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Altimeter performance test

Data
7 days ago

Update: Another day, another test, and completely differemt results. All three watches showing the same erratic drift. I should not have posted about results of only one test. The original text of my post is below here. 

I set the Sensor Mode to Barometer Only now and ignore the altimeter. The Auto setting just doesn't work very well while the weather is so variable. 

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I was running with three devices today (testing a repaired Fenix). The run is visible as the dip in the graph on the two Fenix-es. But what's up with the Forerunner? It seems random.

The FR955's altimeter was always climbing or descending steadily during sleep, but now it has lots of variation all during the day and night. As a result, the barometer graph is just a blocky thing that isn't easy to interpret.

I think this might be a bug.

  • 0 3 days ago in reply to Stefan

    The test setup was as follows: To compare the FR955 (worn 24/7) with two other watches:  around 19:00 I start wearing a Fenix 6X Pro and a Fenix 5 Plus on my other arm. Around 20:00 I go for a run, about 1 hour. Then I rinse all three under the tap, towel-dry them and put them on a shelf until I'm done showering, then put them all on again. At 23:00 I look at the altimeter and barometer graphs, make screenshots and take off the two Fenixes. 

    The first test showed markedly different behavior of the FR955, but after a second test all three showed nearly the same erratic behavior, wrongly attributing ambient pressure changes to altitude changes.I don't think all three devices are broken in the same way.

    I think the Auto setting attributes all ambient pressure changes larger than approx 1 hPa per hour, to altitude changes. And this behavior is common on more devices, although some probably have slighty different thresholds than others.

    Changing from Auto to Barometer Only solves this issue. I am happy to trade in altimeter functionality for a good barometer. 

  • 0 2 days ago in reply to Data

    Thanks for the description of your setup.

    But this seems fine. So in the next tests you could not reproduce the strange behaviour of the forerunner 955.

    I also encountered a drift in my activities - as I have written. And it is also pretty hard to filter what is the change in the ambient pressure and what is due to altitude change. Maybe they have some standard model of the 1hPa per hour - or nothing. But they could also work with weather models as long as the device is connected to the phone or to wifi at some point (what they probably don't do...)

    So for me the auto setting is working fine so far, but as you say it depends on the usecase. Nice would be if the altitude determined by the GNSS systems would also be logged in the files. Then you have at least a backup if you are interested.