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Series 6 Altimeter - real world experiences

wilberforce

macrumors 6502
Original poster
Aug 15, 2020
387
297
I am contemplating upgrading from the S5 to S6, maybe for the brighter AOD outside, but perhaps also for the improved altimeter.
I do a lot of hiking and mountain biking, and elevation gain is an important metric for me. I use various tracking apps, including Workoutdoors (first class app), Apple workouts, GaiaGPS (on iPhone), bike computer, all of which track elevation gain, but it is sometimes a bit inconsistent.
Does anyone have any real world experience using the S6 and does it really provide improved elevation gain tracking, over S4 or S5?
I am interested in the elevation tracking improvements, not in constantly watching an altimeter.
I understand that the S6 altimeter is improved accuracy and always-on, but does it translate into better practical use for hiking/biking?

Apologies if this question has already been asked, thanks
 

dallison13

macrumors regular
Sep 10, 2014
127
83
I use most of those same apps and do similar activities. So far with the S6 (had an S5 before) I haven't noticed a huge difference yet.
I notice that it seems all over the place however. I use a Stryd Pod for running sometimes with the Stryd app and the elevation will be spot on with my Garmin one day on a trail run then different on a relatively flatter road run. Who knows.
Ran an Interval track workout today with Intervals Pro and the Workout App and the elevation was off by a whopping 300 feet. What?
So, I think it has some quirks right now.
I just think the only advantage is if you are viewing it at that moment, it changes instantly on the complication or Compass app. However, in recording of activities, it works the same as before; which wasn't bad before.

edit. I just checked elevation and it was actually Strava that screwed up the elevation. Watch was spot on.
 
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michaelb5000

macrumors regular
Sep 23, 2015
147
78
I would have upgraded anyway (from a S3), but the always on altimeter is one of the key best features for me too. I haven't gone on a hike or a ride on anything that involves climbing yet, but I have tested this each day. I would say the S6 is significantly better at tracking elevation. This may mostly be when not running a workout, like "outdoor hike", that turned on elevation tracking as part of the workout, on the older models. So for me, with Workoutdoors, I would get pretty accurate tracking of total elevation climbed when I did hikes. But turning on a workout impacts the battery, so the big change with the S6 is you can view elevation continuously on the face of the watch as complication, and it updates promptly, so every few seconds at the slowest, without the battery hit of tracking a workout.

The watch doesn't store elevation gain in the health data. But it does track Floors Climbed. I try to climb 25 floors a day as a goal, and have for the past several years. I have a steep hill in our woods that is about 35 feet of total climbing. So I should get 3 floors every time I climb it. It is steep enough that the top and bottom are close in distance, so within the margin of error for GPS position (so GPS alone can't really track if I am at the top or bottom or moving between). So tracking the elevation change is entirely based on the altimeter. This is a lot like climbing stairs in a stairwell, back when I used to go to work. The S3 had a hard time tracking the tops and bottoms of the hill climb (or stair climb) as I turned around and changed direction, and would "smooth" out this elevation change; in WODs you can see this smoothing if you run hills since it draws an elevation profile graph.

So I have only had the S6 for week, but I have probably already done the hill 50 times over this past week (using various tracking workouts and also without any workout), and as best I can tell it has counted every single hill climb correctly.
 
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Born2Run

macrumors member
Nov 27, 2010
69
107
Brighton
The altimeter on my S6 seems to be wrong now... Since getting the watch its been telling me that my apartment is 34m but since last night its suddenly says it's 86m!
Could the change in temp or weather affect it?
 
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cdcastillo

macrumors 65816
Dec 22, 2007
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The cesspit of civilization
I never checked on the series 5 nor on the series 4. However, I happen to know there is an altitude difference of about 320 meters between my apartment and work. The series 6 shows a 326 meters difference. The higher margin of error at work might be related to the office being in a basement.

IMG_0358.jpeg
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chrfr

macrumors G4
Jul 11, 2009
10,193
3,911
The altimeter on my S6 seems to be wrong now... Since getting the watch its been telling me that my apartment is 34m but since last night its suddenly says it's 86m!
Could the change in temp or weather affect it?
Altimeters work on air pressure, so when the weather changes your altitude will change. I assume that the watch will correct itself with GPS data periodically.
 
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StumpyBloke

macrumors 68030
Apr 21, 2012
2,722
2,289
England
My series 6 is all over the place. In my home it varies from 86 m to 93 m sat in the same place. Pretty useless in my opinion. It often is quite different to the my altitude app whether that is using the altimeter or location data.



