Altimeter watch accuracy

[Shafiq]

The thread first started in 2021, Nov. That makes it younger than it's 4th birthday. Still a toddler if you ask me

In terms of barometric pressure that I believe these altimeter type intruments use, 40m is pretty good going. I've always just reset the elevation on the device (be it a Suunto or various Casio Protreks) and am happy if I'm fairly in range.

The Wahoo gps device for some reason is alot more accurate than the watches I've owned. But, for uniformity (I probably view elevation slightly different from most people in the bwck of beyond as it's not necessarily safety critical, but rather for training purposes) I tend to click, 'use Strava elevation' after I've uploaded my ride/run.

Today my watch (Suunto 9 the non altimeter version, so I assume it was using gps for the calculations!) told me I'd run 850ft over a course of 6 miles. But resetting the data to use Strava elevation data, I got 910ft. Only 60ft (20m) off which is pretty good going. Also, I find that covering the sensor for the altimeter confuses the watch/Wahoo as does various weather types. Humidity etc etc...

 

[Jim_Parkin]

Bit of a thread hijack, but does anyone know of an altimeter watch which isn't also a big, chunky, battery guzzling GPS enabled device? I've been trying to do more "low tech" nav with map and compass recently, partly to be sure I'd still be confident with it if my GPS failed, and its very satisfying. I can absolutely see an altimeter adding to that, but it rather defeats the point if its only available as part of an all-singing all-dancing GPS enabled device - I want to have it as a "low tech" option for when I don't have GPS?!

My Garmin is perfectly happy as a watch with an altimeter when the GPS not turned on.

With 12 days without GPS if it's not sunny (longer with sun) it's not much of a battery hog. Garmin Instinct Solar (they have loads of different versions)

 

[JimH]

Plus one for Suunto.

You should update your altimeter when you're at a point of known height. If the stated height is going down each time the pressure is going up and vice-verser.

Definitely not a vote for my Garmin Forerunner 935, the barometric altimeter in this is pants (I believe it's a known issue with this and the Fenix 5), it currently thinks I'm 300m below sea level!

Calibrating it against a known height or GPS works for a while and then it drifts off again.

 

[WilliamC]

Definitely not a vote for my Garmin Forerunner 935, the barometric altimeter in this is pants (I believe it's a known issue with this and the Fenix 5), it currently thinks I'm 300m below sea level!

Calibrating it against a known height or GPS works for a while and then it drifts off again.

Yes, useless on the Fenix 5X Plus, fortunately solved on the 6X Pro.

 

[OwenM]

Calibrating it against a known height or GPS works for a while and then it drifts off agagain.

Yes if it's a barometer it will because the atmospheric pressure is in constant flex. That's why you need to keep calibrating them.

 

[WilliamC]

Yes if it's a barometer it will because the atmospheric pressure is in constant flex. That's why you need to keep calibrating them.

But neither the Fenix 6 nor the Etrex 30 share the problem. I never bother calibrating and they're always close enough for my purposes. The Fenix 5 is constantly way off, other than when very recently calibrated.

 

[mjh]

I wonder if on more modern Fenixes it is autocalibrating from the GPS? Or even using the GPS for height?

Owen is spot on that a barometric altimeter will always need regular calibration.

 

[Johnny3000]

Garmin watches autocalibrate altitude at the start of each workout.

 

[JimH]

Yes if it's a barometer it will because the atmospheric pressure is in constant flex. That's why you need to keep calibrating them.

I know, but this just drifts off at a rate you wouldn't expect, mine's set to auto-calibrate every night, but is very rarely correct. It's changed altitude by a couple of hundred metres this morning (and I haven't).

 

[Patrick]

I know, but this just drifts off at a rate you wouldn't expect, mine's set to auto-calibrate every night, but is very rarely correct. It's changed altitude by a couple of hundred metres this morning (and I haven't).

The difference in sea level pressure between a high pressure and low pressure weather system can easily be 60mB or so, which would equate to 600m of "altitude" change. Now you're not often going to switch straight from one of these to another overnight, but a 20mB change (the equivalent of 200m of altitude change) over 10 hours would not be unreasonable, particularly in the windy weather preceding an approaching low.

 

[WilliamC]

Maybe, but my wife has been wearing the Fenox 5X Plus, which has been way out over a whole multi-day trip while I've been wearing the 6X Pro, which has been very close to accurate, as has the Etrex. It's hard not to think that there's something not right about the Fenix 5.

 

[Johnny3000]

Perhaps altitude autocalibration is set to Off on the Fenix 5?

 

[WilliamC]

Perhaps altitude autocalibration is set to Off on the Fenix 5?

I've checked, and mine is set to On.

 

[Patrick]

Suunto Vector or Core , those are what I used to use in my alpine mountaineering days.

Plus one for Suunto.

You should update your altimeter when you're at a point of known height. If the stated height is going down each time the pressure is going up and vice-verser.

I bought a secondhand Suunto Core off of someone here and it still serves me well. The standard strap fatigued and ripped so and I replaced it with a nylon webbing strap off ali to which I attach a Suunto Clipper (tipped by another user on here) for quick bearing checks.

Thanks for these recommendations. A Suunto Core is on its way to me right now . Looking forward to playing with it!

 

[Tweaker]

Bit of a thread hijack, but does anyone know of an altimeter watch which isn't also a big, chunky, battery guzzling GPS enabled device? I've been trying to do more "low tech" nav with map and compass recently, partly to be sure I'd still be confident with it if my GPS failed, and its very satisfying. I can absolutely see an altimeter adding to that, but it rather defeats the point if its only available as part of an all-singing all-dancing GPS enabled device - I want to have it as a "low tech" option for when I don't have GPS?!

Check out g shock . The older ones that don't look like a dinner plate on a strap are my choice. Calibrate continuously when you get to know points say at the end of a leg.
Anyone who questions wether an altimeter is useful in the mountains has not done much time navigating outdoors.......

 

[Johnny3000]

I've checked, and mine is set to On.

Found this on another forum, somebody had similar issues with their Fenix 5, a reboot or reset helped.

Barometric Altimeters - Elevation maps way out! - fēnix 5 Series - Outdoor Recreation Archive - Garmin Forums

A dedicated community for Garmin users to ask questions, provide answers, and share feedback.

forums.garmin.com

 

[rob d 2]

Thanks for these recommendations. A Suunto Core is on its way to me right now . Looking forward to playing with it!

You'll be glad of this! I have a Suunto Xlander, a fancy version of the Core. Bought from a mate about 21 years ago. It's been fantastic, extremely accurate, but of course does need regular calibrating, esp in UK. Other areas are more stable.

Another use, which I expect you know: if you keep finding you're 'higher' than you really are, the barometric pressure is dropping - and vv. So you can use this info to help decide if a change of plan is required, maybe to get the hell out of here! This might be relevant if you're the wrong side of a river, and need to cross it while you can.

 

[Patrick]

You'll be glad of this! I have a Suunto Xlander, a fancy version of the Core. Bought from a mate about 21 years ago. It's been fantastic, extremely accurate, but of course does need regular calibrating, esp in UK. Other areas are more stable.

I've had it for a few days now. It actually needs calibrating less often than I expected - I'm impressed with the "auto" mode which switches between altimeter mode (when it senses rapid changes in air pressure) and barometer mode (when the pressure only seems to be changing slowly) automatically. This seems an effective method of making sure that it doesn't assume that (say) an overnight steady drop in barometric pressure is actually you climbing a mountain in your sleep!