Related
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Altimeter always showing negative overall elevation

leehunt
over 6 years ago
Hi all and apologies if this has been covered. I'm using a Forerunner 935 and constantly notice that when I head out on round-trip runs, that overall is shows massive negative drops in altitude over the course of the run, even if the run is completely flat (or close to it). I've attached a couple of Elevation charts from Garmin Express that you can see the negative trend. One of the worst was the elevation chart from the Chicago marathon that for those of you who know it, it's pancake flat, yet my Garmin reports that it looks like I was running downhill most of the way.

I checked out DC Rainmaker and tried submerging the watch in soapy water but that still doesn't seem to resolve the issue
* Has anyone else seen these drops in elevation on point to point runs?
* Is it because of the bad placement of the actual barometric altimeter air vent underneath the watch itself?
* Has anyone been able to resolve these type of issues?
* Can you even turn off the barometric altimeter so that it can rely on GPS data instead? ciq.forums.garmin.com/.../1382466.png ciq.forums.garmin.com/.../1382467.png
  • 0 over 6 years ago
    Hi leehunt , I have the same behaivor for months and until now, I have no idea to how fix it.

    I tried the soapy water solution too, and, like you, there wasn't help.

    The BEST option, and Garmin should take it in consideration, whereas all series of garmin's devices have some altimeter issue, is if we could choose on the watch if we want altimeter/barometer or GPS based elevation.
  • 0 over 6 years ago
    Curious to know if you found an answer? I'm on my 3rd 935 watch due to incorrect elevation readings and it's rather frustrating. One run had me starting, I would assume, at the bottom of the ocean. I've tried the soapy water and hard resets and no response from the watch. I finally emailed support.
    https://connect.garmin.com/modern/activity/2946094846
  • Former Member
    0 Former Member over 6 years ago
    One run had me starting, I would assume, at the bottom of the ocean.]


    This is because you're not calibrating your 935. GPS alone can have a margin of error + or - 400 feet. Your 935 has a barometric altimeter. Obviously, altitude will change with elevation gain or loss, but it will also change with changes with the barometer. You have 3 modes to select from. See the link post #3 this thread. "Auto" (the watch determines why the barometer changed), "altimeter" (assumes any barometer change is due to elevation change) and "barometer" (assumes any barometer change is due to temperature/weather). Because your barometer is constantly changing, frequent calibration is a must to remain accurate. I calibrate prior to every workout. If you calibrate prior to your run, you'll never have a run starting below sea level.
  • 0 over 6 years ago
    "calibrate prior to every workout"?
    i would have assumed that when you start a workout and GPS locks on that would then calibrate the altitude. Sadly this is not the case.
  • Former Member
    0 Former Member over 6 years ago
    It should, but keep in mind that Garmin states a + or - 400 foot error margin is acceptable.

    https://support.garmin.com/en-US/?faq=QPc5x3ZFUv1QyoxITW2vZ6

    My residence is a known 470'. Depending on the time of day, cloud cover, etc., I've had GPS readings anywhere from 200' to 650' at the same location. It's just the capabilities of the device and the GPS signal received at that time. On a clear day my GPS fix is within 10 feet. Calibrating prior a workout solves this problem.
  • 0 over 6 years ago
    "calibrate prior to every workout"?
    i would have assumed that when you start a workout and GPS locks on that would then calibrate the altitude. Sadly this is not the case.

    Actually, it is the case.

    But there are a few caveats. I can tell you how it worked in my F3. The 935 is probably the same, but you will have to check for yourself.:

    1. You need to have the auto calibration enabled.

    2. You need to have a GPS fix before you press Start in the activity. The watch will not auto-calibrate if it gets the GPS fix after you pressed Start.

    3. If the watch remembers an elevation from an earlier auto calibration or manual calibration at the same location, it will reuse that elevation, no matter if it agrees with the current GPS elevation.

    Especially item 3 can be confusing. But it can also be a help:
    Go outside, enter a GPS enabled activity and wait for a GPS fix. Then do a manual calibration of your altimeter while you still have the GPS running. From now on, you will probably see this exact elevation every time you start an activity at that location, no matter if the GPS suggests another, slightly wrong elevation.
  • 0 over 6 years ago
    Same problem here. Always negative total elevation. Tried all the forementioned “solutions”. Looks like a software bug to me.
  • Former Member
    0 Former Member over 6 years ago
    I can't confirm an issue for FW 10.10. I did a 30 km run yesterday with 200+ m total elevation with start/finish at the same point and got only +9 m altutude at the finish, which is very precise. Altimeter has been calibrated some months ago for the start location.