5x Plus distance accuracy

I did a little distance check this morning with my 5x Plus. MTB ride with low speeds (4-5 mph tight and twisty). Fenix 5x plus (mounted to handlebars), Garmin FR 305 (mounted to handlebars), and Strava Andriod app on my phone (in pocket). All devices allowed ample time to get solid GPS signal/sync. I split the ride up into 3 separate 'rides'. About a 1 1/2 hour total. This is in a wooded city park w/ good cell service, no buildings, just trees. First 2 'rides' had Fenix in GPS+Galileo. On 3rd 'ride' switched to GSP only.

The 305 and the phone actually were very close in total in all three 'rides' created. They almost exactly aligned. Very impressive. The Fenix, on the other hand, consistently lost close to a 1/10th of a mile every 1 mile. I mean really consistently. It did it in both GPS+Galileo and GPS only. I also noticed a big difference in distance when I first got the watch (about 2 weeks ago) compared to my phone in GPS+Glonass mode, but didn't pay too much attention to it at the time.

What is the deal with this? I don't see a issue with the Fenix tracks (had a couple weird ones w/ Glonass), but this distance thing is unacceptable to me. Could it be that the Fenix is the actual accurate one? I doubt it, but I could be wrong.

***Edit: Need more rides before coming to conclusion. Rode again (3.5 miles) and all devices were pretty close.****

0 joshtee over 6 years ago

On a bicycle the best distance result is going to come with the Garmin when the wheel sensor that has successfully done and auto calibration is used as none of the watch’s work well in tight twisty trees

If I keep it, this is probably what I will try. Are they easy to swap from bike to bike? I would need to use it on about 3.

0 nmyeti over 6 years ago

Honestly you might be better off just buying 3. Swapping them is going to be a pain because you'll need to enter a different calibration for each wheel size change. That said, the only place where a speed sensor makes much difference for me is twisty single track in tree cover. Clear sky and on the road I get awesome GPS tracks and distance from a handlebar mount (better results with my 5x than I've ever gotten while running, the 5x+ is new enough that I've only run with it so far). So you might only need one on the MTB, unless you are lucky enough to have 3x MTBs. I'd love to replace my old Litespeed. If you find that you've got too many bikes to buy speed sensors for, i'll gladly trade :)

FYI this is the speed sensor i use https://buy.garmin.com/en-US/US/p/517136. Easy install. You can enter a calibration from your tire size or you can use GPS while on a straight bike path with a decent view of the sky.

0 joshtee over 6 years ago

nmyeti, Yeah, I am finding the same thing with the accuracy, very good in open areas. I just did a driving track and it was a very tight track. Really good. MTB riding single track w/ heavy tree cover, the Fenix has some trouble, but actually, today, it did pretty good.

Flowy single track w/ heavily wooded. Overcast skies. I rode a segment back and forth about 5 times.

Android phone (in shorts pocket): 11.15 mile
FR305: 10.61 miles
Fenix 5 x Plus: 10.5 miles

I put Phone track and Fenix track into mygpsfile.com (I can not get track off FR305, because w/ latest Express update, it will not sync, anymore). A surprise to me, but the 5x Plus track was very tight and the phone's track was a lot less consistent. I wish I could get to the 305's tracks to compare. To me, the 5 x plus seemed to be very accurate. It lagged in distance, but it may be it's the other devices that are the inaccurate ones. Not sure. I guess a speed sensor would help sort that out.

Nmyeti, I do have too many bikes. I am good at buying them, and bad at selling them. I can, in my head, justify keeping each one. :) And as long as it keeps me riding, I'm good with it.

0 joshtee over 6 years ago

Ok, after many tests and comparisons, I have come to the conclusion that the Fenix 5x plus does have 'cleaner' tracks then the Forerunner 305. The tracks, overall, look much better. Less drift and just overall better. Both devices set to 1 second data recording. As far as distance, I do not know which one is more accurate. In wooded tight single track trails, the Fenix 5 X Plus lags behind and ends up with a more conservative distance. In open area roads (residential neighborhoods), the forerunner lags behind and the 5x plus will have a higher distance recorded. I will buy a speed sensor and check distance with that.

0 joshtee over 6 years ago

After having this watch since July, my final conclusion on distance accuracy for this watch is 'Not Accurate', for single track trail MTB riding. I know all GPS devices will not be totally accurate, but a lot do a pretty good job w/ distance plus or minus 2-5%. My 5x plus is consistently minus 10-15% (or more), on distance when riding my normal trails. To me, this is almost a deal breaker. Very frustrating!

