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why using a barometric altimeter...

just trying to find myself an answer but without success. Why implementing a barometric altimeter in a running (triathlon) sport watch? Is a matter of fact that barometric altimeter is not as precise as a gps altimeter so why Garmin did use for top level sport watch this solution? Every day, several time per day I recalibrate my altimeter; I never wake up in the morning having the right measure and every night I recalibrate it to my known home altitude (51 m) and when I do it using the GPS I never have the same result and I need to manually enter these 51m and few seconds after it's already signing a different altitude (+/- 2 meters). As far as I remember my "old" 735 XT very seldom needed a recalibration..it was so accurate comparing to 935 that from time to time I regret I've sold it...
So, why? to whom the barometer is useful for some reason? I can live without barometer as I think the 99% of the runners out there....who cares of atmospheric pressure when you go out for a run or a ride or even a swim? it probably means something if you use parachute or you climb mountains...but the "Forerunner" series are made "For-runners" mainly and I'm sure we can barely find a runner interested in barometer...especially if this is affecting also altimeter measure or elevation gain...my suggestion for Garmin is to let the users choose whether using barometer or not
sorry for the outburst
Andrea

0 afarnedi over 6 years ago

In my view, apart from absolute altitude at beginning and end, altimeter based measurement is the way to go for you.
Do you happen to have a friend with GPS only watch?
Pick a track where you have continous up or down for longer time.
Take altitude at beginning and end and calculate delta.
Your watch should be closer to real heigth difference, then your friends one.

To just manage what to expect: if you ran the same track in the past using the 735 then you should see there is quite a difference.
To measure your effort the elevation gain/loss are more relevant than the absolute height.
So trying to find the correct setting for calibration is one option and the other one to ignore altitude.
It is irrelevant whether you start from 51m oder 200m, but it makes a difference if you get 500m gain where you should only have 300m

NOTE:If you need to adjust elevation gain and not absolute elevation, then you might have issues with your watch and may require Support to replace.
Would you mind sharing an un-edited activity?

what you mean exaclty when you say "finding the correct settings"? don't know what to do a part from calibrate height wherever I found a place with a known height...unfortunately calibrate the barometer with air pressure it's not as easy...I don't even know where to look for this kind of info that is reliable.
PS: don't know how to share activity

0 Steph74-74 over 6 years ago

First of all GPS altimeter is not precise at all compared to barometric altimeter in term of variation. You can calibrate at a start of run your altimeter with GPS altitude but depending on how much satellite do you have, the GPS altitude could be +/- 30 to 50 m.

a barometric altimeter has to be at first calibrated but after it isvery precise (+/- 1 to 2m) in term of altitude variation.
you are right depending on the variation of pressure, the indicated altitude will vary during the day (that is why you have to calibrate it).

I have many barometric altimeter (I am running in mountains :-) and to say the truth the barometric altimeter of the forerunner 935 seems to me very poor. I open a post on that because there is a lot of variation during the day compared to my other altimeters. I have perhaps a problem on my watch (I don't know if it is hardware or software issue ...).

So people that are hiking/running in mountains are very interested about altitude variations of the track. Denivellation is a big issue in mountains and I will be happier if the barometric altimeter of my watch would work better ....
The auto calibration feature is for me not working well. I did not understand when it was taking the GPS altitude to calibrate the barometric altimeter (start of race ??). it is not clear at all

0 OperationOne over 6 years ago

>>as a matter of fact that barometric altimeter is not as precise as a gps altimeter
I couldn't read beyond this point as I fell off my chair from laughter.

+1, couldn't read further :D I've been working with sub-centimeter GPS surveying for over ten years, and it's a matter of fact that GNSS vertical accuracy is worse than horizontal accuracy of a 1.5 / 2 x factor, by design. apply that to standard L1 GPS horizontal accuracy (+/- 10m) and see if a +/- 4/5m barometer floating values are good or bad (tip: really good)

0 mdietinger over 6 years ago

Andrea,

here is information how to configure altimeter setting:
https://support.garmin.com/en-US/?faq=fFqaolJqep3QqZY5UqOCa6

One important thing to note: you should make sure your watch is on the newest SW.
There has been some altemeter inaccuracies with 9.xx.
With I believe 10.70 things got better for me.

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