I bought a Fenix 5x sapphire back in April. I love the look, the fit and feel, and all the functionality. Problem is I'm not sure if it's the most accurate or least. My elevation gain and distance readings are always shorter than what others get when I do a group run. Most of the people I run with use other Garmin gps models as well. In the past month I started using the GPS+ Galileo setting but the results are the same. Should I just assume I'm getting more accurate readings than everyone else or is the accuracy just flawed on the Fenix 5x? This was a pretty expensive watch to not be getting accurate readings. =(
I don't find it bad - just can be disappointing compared to other devices - especially when they are a lot cheaper. My ol' Microsoft Band V2 used to lay down some better tracks. I'd compare with some of my mates routes using older Garmins' and other devices and feel I was getting pretty average results sometimes, where I hoped my price premium would have meant I was setting the standard.
Recently I have been running with GPS+Galileo and smart recording and actually found its been the best its been for a while - the Galileo satellites that show above me were in 'staging' before but now show active, so its finally usable. I do ride with a speed sensor though so my speed and distance is always good. Just noticed the tracks appear more accurate and closely follow the trails I ride.
I'll definitely being researching the GPS capability of the 6 a lot more closely than I did with the 5 before taking the plunge on any more Fenix watches though. That said, I wouldn't swap it for another device - I like the features and the battery life wins every time for me.
It is hard to compare one GPS to another and assume any one of them is accurate, because determining accuracy requires you know the real measure in the first place. IME GPS receivers all measure long to some degree because the fix is always off by a little bit so a straight line of travel will produce a zig zag track. The slower you go the less accurate it will be.
In my experience, the Fenix reads about the same as accurate as my GPSMAP 64 and maybe not quite as accurate as my iPhone. That is it is anywhere from 5% to 10% longer than what I can determine as the measure using the minimal number of points in a GPX file on Basecamp or in QGIS. I assume (but don't really know) this is mostly to do with the better processing power on the phone allowing for more accurate algorithms.
My suggestion is that you find a measured path or series of straight line paths in the type of tree cover you normally travel in and make the measurements yourself to gauge the discrepancy. It may take a half hour or so and multiple runs to capture the meaningful amount of variance. If you normally ride along the typical winding mountain bike trials, precision and accuracy is going to be a relative thing for any GPS but good enough for the purpose.
