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Elevation completely off

I did a very short run this morning and I had the elevation in metres going to absolute extremes of -77m. No mountains or hills and its all a flat run. What is going on?

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trux over 5 years ago in reply to dukeskd +1

Very sharp changes. I'd tell it could have happened for example if you wear the watch very close to the wrist - in such case, when you bend the wrist outwards, it closes the sensor hole, and can trigger…
trux over 5 years ago in reply to dukeskd +1

... or just move it little bit upper on the forearm, away from the wrist. It is usually better for the OHRM (Optical Heart Rate Monitor) anyway, in this way. Though, trying it on the right arm, just to…
fuzzy50 over 5 years ago in reply to dukeskd +1

Have you tried calibrating it with the gps

Menu, settings, sensors and accessories, altimeter, calibrate

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0 trux over 5 years ago

Likely sweat entering the pressure sensor hole. Browse the forum of the older Instinct (it has the same construction). There are dozens of threads discussing it, including many tips how to avoid it.

0 dukeskd over 5 years ago in reply to trux

I checked the watch through out the time and it was not wet. This to me indicates a SW issue or algo

0 dukeskd over 5 years ago

Here is an image of the activity

0 trux over 5 years ago in reply to dukeskd

Very sharp changes. I'd tell it could have happened for example if you wear the watch very close to the wrist - in such case, when you bend the wrist outwards, it closes the sensor hole, and can trigger a pressure shock on the sensor. Try putting it on the other hand, so that the hole directs away from the wrist.

0 dukeskd over 5 years ago in reply to trux

Hmm that could be the issue. I will move it from my left to right and see how that works out.

0 trux over 5 years ago in reply to dukeskd

... or just move it little bit upper on the forearm, away from the wrist. It is usually better for the OHRM (Optical Heart Rate Monitor) anyway, in this way. Though, trying it on the right arm, just to see whether it is indeed the reason, is certainly a good way to confirm or exclude it.

0 fuzzy50 over 5 years ago in reply to dukeskd

Have you tried calibrating it with the gps

Menu, settings, sensors and accessories, altimeter, calibrate

0 dukeskd over 5 years ago in reply to fuzzy50

That is a great suggestion, thank you. Opened up the calibration and it was set at -33 where it should be +4m. Let's see how it fares on my next run!

0 trux over 5 years ago in reply to dukeskd

Calibrating the altimeter is certainly a good idea, but there is no way an uncalibrated altimeter could cause this kind of elevation profile, without any other reason.

Auto-calibration "during the activity" could cause sudden changes in the elevation profile, but in such case it would not set the elevation to -77m (unless you are somewhere near the Dead Sea or at a similar location below the sea level). The negative elevation drop rather points to a sudden increase of the pressure - as I aready sugessted earlier, either due to the sweat (or dirt) entering the sensor hole, or due to the hand covering and pressing it.

It could be also due to wind gusts, or due to strong air flow during fast bike descents. Though, I would not expect as sharp drops as these ones. Protecting the pressure sensor hole with a sleeve or with a sweat wrist band at the side of the watch, would help excluding those factors.