Erratic Pace and Altitude mid-run

Not sure what happened. I was doing a track workout today. I didn't notice it during the run or intervals (4 x 1200), but after the run my watch showed an elevation gain of 1887 feet (running on a track)

It was fine/normal for the first 1.8 miles, and then everything went erratic.

beta 17.75 GPS 5.30

Anyone ever see this before?

Top Replies

silentvoyager over 4 years ago in reply to morey000 +1

It seems the pace started being noisy at the same time as altitude. Do you have 3-D speed enabled? I wonder if the pace was affected by the altitude changes?

But in general, pace is far from being accurate…
Bitti over 4 years ago in reply to silentvoyager +1

Also, heavy rain clouds weaken GPS reception, so that might at least partly explain pace problems during rain.

All Replies

0 5693709 over 4 years ago

there's been several threads on this, based on your altitude graph, but i don't know about the pace weirdness. One theory is after running about 20 minutes sweat obstructs the port holes that lead to the baro sensor, causing it to behave erratically. I've never had it happen while running, but I'm old, don't run very far, and don't sweat all that much. I did see it happen in real time on a river rafting run, if we ran a rapid and water splashed over my watch, the altitude reading would start bouncing around for a minute or two, and then stabilize again. Not sure if it happened every time it got wet, but I noticed it happened 2 or 3 times over the course of an hour or two just by randomly looking at it.

0 morey000 over 4 years ago in reply to 5693709

5693709 said:
One theory is after running about 20 minutes sweat obstructs the port holes that lead to the baro sensor, causing it to behave erratically

it was raining during the run. So- that's a good theory.
Which might explain the baro/altitude issue. but it doesn't explain the pace issue.

0 Dan.Boilermaker over 4 years ago in reply to morey000

Same here. I have seen wacky elevation readings during runs with heavy rain, but not in conjunction with pace issues. Since your pace and elevation issues coincide, I wonder if there was some other systematic issue going on. Maybe a power-off/power-on or soft reset may help?

0 silentvoyager over 4 years ago in reply to morey000

It seems the pace started being noisy at the same time as altitude. Do you have 3-D speed enabled? I wonder if the pace was affected by the altitude changes?

But in general, pace is far from being accurate on Fenix 6.

0 Bitti over 4 years ago in reply to silentvoyager

Also, heavy rain clouds weaken GPS reception, so that might at least partly explain pace problems during rain.

0 morey000 over 4 years ago in reply to silentvoyager

silentvoyager said:
It seems the pace started being noisy at the same time as altitude. Do you have 3-D speed enabled? I wonder if the pace was affected by the altitude changes?

I think you solved the puzzle! the altitude was erratic due to water in the pressure port, and the pace was erratic due to 3D pace.

FWIW, my data was all fine/normal on today's run.