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  • Another example of how superior the old Polar S710 baro function is compared to the GF910 baro function. This is from a five lap run today. One image is useful, one is... sketchy. You guess!
    Comparison S710/GF910.
    Garmin needs to fix this. There is no reason why the 910 should be any worse than the 10 year old Polar. Well, other than that the baro in the 910 is second assortment crap.

    EDIT:
    This is the actual (raw, unmodified) track that the GF910 created. As you can see it isn't very exact in many areas, meaning that the 910 will think it is somewhere else (uphill/downhill) than where it actually is. Is it this that causes the baro function to produce poor graphs? Is the GPS altitude taken too much into account? Should it be taken into account at all? After all, the S710 baro copes rather well "on its own".

    The raw GPS track from GF910.
    Last edited by ALAALA; 05-01-2012, 02:12 PM.
    DISTANCE: 3000M___ - 5000M___ - 10000M__ - 21098M_ - 42195M_ --- Current VDOT: ?
    PB______: 10:50,09 - 18:40,20 - 38:39,00 - 1:25:39 - 3:10:26

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    • My barometer just gotten worse. I have negative elevations throughout the whole bike course. As shown from this link. I'm not sure why, but one question though.

      If I key in a landmark with a known elevation height, but never pass by there, will the watch be smart enough to understand the difference between the points and come out with a reasonable elevation at my location?

      http://connect.garmin.com/activity/172089701

      Is it reasonable that elevation will be negative?
      A Bit of Swim, Bike and Run Blog - www.imdz.org

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      • Sorry if I'm a bit uninformed on the discussion - didn't have time to read the whole thread. My barometer also is very poor - much worse than my Polar was. On most runs it (flat, out and back) it starts off at an altitude and then slowly falls throughout the run, ending on a completely different altitude.

        Has Garmin said anything about this? Part of the reason I upgraded from the 310 was to get accurate elevation data - I guess Garmin doesn't know how to make a reliable barometer...

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        • Originally posted by JEVER98 View Post
          Sorry if I'm a bit uninformed on the discussion - didn't have time to read the whole thread. My barometer also is very poor - much worse than my Polar was. On most runs it (flat, out and back) it starts off at an altitude and then slowly falls throughout the run, ending on a completely different altitude.

          Has Garmin said anything about this? Part of the reason I upgraded from the 310 was to get accurate elevation data - I guess Garmin doesn't know how to make a reliable barometer...
          Something about this 910. My Garmin Edge 500 with the barometer works great.

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          • For what it's worth I had 2 pointers from Garmin; (a) it's worth calibrating your start point with a known altitude, and (b) the barometric sensor can go off if you are in stormy weather, or the weather changes during the activity.

            Not a magic solution by any means (far from it as you can't exactly influence the weather!), but my bad readings were indeed during an increasingly stormy session...

            That said, even in good/stable weather the altitude data is different to Elevation Corrected data. I assume Elevation Correction is more accurate, thus I have to wonder why I bothered to buy an expensive watch with a less accurate altimeter?!

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            • Originally posted by NEVILJAP View Post
              I was out for 40 minutes, and to me the conditions seemed pretty constant.

              Maybe I'll have to verify with a trustable barometer to see if the conditions really changed...
              Originally posted by KAFOLSKE View Post
              If the temperature increases or decreases and/or a low or high pressure system moves in while you are doing your workout, you will see an elevation change.

              I wouldn't call this good or bad accuracy, it is just a side effect of using pressure to determine altitude.

              Even if the watch compensated for temperature changes, it can't tell if the change in temperature and accompanying pressure change is due to a weather system or a true change in elevation.
              ... that's where GPS would be handy ... to aid in determine if weather or altitude changed

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              • Originally posted by LEFTY01 View Post
                ... that's where GPS would be handy ... to aid in determine if weather or altitude changed
                That's where I always hoped the combination of the GPS and BP would make more accurate devices for elevation. Unfortunately, Gamin hasn't figured out how to really take advantage of this. I'm sure it is a harder problem than it would appear. But I have not found my Edge with BP to be any more accurate over a longer ride than my 10 year old Polar that just had BP with no GPS. And the FR910 doesn't come close to that of the Edge.

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                • Hello all,

                  Just bought an 910XT, specially for its barometric altimeter, and finds it completely inacurate, like others did in the past. So I was wondering if there is anything new on that topic.

