Series 3 GPS Accuracy

Discussion in 'Apple Watch' started by wittyphrase, Sep 30, 2017.

  1. wittyphrase macrumors regular

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    #1
    Has anyone else felt their watch’s GPS is less than stellar? I’ve used both my Apple Watch and Garmin 235 for all my runs this week. I know the actual distance of the routes and the Garmin is always spot on. On every run the distance measured by the Apple Watch and the pace have been off. It’s been off +.16 miles on shorter runs and got as bad as +.62 miles by the end of today’s run.

    I love the watch, but I’m fairly disappointed with this particular function. Is there any chance it’s the Apple Workout app and not the watch itself? Any settings I can/need to tweak to fix this. Might I just have received a lemon and I should try to exchange it?
     
  2. deadworlds macrumors 65816

    deadworlds

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    Citrus Heights,CA
    #2
    How long have you had the watch? I think that it needs 30 minutes of an outdoor workout to calibrate the distance. This was true back with the S0 watches and require that you bring your phone along.

    I’m not too sure about how it works now that they have a gps built in.
     
  3. wittyphrase thread starter macrumors regular

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    #3
    Had it for a week. Used it for 27 miles. Do I need to specifically put it into this calibration mode?
     
  4. deadworlds, Sep 30, 2017
    Last edited: Sep 30, 2017

    deadworlds macrumors 65816

    deadworlds

    Joined:
    Jun 15, 2007
    Location:
    Citrus Heights,CA
    #4
    No my old watch just said to start an outdoor workout for at least 30 minutes. Again I’m not sure how this process works now that GPS is built in.

    Found this: https://discussions.apple.com/thread/7836114?start=0&tstart=0

    And this:

    “f you have Apple Watch Series 2 or later, that's all you need to do. Your watch has built-in GPS, which allows you to get accurate information during an outdoor workout without your paired iPhone”


    How to get more accurate data:

    https://support.apple.com/en-us/HT207941
     
  5. edhchoe macrumors 6502a

    edhchoe

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    Oct 28, 2011
    #5
    .62 miles in 5 miles would be 12% error. That is terrible!
     
  6. lpb macrumors member

    lpb

    Joined:
    Jul 26, 2013
    Location:
    Sweden
    #6
    There is no need to calibrate the series 3 beacuse of the built in GPS. Series 0 and 1 needs to be calibrated with phone GPS to get more accurate.

    Have you tried another running app, like Runkeeper or Strava to see if it gets more accurate?
     
  7. deadworlds macrumors 65816

    deadworlds

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    #7
    See I at first thought that it wasn't necessary to calibrate the watch either, But in my watch app ( I have series 3 AW) theres an option to clear fitness calibration data. So it gets calibrated somehow.
     
  8. lpb macrumors member

    lpb

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    #8
    Yes, I think that when you doing a GPS activity on the watch it calibrates your stride length when walking or running without GPS on...
     
  9. wim.v macrumors member

    wim.v

    Joined:
    Jul 13, 2011
    #9
    I ran with the Polar M400 for over a year and I also noticed the AW3 GPS data is not accurate...
    My first test was with the Strava app on a 900m long running track. Laps varied from 700-900m. Polar M400 was always spot on.
    Yesterday I did a test run with the Workouts app from the apple watch on one hand and the Polar M400 on the other... Polar M400 registered a run of 5600m and the Apple watch 5410m.
    Heart rate measurements were the same on both devices.
     
  10. deeddawg macrumors 604

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    Jun 14, 2010
    Location:
    US
    #10
    Just curious - what's your data source for the route distances?

    I've been running with various GPS watches for years; FR610, FR920xt, Fenix3, FR235, and AW2 for the past year. I've done a lot of runs with my AW2 and FR235 at the same time, one on each wrist. Differences between the two have varied, typically in the 1-2% range with no consistence of which read more or less than the other. Well within the slight differences from autopause (gotta cross a number of streets on my routes).

    One thing I do which you might try - since the AW2 has no indicator of getting GPS lock, I just make sure it has a good 30+ seconds to solidify the fix before I start out. So once I'm out in the driveway or out of the office building, I start the run in the NikeRunClub then immediately pause it before starting up music and stretching a bit.

