That's why I run with phone in my pocket. It adds a km per 5 km standalone, and both in Endomondo and Samsung Health.
However, is it the same for LTE models?
I have an inkling that if there is no Internet to get map to match GPS it just uses step count to measure distance. Would be quite easy to test. Walk the same distance with GPS on and then off and compare, but at least few kms for better spread.
I thought I was alone.
Watch (Gear S3 classic) says I ran 18.5km when I ran 15km. I didn't notice it was off till last week's Sunday run. All the while I just thought I was getting faster.
But last week Monday, it recorded my 5km run accurately. I cross check all my runs now with separate timer and Google Maps.
I run WITHOUT my phone. And I always wait for my GPS signal lock before I start.
Just hoping there's a fix.
For both times I ran in an event, I cannot get the gps signal. It just blink. Could it be due to a big crowd or no internet connection ? I have no issues where running alone , the signal locked very fast. I'm using Samsung gear frontier S3.
Any run over 10km is a lot (to me) I admire you! :-)
I've gone through lots of other posts, and what I've learned and done since then relating to GPS and lags are to do either of the following or all. I'm no expert so beware and take these with a grain of salt!
1) press the lower button, tap "Recent apps," then tap "Close all"
2) restart my watch
3) reset my watch
4) Samsung Health app tends to add a little more steps and miles, so if you only use GPS Watch, do not take your phone with you. Or turn the phone off.
5) watch can heat up when you run over 30 minutes or whatever, so take that into account; just say'in.
6) if you've owned your watch longer than a year or two, the battery may have lost the original capacity, (especially avid user with GPS/BT/voice etc) and when it's below a certain level, it may throw tantrums with GPS even if it displays 90%... (my speculation).
* There are some videos and instructions on how to replace the battery yourself. (this is more Nuke option! and make sure you test battery by charging over 90% then depleting under 10% and do this for a few days, and see how many days or hours watch stays on.)
you should be able to find some relating posts on Reddit and else.
keep us updated! Good luck!
I've now since moved to the Gear Watch 46mm and the GPS is solid, better than my Fenix 3, and HRM does really well for my needs. Sold the Fenix 3 with HRM (Sapphire, Titanium band) b/c it was tooooo heavy and GW did everything it did with more functions for my need. I keep Garmin Vivoactive 3 on the side for Golf but the GPS is not as good sometimes so each device has a defect of its own - losing several rounds of play :-(
Here are others' view on the GPS:
Review done by TechRadar: (Samsung Gear S3 vs Apple Watch 2 vs Garmin Forerunner 735XT: Battery and GPS 50k test)