                  I was in the mountains yesterday and found three issues:

                  1) altimeter is very inacurate, moving (down) by 200 meters after climbing 1000 meters; weather has been and continues to be extremely stable.

                  2) computation of vertical elevation is completely off, I would say a smoothing / SW error ( when importing data on SportTracks, vertical elevation is much more reasonable than the one shown on the watch and on GarminConnect).

                  3) Calibration of altimeter: sometimes it works, sometimes not (getting back to a recorded point, altitude is not re-adjusted).

                  I have already upgraded my watch to firmware 2.50

                  All in all, very disappointed. I have contacted Garmin, am thinking of asking for a refund (if that is possible).

                  Pierre

                  Comment


                  • Pierre,

                    The errors you are seeing are common I'm afraid. The elevation is not very reliable, particularly when worn as a watch, and errors of 100s of metres between starting and finishing in the same place are common.

                    Regarding calibration - the unit does not re-adjust. It only calibrates when you press the start button near a saved GPS location at the start of an exercise.

                    There are many of us who are very disappointed. If you want a refund, get one whilst you still have the option.

                    Comment


                    • Option to disable barometric sensor?

                      Originally posted by CHESILBOY View Post
                      There are many of us who are very disappointed. If you want a refund, get one whilst you still have the option.
                      Indeed. From all the reports here I think we can conclude now that the hardware itself and/or the positioning of the vents for the sensor is at fault. There will be no firmware fix for this problem.

                      However, what Garmin could do in firmware, is to add an option to disable the use of the barometric sensor for altitude and revert to GPS (the way it works in all the other Garmin GPS watches).

                      I use altitude for two things:

                      1) During workout: Check my current altitude
                      2) After workout: Graph the elevation profile and calculate total climb/decent

                      GPS is perfectly fine for #1. It is rarely off by more than 5-10 meters. For #2 GPS does poorly, but most training software now overlay the two-dimensional GPS track on topographic maps and get reasonably accurate calculations that way. There are edge cases, such as bridges and on the edge of cliffs, and minor changes in elevation may not be measured, but for the most part the results are more than usable. And consistent.

                      In theory, a (calibrated) barometric sensor should be much better than GPS at both these tasks. But with the broken implementation in the 910XT, it isn't. Frankly, it sucks at both. The elevation charts are a joke. But with regards to use case #2 above I am no worse off than I was with the older watches, as GPS and the 910XT barometric sensor are both unreliable. So I continue to use software and topographically calculated elevation charts for my analysis. I didn't get what I hoped for and paid for (the expected improved measurements from a good barometric sensor), but otherwise no harm done.

                      However, with use case #1, I am now actually worse of than I was with the 305 and 310XT. The altitude readings are extremely unreliable. Where I used to be able to trust the watch to tell me how many vertical meters I had left to the next destination/peak/pass, I now have only a vague idea. I would be much better off I could just disable the barometric sensor.

                      If anyone from Garmin reads this, we implore you, please just give us a setting to disable the barometric sensor.
                      Last edited by NOREM; 08-22-2012, 01:17 PM.

                      Comment


                      • Originally posted by CHESILBOY View Post
                        Pierre,

                        The errors you are seeing are common I'm afraid. The elevation is not very reliable, particularly when worn as a watch, and errors of 100s of metres between starting and finishing in the same place are common.

                        Regarding calibration - the unit does not re-adjust. It only calibrates when you press the start button near a saved GPS location at the start of an exercise.

                        There are many of us who are very disappointed. If you want a refund, get one whilst you still have the option.
                        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.

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                        • I think, the GPS altimeter is often more accurate than barometrical altimeter, that is dependent on the weather and on quality of manufacturing of sensor. Thus I have question. How can I do automatic calibration of barometrical altimeter according to GPS altimeter during a training?

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                          • Next question. How I can set a display of the actual altitude from GPS?

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                            • Do you mean how do you change one of the data fields to show altitude? Check the manual for customizing the data pages. You set it just like any data field. I think the field is called elevation.

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                              • Originally posted by EKUTTER View Post
                                Do you mean how do you change one of the data fields to show altitude? Check the manual for customizing the data pages. You set it just like any data field. I think the field is called elevation.

                                I know to show an altitude from barometrical altimeter (Read my first question!), but I dont know to show an altitude from GPS. There is a page in Forerunner 610, where I can see actual coordinates and an altitude from GPS.
                                Last edited by DURACER; 09-19-2012, 10:12 AM.

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