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The barometric altimeter

Hi all,

Is there a way to disable the barometric altimeter and use GPS only for elevation? Having owned the 645 for 3 months, and replaced it once already, I've concluded that the barometric altimeter on the 645 is useless and it just messes up the elevation of my activities. I have to go into Strava and correct the elevation every time. There is too much noise in the data, and after a 2 hour walk the changes in atmospheric pressure will result in significant drift in the accuracy of a calibrated altimeter.

Just to demonstrate the point, I did a 5 mile hike on Saturday, overnight camp, and returned via the same route the following day.

This is the outward leg:

https://www.strava.com/activities/2018727560

This is the return leg (after correcting the elevation on Strava with mapped data). Note that the start point is 20m different from the end point of the previous activity).

https://www.strava.com/activities/2020284554

On a side note, apart from the altimeter, the 645 great for orienteering. The electronic compass works very well and I found the watch reliable and accurate for basic navigation using waypoints, as I discovered during a very foggy weekend on Dartmoor. Certainly it's as good as the Fenix 5 in this regard.

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0 Former Member over 6 years ago

I have a 645 as well and I would say that the problem with the Barometric altimeter isn't its absolute accuracy, it is what is done with the data it records, I think it overcounts change in elevation somehow but it does it very repeatably, I run two different 4 mile routes regularly that both have a hill in them and it reliably gives the same readings for both (about 210 metres total climb uncorrected and about 80 metres corrected in Connect).

0 scotthunter2 over 6 years ago

So why isn't Garmin doing something about it? They seem more interested in telling us about gimmicks like Spotify support instead of working on addressing the fundamental problems with the watch. It's been out for almost a year now so there's no excuse.

0 Former Member over 6 years ago

scotthunter2 I don't have a 645. Does it have the option to set the barometer mode to "auto", "altimeter", or "barometer"?

0 scotthunter2 over 6 years ago

scotthunter2 I don't have a 645. Does it have the option to set the barometer mode to "auto", "altimeter", or "barometer"?

Nope - you can calibrate it, but that’s it. Once calibrated though, after a couple of hours it will be out and needs to be calibrated with GPS again.

0 Former Member over 6 years ago

scotthunter2 Perhaps you and others can request that Garmin add the barometer mode feature.

Different Barometer settings

Auto (default setting): The watch will monitor changes and automatically switch between altimeter or barometer modes
Altimeter: The watch is locked in altimeter mode and all changes in pressure will impact the elevation reading
Barometer: The watch is locked in barometer mode and all changes in pressure will be considered due to weather and changes in ambient pressure

What's happening is after you calibrate, the 645 goes into "auto" mode. This mode is basically guessing on why the pressure changed and then makes adjustments. Sometimes it works well, but most of the time it's just terrible. I live in the Puget Sound region where 35 miles east of me is Mount Rainier at nearly 15,000 ft and a few miles west is the Sound at sea level. In between is a bunch of up's and down's. I'm surrounded by the Cascade and Olympic Mountain ranges. Depending on which is stronger, weather fronts come in from the warmer California coast or the colder Alaska coast. All this means is actual elevation and rapid pressure changes are the norm and it wreaks havoc on my watch if in "auto" mode. I have found that depending on the weather or terrain I'm doing an activity in, if I select either "altimeter" or "barometer" mode, I don't have the problems you're having and it actual works extremely well. Garmin took away and then returned manual calibration of the altimeter with the 645. Maybe if enough people request the barometer mode feature Garmin will add it in a future update.

0 scotthunter2 over 6 years ago

This would make sense. I don't understand why Garmin would take away the mode selection and effectively render the altimeter useless in most situations. I know they omitted a few features from the Fenix line so that people would not buy the cheaper 645 for hiking and stuff, but in doing so they have crippled an important part of the watch's function.

I wish Garmin could wake up and read this - this is not the first time this issue has been raised yet they seem more focused on updating the music player.

As I've said before, the 645 is actually remarkably good as a navigation aid for hiking. The orienteering capability of the watch isn't talked about much as most people who buy this watch are runners only. It's just a shame that the dodgy altimeter lets it down.

0 Darren-M over 6 years ago

This would make sense. I don't understand why Garmin would take away the mode selection and effectively render the altimeter useless in most situations. I know they omitted a few features from the Fenix line so that people would not buy the cheaper 645 for hiking and stuff, but in doing so they have crippled an important part of the watch's function.

I wish Garmin could wake up and read this - this is not the first time this issue has been raised yet they seem more focused on updating the music player.

As I've said before, the 645 is actually remarkably good as a navigation aid for hiking. The orienteering capability of the watch isn't talked about much as most people who buy this watch are runners only. It's just a shame that the dodgy altimeter lets it down.

My wife's new 645M locked the altitude at -226 ft, which is a 246ft error. Is this common for the 645M? Surely not as that makes it not fit for purpose, especially in the hills!

0 Former Member over 5 years ago

I have the same problem with the Forerunner 645. Is there already a solution for this problem? Will there be an update from Garmin??

0 Former Member over 5 years ago

I bought this watch instead of the 245M because of the barometric elevation. My wife and I just hiked in Maine and the reported elevation from my watch was over 500 feet more than the stated elevation for the mountain we climbed. I'm OK with 20 or 30 feet, but 500? The weather was stable all day so I can't see where that had any effect.

0 Former Member over 5 years ago

Last week I went skiing in the Alps, at the altitude of 2600m my forerunner 645 indicated that we were at 3325m. That's a difference of more than 700m!! The weather was stable and the altimeter was calibrated in the morning. I can understand that there may be a slight difference, but this is really too much and completely unreliable. This wouldn't be allowed for this money?! When does Garmin come with a proper solution/update? Or any tips?