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Barometer/Altitude issues

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  • Plummeting elevation drops

    Originally posted by PIERRE.DELALY@GMAIL.COM View Post
    For those of you interested, Garmin was very responsive and did not make a problem at all to take it back; good surprise. I am getting the FR210 instead, am forgetting about barometric altimeter.
    I have no confidence in the barometric altimeter. One might expect to see an "out and back" with elevation to be symmetrical on a graph...but my runs are barely recognizable on screen. The GPS function is much closer to reality. :/ Yesterday, in Bike Mode on the stationary trainer, I watched my elevation drop 200ft! I can live without elevation data but the heart rate function is also jacked up. double :/


    • I've done three treamill runs this week and have had some really bizzare altitude issues

      run 1 elevation gain 197ft
      run 2 elevation gain 180ft
      run 3 elevation gain 207ft

      this is all on the same treadmill, constant temperature, same time of day, the weather was the same (pressure variations a few millibars).

      Has any experienced this?


      • what did the graph look like? Was it pretty flat? In the latest firmware, they greatly improved the altitude graph but seem to have taken out any filtering for ascent calculation, leaving that calculation pretty much useless. Two other factors that could impact an initial change in elevation are it warmed up on wrist or the temp where you have the treadmill was different than where the watch had been being stored just before the run.

        If you consistently see this, it'd be interesting to see if you ran with your watch sitting next to you rather than on your wrist. This would remove both any temp diff it is getting from your wrist as well as remove the potential issues where by being on your wrist, the pressure holes on the back are being plugged.

        Also, many software programs re-calculate the ascent from the raw altitude data rather than relying on the number computed from the watch. They will usually take out the noise of small ups and downs of a few feet. Note that this is different than the "corrected" altitude in Garmin Connect which throws all the altitude data out the window and calculates the elevations from known survey maps and the recorded GPS coordinates.


        • Hi Ekutter,
          Here's the links to the files, ignore my performance lol coming back from achillies & rotator cuff surgery (some numpty knoced me off my bike) so I'm not fast :-(


          Weights workout - the garmin was on the floor for the workout under the bench in my bumbag!

          I normally wear the watch on my wrist but the face placed so that withmy thumb up I can see the face, this leaves the wholes on the watch open to the air. I like to be able to glance down and see the face without rotating my wrist.

          I'll give it a go with the watch placed on the treadmill when I do a recovery or base run.



          • The actual elevation graphs look pretty good except for the more extreme single blip downward on the 2nd. This is about as good as we can expect. The elevation gain issues are caused by what seems to be Garmin disabling any filtering on the data. They shouldn't count bumps of a couple feet. Polar used to use a value of 20'. Less than that and it was considered noise from subtle changes in air pressure. With that filter in place, 2 of the workout's would have been zero ascent, and the other 2 40' to 60'. Still not 100% accurate but within acceptable ranges.

            I also wouldn't worry about the different ranges between the workouts. If you want that to be consistent and more precise, create a way point and set the known elevation. If you are within 50' (I think) of that location when you press the start button, it will calibrate to that elevation. The differences you see are well within what you'd expect with this hardware and variables with barometric pressure.

            Bottom line, ignore the ascent value reported by the watch. It tends to be accurate on long climbs and descents, but not for other workouts. It was working better before the last firmware upgrade so should be a relatively easy fix for Garmin.


            • Thanks for the advice about using waypoints I've set a couple up one at home, work gym and the gym near home so I'll see how I get on.


              • There have been many reports of elevation problems with the Garmin 910XT, and pleadings for a software fix to address.

                Unfortunately, this cannot be resolved with a software update. You must send your watch in to Garmin for servicing.

                A random number of 910XTs have faulty barometers in them. There doesn’t appear to be a pattern of serial numbers affected.

                To determine if your barometer is faulty. go in to the diagnostics mode:

                1. Power off the 910XT

                2. While first pressing and holding down the Enter button, press and hold the Power button.

                3. Continue to hold both the Enter key and Power button until the diagnostic screen appears.

                4. Release both buttons.

                Now that you are in the diagnostic screen, press the Mode button, exactly 7 times. The 910XT should beep each time the Mode button is pressed.

                If the third line called “Baro Alt” shows 65,000 ft or 20.00 m and the fourth line under “Baro Pressure” shows 0, then your unit is faulty.

                Power off the 910XT to exit out of diagnostics mode.

                Call Garmin at 1-800-800-1020 with this information provided and they will send you a new watch.

                If you are out of the warranty period, as I was, they will send you a factory refurbished unit, even if the warranty period has expired.

                If you want to keep you existing unit until the new one arrives, Garmin will charge you $199 on your credit card as a deposit and when refund you when they received the old unit back.

                If you stumble on a support rep who will not help you, simply call back until you get one who is more sympathetic and customer focused.