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larkim Mar 2021 12:16pm, 19 Mar 2021 13,813 posts	0 larkim Presumably the problem with the barometric is that if it samples once every arm swing at the top and bottom, if you move it up 1200 times by 6inch over a 5k run it thinks you've gone up and down 1200 6in hills, so therefore you've climbed 600ft? If so, that algorithm looks duff! OTOH, the only barometric watch in my house records elevation really well!
azx Mar 2021 12:21pm, 19 Mar 2021 173 posts	0 azx My 945 is barometric too. This is from a 5k round a track last week:
Badger Mar 2021 1:08pm, 19 Mar 2021 13,657 posts	0 Badger I always chuckle at people who assume their individual experiences can be applied universally, but that's just me of course. With that caveat, I haven't seen anything like that level of error with a Fenix 5 or 6x. strava.com That's a flat 5k route logged as 59 feet ascent. Route plotting software with mapping estimates 92 feet. And for something a bit hillier: strava.com where the watch recorded 6234 feet of ascent and the race website says 6364 feet. The watch is clearly not exactly right, as the start and finish are close together and about 35 feet different in height but the elevation reading has shifted 150 feet down, so it's not doing a great job of compensating weather changes over the 7+ hours that took me. Perhaps the 645 has poor implementation? Both the comments about terrible elevation have been specifically about those units. Anyone got one where they are happy with what it records?
larkim Mar 2021 1:24pm, 19 Mar 2021 13,817 posts	0 larkim Presumably if pressure changes during a 7hr event there's nothing at all that a barometer on the wrist can do other than measure the pressure and convert that into an altitude, so drift like that would be expected - it doesn't know that weather has changed?
Badger Mar 2021 1:33pm, 19 Mar 2021 13,659 posts	0 Badger Well, there are two approaches to compensating that - there's tracking the GPS elevation, filtering it hard, and adjusting the barometric calibration when barometer and GPS are clearly drifting apart. Suunto did this on the Ambit range and frankly they were better in my experience than any barometric implementation Garmin have ever achieved (but for me Garmin won on balance for other features). The second is having an elevation map in the watch, which my F6x has. It nails elevation at the start of an activity. It's supposed to compensate gradually for weather changes as barometer and map drift apart, but clearly isn't doing very much. I should dig through the settings and see if there's anything more aggressive that can be done. I should note that it isn't using the DEM at every point, and nor should it, because the granularity of the map, and things like GPS errors turning into very large elevation swings if, for example, you're contouring on a steep hillside, or how location should be mapped to elevation if you could be going across or underneath a bridge over a gorge, introduce errors of their own.
larkim Mar 2021 1:49pm, 19 Mar 2021 13,819 posts	0 larkim Interesting, I'd never assumed they could / should do anything other than convert a certain pressure reading into a specific altitude. I can see how triangulating the various measurements could be used to aid precision though; having said that, I'd want to be standing next to a monolith on Tryfan and the watch sense the elevation change as I climb up it, and move 1m to the left without it smoothing it out to say they both had the same elevation because they were within the same area from a coordinate perspective.
Badger Mar 2021 1:57pm, 19 Mar 2021 13,660 posts	0 Badger Yes, those kinds of compensation work on scales of tens of minutes at least, and hundreds of metres horizontally - on the kind of fine scale you're talking about, pressure changes (filtered to remove effects as small as arm-swing) map straight to elevation changes, it's just the sea level pressure reference that should be gradually changing.
K5 Gus Mar 2021 6:18pm, 19 Mar 2021 4,423 posts	0 K5 Gus Going back to um's point on previous page regarding the change Fetch has made : since then the Weekly Altitude graph and the Monthly Summary infographic are no longer recording any altitude for watches with barometric altimeter. I raised a feedback and commented on the blog about 3 weeks ago.
The_Saint Mar 2021 7:03pm, 19 Mar 2021 6,772 posts	0 The_Saint The 645 and its barometric altimeter problems, people in my club said the same about the other models they had with a barometer, still I am sure this is a collective generalisation (sigh) forums.garmin.com forums.garmin.com forums.garmin.com
The_Saint Mar 2021 7:08pm, 19 Mar 2021 6,773 posts	0 The_Saint A random Cardiff parkrun with 334 metres of elevation change connect.garmin.com

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