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5 Plus - GPS Distance coming up as much a 20% short in the woods.

Is anyone else having GPS distance measurement problems with the 5 Plus in the woods? I'm in the northeast US, and running mostly technical trails under tree cover.
I've tried 1sec recording and Smart recording. I've waited as much as 5 minutes after the watch acquires gps to let it get locked in. I've tried GPS only and GPS + Glonass. The watch is regularly measuring close to 20% short on distance, particularly on twisty trails. These are courses I've run dozens of times with my last watch as well as having done plenty of group runs with friends who are using other garmin devices.

The point is, I'm 100% certain that the 5 Plus is under measuring the distance. I'm actually on my second unit, (thanks to Clever Training and they're awesome customer service!) and still having the same problem. I'm kind of shocked to not be seeing others having the same problem here on this forum.

Has anyone else had this experience or heard about other 5Plus users who have? I could really use some help here...

0 anthonytee over 6 years ago

thanks for responding. no, it's off.

0 th3oretiker_ over 6 years ago

I wrote about this a few weeks ago: https://forums.garmin.com/forum/on-t...15#post1378215

According to fellrnr this is not limited to the Fenix 5 Plus, even the old Fenix 3 measures about 20% wrong on trails:
http://fellrnr.com/wiki/GPS_Accuracy-TrailSummary
("Trueness" means "Average distance error", as he explains on his page)

My final solution to this problem was to buy a Stryd.

0 AllanOlesen67 over 6 years ago

I have seen the same. There has been threads about it.

In theory, it should be impossible to come up with a too short GPS distance for a run along a straight line. All the GPS errors along the way (with the two end points as a possible exception) would make the measured distance longer, not shorter. So my guess is that Garmin (or the chipset maker) expects the measured distance to be too long, and because of this they use a correction factor to make it shorter when GPS signal is weak. If that is the case, they are obviously overcorrecting!

But I know the subject has Garmin's attention. They have PM'ed me about it to get more information. And I really should get around to collecting the information they ask for.

0 Former Member over 6 years ago

Eeeeek. I do a lot of hiking on trails averaging between 20-30miles per hike. This would mean a 30 mile hike could show up as a 24 mile hike!!! Is this what I should expect when I get my 5+ or have others reported more accurate readings?

0 AllanOlesen67 over 6 years ago

I was unclear in my previous post: I do not have exactly the same problem as the OP. My distances are mostly ok. My instant pace gets slower under tree cover.

0 Browner40 over 6 years ago

I have not observed this, but I have not been doing as much trail running since I got my F5+. I'll keep an eye on it when I do get out for some more runs on the trail soon. I tend to use a foot pod when trail running also, so that might be allowing it to do some correction. I'll try a long trail run both with and without the footpod in the near future and see what I end up with.

0 AllanOlesen67 over 6 years ago

I tend to use a foot pod when trail running also, so that might be allowing it to do some correction.

The pod does not just give correction to the GPS pace. It either provides the pace, or it doesn't. That depends on how you set up your watch. Same goes for distance.

0 Browner40 over 6 years ago

The watch seems to have different settings now than it did the last time I looked at it. I'm not sure when the last time I actually set up my FP was though, it might have been with my F3HR a couple watches ago. It was my understanding that even if it is set to "indoor" the watch will use pace and distance from the footpod if you lose GPS accuracy during an outdoor run and have a footpod connected. That very well might not be the case though.

0 AllanOlesen67 over 6 years ago

"Lose GPS" or "Loose GPS accuracy"?

The former I will believe. The latter not.

0 Former Member over 6 years ago

If I create a route on Garmin Connect and load it to the watch for my hike or trail run, will the watch still report a shorter distance due to GPS issues?