    All that said, it's always possible the watch has an issue or just isn't good for your environment. After a handful of wide variations in distances when I was seeing if I liked my Fenix3 (against my 920xt I think), I returned the Fenix3. Examining the tracks showed some really loopy position fixes when near office buildings, but the other watch didn't suffer from those problems. Haven't had any issues with my AW2 though, it's been pretty much spot on.
     
  11. wittyphrase thread starter macrumors regular

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    New York
    #11
    I’ve checked my routes using the course creation on Garmin Connect, Google Maps, and my car. Also lived in the area for a while somI’m fairly confident about the actual distances involved. That’s a fair point about the GPS lock. Are you starting the activity but just standing still with it? I’m not racing for world records so I don’t mind adding 30 seconds to my time if that’ll make the rest of the run more accurate.

    I have definitely been walking downstairs to the end of the driveway, pressing start and going. That’s fine for the Garmin since it doesn’t have to worry about the handoffs from Bluetooth to WiFi to cellular. Maybe thats part of the problem? If it remained at a .1 - .15 difference the way it is for the first few miles I wouldn’t care, but more than half a mile is a lot.
     
  12. deeddawg macrumors 604

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    #12
    Even my FR235 takes 10-20 seconds to firm up its GPS lock.

    I walk out then start NRC and immediately pause it, so maybe it logs 2-3 seconds. By the time I select a podcast and do a little bit of static and dynamic stretching (nothing fancy or major, just shaking out cobwebs of office work) the watch has had plenty of time and off I go.

    Which app are you using? Consider grabbing the RunGap app and uploading a watch run to Garmin Connect and comparing to the FR235. Zoom into the tracks and that should help you see what's going on.

    It's also possible you got a "bad copy" or something. While my experience above has been with a series-2, I'd expect the series-3 to be as good or better. (though Garmin's made strides backwards with new models, so it's possible Apple could too).

    Best of luck.
     
  13. wittyphrase thread starter macrumors regular

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    #13
    Thanks for the thoughts/tips and the RunGap suggestion. Actually sounds like something really useful so I’m anxious to try it out for tomorrow’s run.
     
  14. DynaFXD macrumors 6502a

    DynaFXD

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    Jun 15, 2010
    Location:
    East Coast
    #14
    Out of curiosity, is this running route tree lined? Big tubes of water (i.e. trees) can inhibit the signals of the wavelength that GPS uses. Which is one reason they aren't the most reliable things in woods and surveyors will often go "old school" to get points located in wooded areas. Second, how straight is this run? Lots of twists and turns?

    Tracking software that use GPS are not necessarily getting a constant stream of X,Y locations. Even very good tracking systems use Kalman filters and data from the GPS subsystem to figure out where it was, where it is likely to be now, and where it will be in the future (wash, rinse, repeat). They base this on polling data from the GPS subsystem. Polling the GPS can impact battery life big time. For instance, Waze will burn through my iPhone battery in about 2-3 hrs. As such, some portable devices/software will try to minimize polling the GPS to maximize battery life. If you are going in a straight line under open sky, it works just fine. If you are running a twisty route under trees, then the software may start trying to spline curves around its fixed locations and error in distance estimates will increase. Or, it just doesn't have the computational resources, possibly limited by battery life concerns, to resolve a solid way-point for its path finding algortims when satellite connections get weak or confusing.

    Knowing nothing else, my hypothesis would be that Apple has balanced the radios and built in features of the AW to get the best battery life possible under a wide set of expected uses, and this is impacting tracking performance in some situations. A way to test all this arm-waving, as suggested by others, is to try different fitness software and to also compare the two devices on different routes. Can you find a route that is away from trees and buildings? Maybe a track somewhere? Also, maybe do the tests with and without the host iphone along for the ride. It could be revealing. I'd expect that the devices would perform similarly in some situations, but not all, that the AW does better when it can tether off the iPhone, and that different running software may give more consistent results, but possibly at the expense of battery life.

    Fun stuff!
     
  15. wittyphrase thread starter macrumors regular

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    Jan 6, 2017
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    New York
    #15
    So there’s definitely stuff worth trying in this thread. I’ve not used it with the phone for a run yet. The routes are all sort of tree lined and definitely building lined, though it’s residential, nothing over three stories. I don’t doubt that could affect it as it could any GPS, but it’s mostly the magnitude of the discrepancy that’s concerning me.

