1. brucedroid's Avatar
    I got a Samsung Gear S3 recently, and I've taken it out for 2 Runs to test it's GPS accuracy.

    For the runs, I've have:
    Location : on, with gps & wifi,
    I'm using the built in S Health App.
    I also ran with no phone (so just the watch standalone)

    I configured Samsung Health so that Strava is a connected Service (i.e. it will send the running data to Strava when i get home after a run)

    First run:
    * S Health said : 5.1Km in 28:05 (5:30 / km)
    (when i got home it did a data sync, as expected, to Strava which gave me my results)
    * Strava said : 5.2km in 26:30 (5:04 / km)

    Second Run
    * S Health said : 5.05Km in 26:49 (5:18 / km)
    * Strava said : 5km in 25:00 (4:58 / km)

    I understand Strava might decide to "correct" some data, and maybe the distances would be different based on different algorithms of GPS points, but oddly the distances are similar, but the times are different!?

    A few things I've noticed
    * The split time of the first 500m is definitely off when running, almost as if it hasnt got hold of GPS at the start of the run. (The avg km/hr for the first 3-4 minutes in S Health starts at 6 and works its way to 12, when I'm probably running fastest then)
    * The general map does look correct - as in, its tracking my location fairly well
    * Samsung says the 3-4 Km was fastest, Strava says the 0-1. Strava i'd think is correct there.

    I know Strava is not a natively Supported app, but its getting the same data from S Health, so the differences are a bit odd.
    04-20-2017 05:13 AM
  2. brucedroid's Avatar
    I see a few comments here which imply this is not unique:
    https://support.strava.com/hc/en-us/...age=5#comments

    It seems the export to Strava is not working 100% at the moment.
    04-20-2017 02:54 PM
  3. p1eric's Avatar
    I experienced exactly what you are describing back in November '16 when I first got the watch. I think S Health is sending the wrong total time to Strava but I don't have any data to back it up right now because I deleted those "bad" exports in Strava and then manually imported the GPX files. I'll re-enable the Strava connection and then go for a run tomorrow and report back with the results.
    04-21-2017 07:31 AM
  4. brucedroid's Avatar
    Thanks p1eric. I also found if I exported the GPX file and manually imported it into Strava the run recorded fine.
    04-21-2017 08:03 AM
  5. yoggee's Avatar
    Brucedroid, try setting location to only GPS. It's more accurate. Take a short trial run to see the difference between S Health & Strava.
    04-22-2017 06:39 PM
  6. p1eric's Avatar
    Here are the results of my test.

    In S Health my workout duration is 34:01 @ 4.04 miles. S Health has the pace listed as 8:19 per mile although my calculations are 8:25 min/mile. I'm not sure how they came up with that number.

    Samsung Gear S3: Samsung Health and Strava Differ on time-shealth.jpg

    Strava is using Moving Time to calculate pace. So 33:05 @ 4:04 does calculate to 8:11 min/mile. The problem is I have no idea where the 33:05 is coming from. I don't see that value anywhere in the S Health app.

    Samsung Gear S3: Samsung Health and Strava Differ on time-strava.jpg

    My best guess it S Health is calling the Strava API and setting the wrong value for Moving Time. When you do a manual import it uses the min/max GPS coordinate times so it ends up being correct. Either way the pace in Strava seems to be calculated by Strava, not sent in as a value from S Health.

    Interestingly the data exported to Runkeeper is accurate with the pace matching what I calculated.

    Samsung Gear S3: Samsung Health and Strava Differ on time-runkeeper.png
    04-23-2017 09:42 AM
  7. wsrobert's Avatar
    Are you using "Auto-Pause"? I've found that causes issues with moving time/elapsed time values recorded in S-Health/Strava.
    04-24-2017 10:24 AM
  8. p1eric's Avatar
    Are you using "Auto-Pause"? I've found that causes issues with moving time/elapsed time values recorded in S-Health/Strava.
    No I do not use Auto-pause. If you look at the screenshot of S Health there is a Workout duration and Total Duration. I think Total Duration is the time from start to finish and Workout Duration is Total minus pauses. I have a 6 second difference because I manually hit pause as soon as the starting countdown finished in order give the GPS and Heart rate monitor time to lock on. Even though I had only a 6 second pause my moving time in Strava (33:05) is almost a minute less than the Workout Duration in S Health (34:01).
    04-24-2017 10:40 AM
  9. brucedroid's Avatar
    @p1eric interesting - thanks for that. Its around 1-1.5 minutes off for me too. Did you find any particular mile split time was off more than others? I found my 1st Km was always the worst in S Health (particularly if you look at the speed graph), and was wondering if the lack of GPS locks was causing some oddities?

    Thanks @wsrobert - I think you are right though that autopause can mess up the data. One run had it and the S Health graph definitely went odd around there. I've tested it without autopause, and had the same export issue though.

    Thanks @yoggee - I've also tested it with GPS only. My impression is that it is more accurate (once it gets a lock) with GPS only. Although it didn't fix the strava issue though.

    Do either of you used the Strava S Health data connection and have it working?

    I actually posted a separate Question specifically about how to improve accuracy - which I may add your comments onto that thread for anyone else that finds it useful

    http://forums.androidcentral.com/sam...-accuracy.html

    One question I did ask there was weather perhaps S Health is the main issue, and maybe other apps would be better.

    I'll do some more tests over the next week and see how it goes.
    04-24-2017 10:45 AM
  10. funkymagicuk's Avatar
    If you change the Strava run type meta tag (the field after "run") to "race", then Strava uses elapsed time instead of moving time (which is works out itself, making assumptions about pausing due to concurrent GPS points in the file being close together).

    That probably gives you a better comparison.
    04-24-2017 11:43 AM
  11. funkymagicuk's Avatar
    What I have found which was odd, was if I export the GPX from S Health, import that into Strava, which syncs the run back into S Health, then the newly created record in S Health (showing Strava as the source) is more accurate...even though it's from the exact same data.

    This leads me to believe that it's the actual sync that S Health does, rather than the recording of data, that is the issue.
    04-24-2017 11:46 AM
  12. brucedroid's Avatar
    @funkymagicuk - Thanks for the tip on choosing "race" in strava for manual uploads.
    I just did a 1.7km run, manually uploaded the GPX in strava
    Regular uploading Strava said 8:20 "moving time"
    With "Race" it choose the more correct 8:45 elapsed time

    So I guess Strava decided a few data points were too close.

    I'm also getting the feeling that there are some bugs, which hopefully will get fixed.
    04-24-2017 12:32 PM

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