 
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michaelb5000

macrumors regular
Sep 23, 2015
147
78
It seems like we are confusing what an altimeter does here; or this is much more complicated than I think. An altimeter does not know your initial position in terms of altitude. An altimeter is a calibrated barometer, that displays change in pressure in the form of a change in altitude. So, in simple terms, if you are not moving and talking about a change in your elevation over time and distance, you may not be using the altimeter. For the most part, your initial position is determined by GPS (and maybe cell tower and wifi), on your phone or on your watch. So error in initial position is most likely GPS related. GPS is not very accurate in terms of elevation, so GPS related error in initial position can be significant. So the reading for your elevation at any given moment in time may be coming from the GPS and not the altimeter; the altimeter is measuring the change from whatever it was before.

Now the complicating factor is that the watch has "always on" altimeter. The older watches also had altimeters. My watch always has power and is on continuously (including when charging, the altimeter could be tracking changes?). So there it is possible that once the watch is powered and once the phone and watch have a good GPS fix on your position, the altimeter could be continually tracking your elevation and could do that mostly accurately (including possibly adjusting for weather related pressure changes). For me, my position at home has been locked in to a value + or - about 10 feet, day after day; even when it says the error factor is 100 feet or more. So I have been seeing very stable initial position elevation.

But, if I flew somewhere, or just drove up 1000+ feet to a trailhead, I still believe that the computer logic between the GPS and altimeter sensor in the watch/phone would adjust the altimeter based on GPS location (this is how my Garmin worked explicitly; so the altimeter was automatically calibrated via GPS, but you could also set it manually; I have an altimeter app on my phone and watch, and that also lets you adjust altitude manually if you know your initial position).
 
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StumpyBloke

macrumors 68030
Apr 21, 2012
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I really don’t understand any of this but that doesn’t explain why it can vary massively from app to app and hour to hour in the exact same location.

Sat in the same place and in space of two minutes my reading has gone from 87 m to 85 m.

Sat in the same place again, if I move my arm up or down both the built-in app and the my altitude app do register a change in height. I wonder how that works then. Both of these readings by the way are indoors.
 
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claude512

macrumors member
Jun 28, 2018
33
22
Altimeters don’t measure elevation, they measure barometric pressure.
So they are highly dependent on calibration, and very susceptible to weather changes (weather actually defines/changes current pressure, it’s the weight of the air mass above a specific point).

In addition pressure lapse rates are based on an average normed atmosphere (called ISA, defined by 1013.25 hPa at mean sea level at a temperature of 15C and 0% humidity; lapse rate then is averaged to ~1hPa/8m up to 5000m, then it halves).

Change any of the ISA variables (it is very rare to have exact ISA values in the atmosphere at any one position) and the whole thing becomes a constant source of issues (there are fotmulas to adapt vs ISA, but ISA is an abstract construct to start with).

So this does 2 things:
- on a properly calibrated altimeter (through a known elevation), shifts occur due to weather pressure changes (explaining a perfectly still watch going from 85 to 87m)
- going up (or down) an exact calibrated distance an altimeter will not usually show that elevation change exactly due to atmospheric structure different than ISA

All-in-all then, altimetry is complex, and without a way to calibrate (through either entry of a calibrated to MSL pressure, or a known elevation), readings will be an approximation/guess and fluctuate more or less wildly

Fun fact: airplanes (who you’d think are very reliant on altitude) NEVER know EXACTLY the altitude at which they fly.
Either they use a current pressure value adjusted to MSL at an airport (but then the instrument is calibrated to ISA so it shows wrong values and needs to be corrected if you need an accurate altitude, or above a certain level they all use the same standard value (objectively wrong but the same for everybody)

Having fun yet? 😂
 
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wilberforce

macrumors 6502
Original poster
Aug 15, 2020
387
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So I appreciate all the feedback and discussion from everyone. Yes, determining absolute (true) altitude is tricky, as a barometric altimeter does not know its true altitude, which has to be determined by other means, but it should be quite good at determining changes in altitude.
Fortunately, I do not care about my true altitude. I only care about relative elevation gain/loss on a hike or bike ride. But right now, with my S5 or iPhone or bike computer, my total elevation up often does not equal my total elevation down when I return to the same spot after an hour or two, and sometimes I see elevation gaining when it is actually level. It is not greatly off, but would be nice if the S6 is improved, and thus maybe worth upgrading.
I see reports that the GPS tracking in the S6 is improved over S5 (does not round off corners as much), just wondering if the elevation tracking is also improved by the improved barometric altimeter. Probably hard to determine without doing a series of parallel tests.
I think by itself this altimeter is not worth upgrading to S6. Anyone see it differently? I don't hear anyone saying: wow, this S6 altimeter is great!
 
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claude512

macrumors member
Jun 28, 2018
33
22
I’d agree, not worth upgrading just for the altimeter!

