Ascent measurement lag

peegee

I do a lot of trail running with a friend with a Garmin, we run the same trails at the same pace, he always gets a higher ascent than I do, this can range from 10m to up to a hundred meters.
On our last run I we both did a little test to try to get to the bottom of it.
We both ran up a short ascent of approximately 10m.
My watch showed a total ascent of 231m, my Garmin friend had 252m - prior to the test.
We ran up and down this hill 3 times and my watched still showed 231m - no ascent at all!!! My friend got an extra 26m which rose accordingly during the test.

I’m in performance mode with data logging every second,
So to my understanding it should show the climb of 10m on the spot.
I find this very annoying, that I don’t get a realistic reading! Does the Suunto have some kind of minimum height restriction?!? Or is there some other reason for this annoying phenomena?

sky-runner

@peegee There is definitely a threshold for increasing the elevation gain (ascent), but it is supposed to be 3 meters. It used to be 10 meters for watches without barometer, but I would be very surprised if 10 meter threshold is used in Race 2. That would definitely be wrong!

I think there is also some sort of rolling averaging of the current altitude so if you very quickly climb 10 meters and immediately start descending the altitude captured by the watch may never reflect the 10 meter increase. This may change if you wait at the top for a few seconds. If you do these experiments again, I recommend customizing the data screens so that you see the altitude side by side with the ascent. That will let you see exactly how the ascent changes over time when the altitude changes.

peegee

@sky-runner
Thank you so much for your explanation.
I never knew that there is a 3m threshhold…
Do you know why it isn’t a one meter threshhold?
I wonder what ithe threshold is on the Garmin, I imagine it is 1m according to the comparison I made with my running partner.

Regarding the test we did it is logical what you said, next time I’ll pause at the peak

sky-runner

@peegee The threshold is to prevent excessive ascent accumulation from changing air pressure, for example when swinging arms or when there are wind gusts, however even with 3 meter threshold strong wind gusts may still register as altitude changes. From my experience, Garmin threshold seems to be 5 feet or 1.5 meters.

But even with the 3 meter threshold, what you’ve observed is clearly wrong. As I recommended above, try the following:

Create a custom sport profile where you have altitude on the same screen next to both ascent and descent. I have that in my trails running profile - these three metrics and vertical speed as well.
During a trail run watch all the fields together. You’ll see that the altitude changes more smoothly. Because my watch is configured in imperial units I can see the altitude changing with 1 foot accuracy, which is 30.5 cm. But then you’ll see that ascent and descent fields change less frequently in large increments.

Audaxjoe

@peegee I ride a bike, I could go out with 10 people, often with the same make and model of GPS and we get ten different altitude gains.

maszop

@peegee This doesn’t make sense, as no watch measures altitude, only pressure changes.
A slight breeze, a sleeve, a few drops of water near the barometer sensor, and the results will be completely inaccurate. Lowering the threshold any further would be a disaster as soon as the weather ceases to be ideal.

peegee

@Audaxjoe
Yes that is often the case.
But as I mentioned the problem is with the the non measurement of ascents, which was explained in one of the responses.

peegee

@sky-runner
Thanks I will try this out