Below this I've shown what a calibrated activity vs a non calibrated workout. 

     versus non calibrated