Altimeter recordings while running
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Re: Altitude incorrect while hiking
Dear All,
hello, i have just received my SV couple of days ago. this is my first Suunto watch. before i was using Garmin and Coros. i have done couple of test runs on my usual tracks and i see deviations in altitude. i start and finish running in the same spot- at my home, where altitude is 42m.
First run showed i have started at 48m and finished at 38m altitude.
the second run showed i have started at 39m and finished at 24m altitude and 25m remained for the rest of the day until i did automatic calibration and it got back to 43 meters. below is the graph of second run altitude, here i ran 10km, turn and get back home the same way, therefore graph should be symmetric but it is not. any ideas why is it happening what to do to get accurate altitude measures? Thank you.
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@Tadas-Linge I live in the plains and it happens quite often to me. I suppose when there is not much difference in elevation FusedAlti did not come to play to correct altitude so only the barometer is used and in your case (just guessing) weather changed in the meantime. The few past days when pressure was very stable my elevation gain profile was almost spot-on. FWIW I am used to manually setting the altitude before every activity… (if you manually set altitude FusedAlti still always works)
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Never forget that native gps precision is :
- not a « one meter precision »
- latitude and longitude precision are better than elevation precision.
The Few elevation differences that you have between start and stop at low elevations like where you are is quite good !
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i have something similar when the altitude reading is not calibrated. Based on some posts from @Brad_Olwin I thought it calibrates the altimeter even after 5-10min of exercise and it corrects the initial data but I am not sure it works always right .
in any case , I would suggest you calibrate your altimeter in the beginning
Merry Christmas -
I’m a long time Suunto Ambit 3 user and recently upgraded to the Race. So far it’s been amazing and no complaints. I live by the ocean and yesterday went to stand at the beach shore to manually calibrate the baro altimeter to 0m. After going home the altimeter read 106m as I live on the 8th floor. The next morning my altitude was 86m. I assume the change is from the change in barometric pressure. Today I went for a trail run with about 200m elevation and half way through the run I got the storm warning alert despite it being a beautiful, sunny cloud free day. I now have the storm icon stuck on the watch face and my altitude is reading -51m. I’m really not sure what’s going on and or what to do?
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@Redbeard_ranger The storm alert responds to changes in pressure. Most of my storm alerts occur on sunny days as there is a large front moving in. Check the baro pressure for the time you were running, I suspect there was a quick drop in pressure.
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@Tadas-Linge I have noticed the same with my Race. What bothers me is that I have understood that Altifuse goes back and correct the whole activity, but obviously it doesnt correct it If its “close enough”. This is how I have understood it to work, dont know If it really is working that way though
I wish altifuse would just correct the whole activity no matter how little the difference is. What could be the downside with that?
Manually setting the elevation is fine when starting from home though
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@Iceman1
Correcting the altitude from which source?
From GPS?
Even if the difference is small?
It would mean to use GPS altitude as a real good value, always, and everywhere. -
@Mff73 Thats just how I have understood it to work, from reading on this forum. I could absolutely be mistaken and it would be good If someone could clarify this for me.
Does it not go back and correct the elevation from the beginning of the activity, when “calibrated”? -
@Iceman1
Yes, it corrects from the beginning, but it needs to have sufficient difference to decide to fix a baro value. It is probably more complexe and explained somewhere, but if GPS signal is good enough AND difference between GPS altitude and baro one is more than x meters, then, there is a correction. GPS altitude is not perfect but roughly not dependent to weather changes, while baro changes are more precise, but subject to change with weather during an activity.
Fused alti is this algo between all that.So 10/15m difference between start and end can just be the limit of the thresholds to trigger any fix.
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@Mff73 Thank you for explaining! So, If I set the elevation waaaay of before an activity, I will have a completely corrected elevation from the beginning?
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@Iceman1
Yes, but still based on GPS altitude value, which still may be 10/15+m off.
Which lead to the same result than doing nothing and let the watch adjust if it can. -
@Iceman1 go on a run / cycling / any outdoor activity with current altitude displayed in one of the fields. Note the value being displayed at the beginning and give it a glimpse once in a while. You should notice a moment in time that it gets corrected, i.e. from 110m to 123m at around 15 minutes from the start. It also works retroactively, meaning that the data saved to SA will be corrected from the start of your activity.
How often and in what way it’s being corrected afterward - I don’t know. Maybe some Suunto wizards will tell us more.
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@Łukasz-Szmigiel said in Altimeter recordings while running:
How often and in what way it’s being corrected afterward - I don’t know. Maybe some Suunto wizards will tell us more.
That would be interesting!
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@Iceman1 yes really interesting. Yesterday i went for a run, altimeter was calibrated manually before run to 41m and after 3 hours of GPS activity in the same spot i already had 68meters. So i do not see, how calibration helps here. Yes it shows the right altitude at the beginning of the activity, but then deviates. Maybe anyone knows some contact person in Suunto, who could explain in more details such measurements? Thank you.
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@Tadas-Linge You can certainly contact support but there are Suunto folks here on the forum. First, how about a few more details. The placement of the baro sensor holes on the Vertical have virtually eliminated issues with the sensor holes coming into contact with skin and changing pressure, which happened on the Suunto 9 baro.
- Are you wearing the watch under clothing or over clothing?
- Is it windy where you are running? Very strong winds can affect the sensor as well but they have to be strong.
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@Brad_Olwin hello and thank you for your answer.
- when i am running i always wear watch in such way that it would be exposed at all times, because i am checking it constantly.
- i cannot say it is windy. app shows that last time when i ran and got +25m altitude deviation at the end of run wind was 6m/s, but i could not say that there was any wind at all.
i have also a question is there any way to check if during activity watch is measuring altitude by baro sensor or by gps?
Thank you
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@Tadas-Linge it’s all the time mixing gps and baro. That’s fusedalti. Baro only if you use a sport mode where gps is not activated.
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@Tieutieu thank you for your reply.
yes, this is clear, but the question is how watch is determining that now i will use GPS and now Baro. and because i am seeing these deviations, i am assuming that at that time Baro was used instead of GPS. if yes, then why? -
@Tadas-Linge barometer is used by default for altitude with the exception of few sports where the wind is extreme.
FusedAlti is using gps for barometer calibration but in general, barometer is being used for altitude as gps is too unreliable for constant elevation measurement.
That’s why initial calibration happens in the first 15 minutes of workout as there’s quality threshold (the calibration won’t happen if the GPS error is too large).
GPS is fine to calibrate the barometer but it’s unreliable for constant altitude measurement.