There are solutions (kind of). Buy a speed sensor (I bought one). This is not as simple as it sounds. It must be calculated properly. Letting the watch use speed sensor auto calculating is also not accurate. You must manually measure and then some people even use math formulas after this to dial it in better. For multiple bikes it's easiest to have multiple speed sensors. One thing I like about the watch concept is having a all-in-one GPS simplified solution. Having to bother with speed sensors starts to complicate things and increases cost of a already crazy expensive device. The other solution, I have found, is to ride on the road only. Seems pretty accurate in open areas w/ very few turns. Not a solution for me.

Is it too much to ask that a Premium GPS watch to do GPS right (including distance)?? My tracks actually look good and I have not had the problem w/ crazy GPS abnormalities. The distance has been my main problem/concern and it is very very consistently bad. I have no idea if this is something that can actually be fixed through software or if it's a hardware issue. I'm sure someone here knows more. Some have said it is a over filtering issue. Some have said it is that the Fenix has problems under tree cover.

I like a ton of stuff about this watch, but for the price vs performance, I'm starting to think I should have sent it back when I had the chance. Maybe wait for a better version? But the Fenix series has been around for a while. This Watch should be 'Dialed', on the basics, out of the box. When I add distance issues w/ the pretty much useless sleep stats (loved my old fitbit sleep stats), and a few other things, I'm currently not too happy.

If distance is important to you and your noticing what I am, can you please email the beta team. This seems like the only way to possibly get things done. Seems like the people at Garmin who are working on this stuff or can make a difference do not read this forum. Just posting here is pretty much like posting to any other generic forum.

0 indymtb over 6 years ago

Ok, after many tests and comparisons, I have come to the conclusion that the Fenix 5x plus does have 'cleaner' tracks then the Forerunner 305. The tracks, overall, look much better. Less drift and just overall better. Both devices set to 1 second data recording. As far as distance, I do not know which one is more accurate. In wooded tight single track trails, the Fenix 5 X Plus lags behind and ends up with a more conservative distance. In open area roads (residential neighborhoods), the forerunner lags behind and the 5x plus will have a higher distance recorded. I will buy a speed sensor and check distance with that.

I have contributed on this since the Fenix 3. I had the 3 and have the 3HR and 5X+. The 5X+ does intense filtering for smooth tracks. The distance (on tight MTB single-track trails) is off by between 4 - 12% based on canopy and tight turns. Using Garmin's speed/cadence sensor will get you really accurate results and the GPS tracks that go along with it. You have to 1) measure the wheel - chalk the ground - 2) test it compared to a bike gps or the watch gps on open sky and a straight road of about 2 miles. Let it soak for at least 2 miles before taking off 3) take the tire distance times the percentage over the gps. On mine, my tire distance measured 2.04 miles compared to 2.00 miles which was about 2%. I decreased the tire size by 1.5% to compensate for gps. DO NOT use auto-calibrate.

Combine that with Stryd for running and you will not question the watch distances ever.

0 joshtee over 6 years ago

Even though you may be getting decent results with your speed sensor and applying your formula, I don't think having to buy additional accessories/sensors should be a accepted solution.There should be no reason to do this, unless you need absolute accurate distances. Like I said, I am seeing 10-15% (sometimes more) short distances pretty consistently. Plus or minus 2-5% should not be too much to ask from any GPS device. For MTBing, I do not need perfection, but I do expect (everyone should) to be in the ballpark. This watch should calculate distance, by itself, at least as good as other devices that cost 1/5th of the price. Going on a 15 mile group mtb ride and being 2.5-3 miles short, from everyone else, is ridiculous, annoying.

0 indymtb over 6 years ago

No Doubt. I'm just letting you know what I did because I love everything about the watch but the distance stuff on tight single track was frustrating the heck out of me. So I could wait until they get the GPS reception dialed (which could be this watch or a new model) or spend another 10% - 60 dollars to not worry about it. Not the best option but a solution none the less.

0 etparks over 6 years ago

I paced the Wineglass 1/2 Marathon last weekend using a calibrated STRYD. I definitely did not try to run tangents, ran through a short concrete tunnel, and the final distance was 13.14. Pretty happy with the results and the track looked great.

0 joshtee over 6 years ago

No Doubt. I'm just letting you know what I did because I love everything about the watch but the distance stuff on tight single track was frustrating the heck out of me. So I could wait until they get the GPS reception dialed (which could be this watch or a new model) or spend another 10% - 60 dollars to not worry about it. Not the best option but a solution none the less.

I appreciate your solution. I am just super frustrated that I even have to buy and setup external sensors to outfit each of my bikes to get decent ballpark results.