    I have only used the Apple workout app, not Strava or NRC yet. I’ll try Strava tomorrow mornin. Not a huge fan of the Nike app.
     
  16. deeddawg macrumors 604

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    Jun 14, 2010
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    US
    #16
    NRC app isn't for everyone, but I like it. Probably got used to it back when the Apple Workout app didn't allow for gps data export even with RunGap, and Strava app couldn't operate standalone. NRC was kind of the only option.

    Couple suggestions in case you hadn't tried them: with the NRC app be sure to turn on "All Metrics" in the setup screen. While running, turning the crown changes between three screens (which metric is displayed primarily).

    My only real gripe with NRC is that it (presently) has no hard-button means to stop or pause a run. Problematic for races where you can't just stop at the finish and let auto-pause kick in. However, Nike Support informed me by email this would be in the upcoming new version, presumably on or around the release of the AW3 Nike edition. Still would like HR displayed as %HRR but can live without that.
     
  17. cfc macrumors 6502a

    cfc

    Joined:
    May 27, 2011
    #17
    I think the theory about it not getting a GPS lock is the most likely explanation. The GPS on the watch is not as good as that on the phone, but the error should not be as large as you are seeing, so I assume that it has not got a lock before you start.

    I have written a workout app that displays a map whilst you exercise and have tested it extensively with and without the iPhone. The app shows a GPS signal strength meter at all times, so you can wait for a good signal before starting a workout. It also shows a breadcrumb trail that changes colour according to the signal strength, so it gives a very clear indication of how the GPS is performing.

    With the iPhone the GPS signal is generally excellent in most conditions. When using the watch it is usually pretty good, but can struggle when conditions are difficult. In particular I find that it can sometimes take quite a while to get an initial lock when only using the watch, especially if you are moving, so I agree that this is probably the reason for the discrepancies.

    The app is called WorkOutDoors if you are interested. There is a new version out soon that uses the full-screen ability in watchOS 4 to display a much better signal strength meter that even shows the accuracy in metres if you tap it. Apologies for the plug!
     
  18. NickYanakiev macrumors member

    Joined:
    Sep 12, 2016
    #18
    I found that distance recorded by my new AW3 Cellular very closely mirrors what my Garmin devices (Edge 1030/Fenix 5X) record. Tracks look less than stellar- I believe that the apple watch is using "smart", rather than "every second" GPS data recording- as per Garmin's terms for it- to conserve battery life.
     
  19. wittyphrase thread starter macrumors regular

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    New York
    #19
    So I went for this morning’s run and used Strava. I started the workout and paused it immediately then stayed at the end of my driveway to stare at the sky for a while having already stretched inside. Garmin 235 gets its lock almost instantly. For reference on the 235 I use GPS + GLONASS and smart recording not every second. Gave it about 30 seconds before I resumed the activity and started the run.

    By the end of 5 miles AW was over by .12 miles. I’m ok with this, especially because it maintained this discrepancy through the entire run instead of slowly creeping up like it did on Saturday’s long run.

    Also realized I had auto-pause on for Saturday’s run, which I turned off this morning. Auto-pause has caused problems when used on my Garmin as well. I realize these are not controlled experiments, but once this race is over I just want to be able to use the watch for more casual running and feel reasonably comfortable about the metrics I’m seeing, that’s all. In addition to the general distance discrepancy from Saturday, it also had my pace at several minutes ahead of my actual pace, though the heart rate seemed right on.

    All of this was overshadowed by another problem this morning where I had a text from Verizon at 1AM “reminding me” that the watch was using NumberShare, and the watch was not able to connect to cellular for the hour or so I was out of the house until I got home and restarted both the watch and the phone. #earlyadopterproblems?
     
  20. ftaok macrumors 603

    ftaok

    Joined:
    Jan 23, 2002
    Location:
    East Coast
    #20
    OK, I also had this issue using the NRC+ app and the Apple Workout app on the AW. When using my AW's GPS, it overestimated distances by 15%. This was verified using the GPS on my iPhone6 (and previous routes tracked on my iPhone5) and various mapping websites using Google Maps data.

    Anyways, I have apparently solved the problem, but I did two things, so I'm unsure what solved the issue, but perhaps you can do them individually.

    1. There are actually 2 settings with the term "Motion and Calibration". They should both be set to on. One of them is easy to find. The other one is a little bit more hidden.

