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Altimeter issue

Leew72
over 6 years ago
Anyone else getting false elevation reading on the 645M ?? Mine is consistently overestimating by 600ft.. any way of calibrating this???
  • 0 over 5 years ago
    This morning before starting my running activity the altimeter was reporting -15m (I waited on a GPS fix). This should be 22-23m, which was also the value I calibrated via GPS the last time (see my previous post in this topic). So, why did the watch say -15m? When I manually calibrated the watch again using the GPS value, it determined a value of 33m. So, I decided not to accept this and entered the calibrated value of 23m manually. I am glad Garmin added the manual calibration option, but to me the way it is working makes no sense. If a value on a certain GPS location was calibrated before, why not re-use that value the next time on that exact location?
  • 0 over 5 years ago
    Have you uploaded the same image twice?


    No, both devices are reporting the elevation profile correctly after the FR645 v3.70 firmware release. Do note that each device started at different starting elevation values.
  • 0 over 5 years ago
    Just catching up with this thread. I am a 935 owner and wanted to swap to 645 but was put off because of the altimeter issues and lack of manual calibration option. Has this now been addressed in a firmware update? Is the altimeter now as accurate as the 935 / Fenix? Can you tell me if there is a way to view current altitude without starting an activity, such as using the ABC widget?
  • 0 over 5 years ago
    There is the myABC widget, and election can be shown on a number of watch faces.

    3.70 allows manual calibration of the altimeter.
  • 0 over 5 years ago
    No big issues with altimeter so far. One think I found, the watch history data screen does not always show correctly the highest point (top) of the route. Garmin Connect shows it correctly. Looks a software bug.
  • 0 over 5 years ago
    Updated to 3.70. First hike and the altimeter is off by 900m !!! and it never corrected itself even though the GPS reception was good and GPS tracking during activity was also on. Later calibrated the altimeter and it was showing correct value, few days later it is off by ~100m now.
    I seriously doubt now that Forerunner 645 has barometric altimeter, very unsatisfied with garmin now.
  • 0 over 5 years ago

    The 645 has no barometer/altimeter. It bases it's altimeter data on GPS location.
  • 0 over 5 years ago
    The 645 has no barometer/altimeter. It bases it's altimeter data on GPS location.


    do I misunderstand the chart or false advertisement on https://buy.garmin.com/en-US/US/p/612476#specs

    ciq.forums.garmin.com/.../1396003.png
  • Former Member
    0 Former Member over 5 years ago
    ImDisaster The 645/645M most definitely has a barometric altimeter. I'm not sure where you received that information, but it's incorrect. It uses GPS for elevation and the barometric altimeter adjust the altitude based on elevation gain/loss or changes in pressure.
  • 0 over 5 years ago
    ImDisaster The 645/645M most definitely has a barometric altimeter. I'm not sure where you received that information, but it's incorrect. It uses GPS for elevation and the barometric altimeter adjust the altitude based on elevation gain/loss or changes in pressure.


    I'd be interested to know if the barometric altimeter sensor is the same physical unit as the one inside the Fenix 5 and 935. There must be a reason why Garmin decided to remove the Altimeter widget on the 645 - perhaps due to inferior hardware?