Too much vertical gain and faulty barometer

Hi guys,

My Fenix 5x is going nuts lately.

Symptoms:

When I perform a roundtrip run the end altitude is way lower than the start altitude
The same hills look completely different during a run
Way too much vertical gain
Altitude graph shows downhill sections when there aren't any

Example:

#1 & #4 are the same hill I ran from each side
It's a roundtrip so altitude at start and end should be way closer
'Start' to #1 and #4 to "End' are the same route, but look way differently
None of the hills has downhill sections in reality

This behavior started roughly 3 weeks ago and I can see it on every run activity. Different weather is not causing this. I don't observe that problem when I strap my watch on the handlebar of my bicycle as well.

What I did so far:

Put the watch on diagnostic mode. Barometer is fine.
Rinsed the sensor hole gently

How do I fix this issue? And is anyone else observing this issue as well?

Daniel

0 Daniel_Ilg over 4 years ago

I figured out that some Fenix 6 are showing the same problem: forums.garmin.com/.../6x-sapphire---incorrect-altitude-recording-strange-altitude-profile-jagged

0 Daniel_Ilg over 4 years ago

Garmin - Chris

do you know anything about that?

0 razmichael over 4 years ago

Couple of things to try but first you should probably keep in mind that the hills are actually very similar in profile but before hill 4 you had a drop in "base" altitude of about 20m. This is actually not that much given the expected accuracy of the altitude ( https://support.garmin.com/en-CA/?faq=WlvNrOungC28xGtwB7hLY5#:~:text=With%20proper%20calibration%2C%20the%20barometric,accurate%20due%20to%20environmental%20factors. ). In addition, it does not take much change in air pressure to cause that amount of elevation change (it's about 2-3 hectopascals only). There seems to be a slight gradual drop leading to the bigger drop so, although unlikely, could be weather related. I'm just noting these things because your graph tends to look worse that it might be due to the scale (your base to peak is about 100m).

What are your calibration settings? I would try with auto-calibrate OFF to avoid mid run calibration that can cause this type of jump/drop and see what happens. Given the inaccuracy of GPS in the vertical, it only takes a section with less accurate GPS to mess up a calibration based on the GPS altitude. You can manually calibrate before you start the activity if you want but if your interest is gain/loss during the activity this does not really matter. Not really applicable IMO to compare the 5X to the 6 as the latter has more calibration options such ad DEMS data. The types of things they are seeing in the forum link do not really seem to be the same.

0 Daniel_Ilg over 4 years ago in reply to razmichael

Hi razmichael,

Unfortunately, it's not the weather. It pretty much worked with FW 19.10, and afterwards it got worse and worse. My standard route has now 180m vertical gain, whereas it used to be 110m for years.

I will try auto-calibration next.

I have DEM data at my 5x as well.

Thank you though!

Best regards

Daniel

0 Daniel_Ilg over 4 years ago in reply to Daniel_Ilg

I tried auto-calibration but it's not practical for me, since I need a calibrated altimeter during mountaineering. And I will probably forget to calibrate manually prior to an activity.

Will try altimeter mode in barometer settings next.

Daniel

0 Daniel_Ilg over 4 years ago in reply to razmichael

I tested just altimeter setting:

It got way better. The minimum and maximum are way closer.

Still see some drops in the uphill parts and hill #4 is still the same than hill #1

Might be checking wearing it on my other wrist.

Best regards

Daniel

0 Daniel_Ilg over 4 years ago in reply to razmichael

PS: here you can see the same track from June with FW 19.10

Way smoother and hill #1 & # 4 are way closer. No downhill sections during uphill.

0 Daniel_Ilg over 4 years ago

So, contacted Garmin Support. They said it's probably the sensor and they offered me a refurbished watch for 175 Euros.