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Forerunner 645M gps + galileo accuracy

Former Member over 5 years ago

Hi,i just bought a new forerunner 645M and tested it against my older forerunner 235.I ran the usual route from work,and noticed imediately that the 645M was wrong of about 30 meters.At the end of my usual 10km run i got 100m+ difference from the 645M. It's only 1% but it's a quite linear route and looking at the map it seems that the watch was worn by spider man.

I tried gps + galileo since i'm from italy and hoping that galileo was more precise for me,but it doesnt seems like that.

Tomorrow i'll try without galileo and i hope that will be bettere.

I'm adding a screenshot of a segment thats quite wrong.

Also the elevation gain was really off 16 meters (645) against 32 meters (235).Using elevation correction on garmin connect on the 645M run gives 32 meters instead of 16 meters

someone know i'f it's going to be fixed the gps+galileo accuracy?

Thanks

0 MickyWicky over 5 years ago

My experience is that the GPS on the 645 isn't great - for example it consistently underestimates distance (by a good 5%-8%). Using Galileo or Glonass doesn't help much with that, so I ended up getting a cheap footpod.

0 kurtie_bcn over 5 years ago

I've got 645 since release, and GPS is not great. It was better in my old FR230, and it was even better in my previous Ambit 2.

Precisely today I've got the worst track ever (see image)... by a lot... GPS was all over the place. I had to stop the activity, and resume it, and after that GPS seemed to be as usual: good but not great.

I've tried Galileo and Glonass and for me they did nothing for accuracy. GPS in this watch is not great, has never been, and it does not seem to improve. For me this is 645's weakest point.

I will do a factory reset because since last firmware I am also having other problems: it tends to hang after saving an activity (I tried to delete all previous activities, but it's still happening), and battery indicator is starting to behave wonky. Not very happy with my 645 lately.

Best,
Kurt.-

0 Former Member over 5 years ago

I tried two more times and as i thought with gps only is far more accurate.I hope that it will work better in 2020 when the Galileo satellite network will be complete.

0 CoffeeU over 5 years ago

The garmin 235 doesn't have an altimeter, so the default is to use elevation corrections via mapping data because gps elevation is so far off.

I owned the 235 and 645 - I've never run with them together. However, I apparently have better luck with my GPS tracking. With my 235, maybe I'd see a 0.25 km section that looked wonky ever 500 km, and with my 645, I'll see a 0.5-1km section look wonky every 300km. My elevation data also seems reasonable. Because there's a number of (mostly quiet) people who's watches work, I don't think this is something that will be fixed in software, but rather is a hardware issue. I'd suggest to push at Garmin support. Garmin offical channels/support does *not* monitor the forums.

Ultra track on the 645 however is garbage for me. I used it on a hundred that was 3 loops of out and back on mostly straight rail trail, so 53.7 km/loop. First loop was measured 49km, second loop brought me to 106, and last loop had me finish around 168km I seem to recall. Oh, and it thought I set my best km time during the middle of this run! Trying to hit a time goal kind of sucks when you realize that your pace could easily be +- 1:00 min/km while trying to math with Ultra brain. (I did get my goal with 14 min to spare)