BTW Garmin have continous problems with altimeters too (I have the exact same problem as you, Garmin MARQ which uses the same firmware as the Fenix 6 so that will be the same also)
 
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Monkswhiskers

macrumors 6502
Feb 6, 2018
321
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I just use my series 4 altimeter as an 'as near as damn it' reading so I know how much climbing I have done on a bike ride. I then upload to Strava which corrects to their data which I assuming uses gps against mapping. What use an always on altimeter is beyond mountain climbing I'm not sure and then presumably you would want something a bit more robust than an AW.
 
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zhenya

macrumors 604
Jan 6, 2005
6,744
3,363
I’m not exactly clear what Apple has done differently in the AW6, but I suspect it’s mostly that they’ve just made the readings in real time, and applied some averaging to smooth the data, possibly included some referencing against location, etc.

The issues with a barometer which simply measures air pressure have been well described here. Even still, I find my Garmin watches with a barometer to overall give much better elevation data than you can get from GPS alone. GPS is much worse at measuring elevation change, as that z-axis data is so small at the distance a satellite is from the Earth that it’s almost imperceptible. All Strava is doing when it “corrects” your data is using their GPS database. There is a setting somewhere to turn that correction off, and if you have a good altimeter, I’d suggest doing so. The threshold at which GPS detects elevation change is, I believe, 30’. You see this in some people’s Strava activities - say an urban runner without many options for hill training does a bunch of repeats on a set of stairs or a small hill in a park - if it’s under 30’ Strava will report the total elevation (no matter how many repeats) as zero.
 
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Monkswhiskers

macrumors 6502
Feb 6, 2018
321
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I’m not exactly clear what Apple has done differently in the AW6, but I suspect it’s mostly that they’ve just made the readings in real time, and applied some averaging to smooth the data, possibly included some referencing against location, etc.

The issues with a barometer which simply measures air pressure have been well described here. Even still, I find my Garmin watches with a barometer to overall give much better elevation data than you can get from GPS alone. GPS is much worse at measuring elevation change, as that z-axis data is so small at the distance a satellite is from the Earth that it’s almost imperceptible. All Strava is doing when it “corrects” your data is using their GPS database. There is a setting somewhere to turn that correction off, and if you have a good altimeter, I’d suggest doing so. The threshold at which GPS detects elevation change is, I believe, 30’. You see this in some people’s Strava activities - say an urban runner without many options for hill training does a bunch of repeats on a set of stairs or a small hill in a park - if it’s under 30’ Strava will report the total elevation (no matter how many repeats) as zero.

Ah I see, thanks for clarifying. For info, I tend to ride the same route over and over and the elevation data is never too far out within a range, so whatever the 4 does it is fine for me.
People want the moon on a stick these days and get upset about eg. gps accuracy not being bang on etc. but if you think about how much the AW does for its size it is quite remarkable. There will always be compromise in such a small device compared to standalone dedicated instruments.
 
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StumpyBloke

macrumors 68030
Apr 21, 2012
2,722
2,289
England
Well my altimeter has died on me. I was getting some absolutely ridiculous readings whilst out on a walk with perfect phone signal and GPS availability. It was showing me 118 m incorrectly and did not sort itself out. I restarted the watch and the Apple complications and compass app now don’t register the altimeter at all.

The my altitude app still does so I don’t know if that gets data from GPS but that’s always been incredibly accurate.

Sending the watch back for a replacement.




 
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StumpyBloke

macrumors 68030
Apr 21, 2012
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On this thread, four peoples altimeters on the series 6 have failed on the same day. Apparently it’s a software issue. Any of you with a series 6 might want to see if you’re still works.

 
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Born2Run

macrumors member
Nov 27, 2010
69
107
Brighton
For the last few days mine was going between 84m and 260m in the same spot in my flat as well as '---' for long periods too!

I re-paired my watched and set it up as new, which seems to have fixed it for now and it's been at around 34m all day today!
 
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wilberforce

macrumors 6502
Original poster
Aug 15, 2020
387
297
For the last few days mine was going between 84m and 260m in the same spot in my flat as well as '---' for long periods too!
This may be because it cannot calibrate the barometric elevation against GPS elevation, as GPS reception is often poor inside. If the GPS antenna can only pick up a few satellites, it first loses elevation accuracy rather than losing location accuracy. Three satellites are needed for position, a fourth satellite is needed for elevation, and greater than four satellites increases the accuracy of position and elevation.
If you get such high variation outside, that would be more cause for concern
 
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Born2Run

macrumors member
Nov 27, 2010
69
107
Brighton
This may be because it cannot calibrate the barometric elevation against GPS elevation, as GPS reception is often poor inside. If the GPS antenna can only pick up a few satellites, it first loses elevation accuracy rather than losing location accuracy. Three satellites are needed for position, a fourth satellite is needed for elevation, and greater than four satellites increases the accuracy of position and elevation.
If you get such high variation outside, that would be more cause for concern
I did test it and it stayed around the 260m mark even when I went outside and walked downhill towards the sea.
 
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