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GPS issues/drop-outs

So, I've been using the 935 since the day after it was available in the UK without any issues. That is, until last Sunday.

Headed out for my long run, things going well, when I noticed that the 1k autolap times were a bit off. The first few kms were a steady 5:30(ish), when the watch started to report 6:00, then 6:30 followed by a 4:10. Now this was odd as I did not change my pace at all. Stopped the activity (selected resume later), then back to watch face. Start run, continue activity, wait for GPS and off I go again.
Then my wife sends me a message, saying that according to my livetrack session, I'm not moving. So, I thought that the stop/start broke the livetrack. Stopped and saved the run, restarted the watch (as I could not end the livetrack session), started a new run, then everything seemed OK. (After checking the livetrack at home, it was still showing me in our front garden...)

After downloading the data, it was far from OK. There are massive gaps in the GPS track and I have no idea why. I've tracked over 500km with the watch and had no issues until last Sunday.
I went for a run today, same GPS issues.

Last 'working' run:
https://connect.garmin.com/modern/activity/1690665078
(external HR, livetrack)

Sunday run, part 1:
https://connect.garmin.com/modern/activity/1694156439
(external HR, livetrack)

Sunday run, part 2:
https://connect.garmin.com/modern/activity/1694183388
(external HR, livetrack)

Today's run:
https://connect.garmin.com/modern/activity/1697624270
(external HR)

I have the compass added as a data screen. The compass becomes very sluggish to update during a run and sometimes it doesn't even show the heading. It stays blank.

Anybody noticed similar issues?
Things to try? Master reset?

Cheers,
Zoltan

0 zmarkella over 8 years ago

Interestingly, everything is back to normal:
https://connect.garmin.com/modern/activity/1700588386

Added the GPS Lat/Lon data field, just to see if it goes blank at any point, but no issues. :confused:

0 FabioPascua over 8 years ago

It must have been Mr. Trump, playing Star Wars games with the North Koreans...
😜.

0 zmarkella over 8 years ago

So, after a reset (non-prompted non-vol clear), this is still an issue... :(

https://connect.garmin.com/modern/activity/1704984049

I was waiting at the start line, clear weatger, watch facing the sky...GPS goes green in a couple of seconds, then 5 seconds later it turns orange, then red (circle completely disappears). Then the watch gets a fix in 10 seconds or so and the whole cycle starts again.
Decided to switch to GPS + GLONASS, hoping that would help, but it only helped to burn more battery. Looking in the FIT file, there are massive gaps of no GPS data. Grrrrr!!!!

Any ideas? Another reset? Or try the beta firmware?

0 timgrose over 8 years ago

Wow long run - quite near where I am too...

Which activity profile are you in here? Just the standard Run one? Looks a bit like UltraTrac was on but clearly can't be if you was using GPS + GLONASS.

What does Settings, About say for the GPS version?

0 zmarkella over 8 years ago

Wow long run - quite near where I am too...

Which activity profile are you in here? Just the standard Run one? Looks a bit like UltraTrac was on but clearly can't be if you was using GPS + GLONASS.

What does Settings, About say for the GPS version?

It was a DNF 100-miler... :/

I was using the standard 'Run' profile. Auto lap @ 1km + external HR strap (HR-Tri). 1-second recording. I think all other settings left @ default.

GPS version 4.30

0 kalamarios over 8 years ago

This might be of assistance if you have GPS issues. I put together a Connect IQ app (a data field in this case) which displays the reported GPS signal quality and also writes it to the FIT file so you can see it in a graph in Garmin Connect afterwards. GPS signal quality is reported as a number from 0 to 4. 3 and 4 are usable, 2 or less is a problem. The data is fairly crude, but unfortunately it is the best Garmin gives us.

https://apps.garmin.com/en-US/apps/e3f85a7a-7241-4fd1-b6b3-39eddf26ed43

This is an area where Suunto is much better. The SML files that the Ambit 3 produces (I don't know about the Spartan) record the number of satellites (with corresponding SNR) as well as the DoP (dilution of precision) periodically. So if you get a "bad" track, you can very easily look at the SML files (which are simple XML) and see if the satellite geometry was simply poor during that time.

Since quick-start (cached/predicted ephemerides) devices started appearing, the perceived GPS performance has "degraded" in the sense that we have less and less visibility on the constantly varying satellite conditions.

0 timgrose over 8 years ago

Strange why the GPS fix was so flaky then. Might point to a defective watch.

I discovered yesterday that is a GPS elevation data field so might have worth setting up a screen with that and also pace (or speed) and also "GPS" (bar graph) from the Other Fields menu and "watching" it next time before you start the timer. The GPS elevation should be fairly stable and "in the ballpark" and pace should be zeroed out before starting and you should have full bars on GPS.

0 kalamarios over 8 years ago

I discovered yesterday that is a GPS elevation data field so might have worth setting up a screen with that and also pace (or speed) and also "GPS" (bar graph) from the Other Fields menu and "watching" it next time before you start the timer. The GPS elevation should be fairly stable and "in the ballpark" and pace should be zeroed out before starting and you should have full bars on GPS.

I actually find the "speed" datafield to be a better predictor of GPS lock than the "pace" datafield. Instant pace will eventually drop to zero but somehow speed does not.

0 timgrose over 8 years ago

I suspect pace has a more aggressive smoothing algorithm applied to it...

0 ChevronLugs over 8 years ago

So, after a reset (non-prompted non-vol clear), this is still an issue... :(

https://connect.garmin.com/modern/activity/1704984049

I was waiting at the start line, clear weatger, watch facing the sky...GPS goes green in a couple of seconds, then 5 seconds later it turns orange, then red (circle completely disappears). Then the watch gets a fix in 10 seconds or so and the whole cycle starts again.
Decided to switch to GPS + GLONASS, hoping that would help, but it only helped to burn more battery. Looking in the FIT file, there are massive gaps of no GPS data. Grrrrr!!!!

Any ideas? Another reset? Or try the beta firmware?

Exchange it for a new one. My first F5 (slate/black) did the same thing. Strange thing is, I could kill the EPO.bin on the watch and it'd get a GPS lock in no time at all. I now have the silver/blue F5 and it gets lock, keeps it, and tracks are pretty darned good. Super awesome GPS tracks? No. Super accurate distance? No. Works consistently, and pretty darned good? Absolutely.