    A. Settings > Privacy > Motion & Fitness

    B. Settings > Privacy > Location Services > System Services > Motion Calibration & Distance​

    Setting A is easy to find, make sure you turn on Fitness Tracking, Health and any app you want to use.

    Setting B was turned off on mine, but it should be turned on.

    2. Unpair, then re-pair your watch your iPhone. This takes a while, but generally, it seems that an un/re-pair solves a lot of problems.

    I did #2 first, and then did #1. After my first run using NRC+, I believe the problem with the 15% overestimate has been solved. I say that "I believe" because I haven't actually done a run using just my AW. It's difficult to explain, so I'll leave it at that unless someone is interested.
     
  21. zhenya macrumors 603

    zhenya

    Joined:
    Jan 6, 2005
    #21
    If you were using Auto-Pause on the AW that definitely could have the kind of effect you are seeing. I've never used it on any device - Apple or Garmin - where it works satisfactorily if you are picky about the measured distance.
     
  22. runone, Oct 2, 2017
    Last edited: Oct 2, 2017

    runone macrumors newbie

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    Oct 2, 2017
    #22
    I've had an old Garmin 305 in the past, and it was considerably more accurate than my AW3. I've tried several running apps, but don't have enough data yet to see if one is any better than the others. So far I've tested with the default Apple workout app, Runkeeper, Runtastic, ISmoothRun, and Strava. I test by running around a small running track which is about 250m. It is somewhat oval, with very sharp bends (due to the small size of the track).

    Most apps seem to lack a GPS strength signal which is annoying, as I would guess some of the inaccuracy I see is partly due to poor lock at the start of a run. Runkeeper does seem to have signal strength displayed.

    It is impossible to guess what the internal sampling rate is of the apps, because the frequency with which they write out points is not necessarily the same as what they are sampling the GPS data at. The Apple workout app is writing out at 1 point per second. The rest are all using variable write rates, of around 3-6 seconds. I suspect they are using what Garmin would call 'smart recording' where they only write out a point when pace or direction has changed, so saving on the total file size. It is possible apple uses a private API to talk to the GPS that allows them to sample more often than the other apps, and the other apps are only seeing the data they are writing, and the official gps APIs are not giving them raw data but already massaged data, which would be a pity, as it would make it harder to provide their own smoothing algorithms.

    I think the quality of smoothing algorithms has a lot to do with the differences, and so far the apple output seems less smart about this than some of the third party apps, but I need to do some more tests with the the apple app to make sure I'm getting a proper lock before running.

    For now, I'm not really looking at distance, as I think the movement detection used for step counting etc is a confounding factor here, as it can provide distance data also. For now I'm purely looking at how the resulting maps in satellite mode line up with the track I'm running on, which I think is a much better test of pure GPS accuracy than looking at distance, at least in the apple app which is a bit of a black box in terms of where the data is coming from (you can use something like rungap to grab GPX files out of the apple workout app, but I haven't compared the distance of the pure GPS track to what the app reports as the run distance yet).

    EDIT: I've just installed cfc's WorkOutDoors app, so I'll add that to the apps I'm testing. Seeing a record of signal strength over the course of the run sounds like a great way to test.
     
  23. wittyphrase thread starter macrumors regular

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    #23
    This looks interesting. I'll check it out. Out of curiosity, is this what the colored trail from the Apple Workout app means as well? If so then that's pretty telling about that run.
     
  24. cfc macrumors 6502a

    cfc

    Joined:
    May 27, 2011
    #24
    The Apple trail is coloured by speed: green is fast, yellow is medium, red is slow.

    WorkOutDoors allows you to see a similar trail on the watch at any time during a workout (rather than just afterwards).

    You can choose from speed (using the same green, yellow and red), elevation (using pink for uphill, light blue for downhill) or heartrate (using dark red for low and bright red for high). On these screenshots you can see how my heart rate went up and my speed went down as I walked up the bright pink hill in the top left.
    WatchStripTrails.png
    Apologies for going slightly off-topic.
     
  25. klymr macrumors 65816

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    May 16, 2007
    Location:
    Utah
    #25
    The color trail seen in the Workout app indicates your speed. The faster you move, the more green the trail is. The slower you move, the more red.

    EDIT: I somehow missed the post by cfc, my apologies for duplicate information.
     

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