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GPS Accuracy

Former Member
Former Member
So it begins.

I will have mine Fenix 5 on Saturday and will start doing comparisons to an Ambit 3 Peak. I don't have an F3 to directly compare to as of now.

Anyone have an F3 and F5 to compare?
  • Former Member
    0 Former Member over 8 years ago
    You absolutely should! There is no better place to prove the likes of Garmin and Suunto that something needs to be done about the accuracy of their devices.

    My flatmate asked me to come along on a run around the whole Millwall Ward, where many a GPS devices have fallen victim- no comment needed..VAHR versus F5X
    http://www.mygpsfiles.com/app/#wfp90M17


    Hope my F5 doesn't do that during the LM in that area, lol!

    Have had two runs on the F5 now, coming from a F3. One just 5k and the other a 35k and have to say that it's much the same as the F3 was; if there is even a slight bit of tree coverage over the road it loses where it is until I have clear sky. Makes it very difficult when you're relying on lap pace as part of a LSR for marathon training. I'm unsure if any device would get this correct though without a clear view of the sky! Both the F3 and F5 have been on 1s and GPS+GLONASS (or whatever it is).

    So I'm not happy or disappointed, I'm quite used to it from the F3. What I did get however was a very good readout on my heart rate while working out and that seemed very responsive :)
  • My flatmate asked me to come along on a run around the whole Millwall Ward, where many a GPS devices have fallen victim


    I think I've found something that will meet your needs in Millwall Ward https://www.sccssurvey.co.uk/leica-viva-gs08-plus.html (10mm accuracy in moving mode!). Might need more than a 26mm wrist strap though ;)
  • Hahahah! I should challenge Leica to prove that producing a good result in the area is possible.
    Who knows, I may get an unexpected package with the necessary equipment in the post in the coming weeks :D:D
  • Hope my F5 doesn't do that during the LM in that area, lol!


    Oh, you'll probably be fine with the Millwall bit, that isn't too challenging. It's Canary Wharf, a little bit later, where things will go really berserk. My watch was over 200m out there. (The Millwall part doesn't go along the bits that are really throwing Nick's GPS out. And anyone thinking 'tsk, said the F3 was useless' might want to note that was a 310xt which told me I'd run 27.1 miles by the end :) ).

    If I run London again, I'll definitely be using this or something like it. Last time, I was lapping manually at each mile marker. I missed a couple (hot day and I was struggling), but even then I had a much clearer idea how I was doing than I would've with autolap.
  • Used this in last half and worked well. My 735 was only off by +-0.1 miles at markers so it didn't really matter, but works as stated.

    https://www.dcrainmaker.com/2016/12/pacing-races-garmin.html
  • Same thing I linked to :) - but good to have another testimonial to it.
  • Former Member
    0 Former Member over 8 years ago
    Oh, you'll probably be fine with the Millwall bit, that isn't too challenging. It's Canary Wharf, a little bit later, where things will go really berserk. My watch was over 200m out there. (The Millwall part doesn't go along the bits that are really throwing Nick's GPS out. And anyone thinking 'tsk, said the F3 was useless' might want to note that was a 310xt which told me I'd run 27.1 miles by the end :) ).

    If I run London again, I'll definitely be using this or something like it. Last time, I was lapping manually at each mile marker. I missed a couple (hot day and I was struggling), but even then I had a much clearer idea how I was doing than I would've with autolap.


    Oh joy. I look forward to getting excited about nearly being there according to my watch only to find I'm a mile short, lol! I use that data field quite a lot in training but never raced with it so not sure I'll feel comfortable doing it for the first time in London. Will give it a go in the next 3 weeks and see if I can master it :)

    Looking back at the track from yesterday overlaid on a map, I really can't fault it so even though it lost me under trees it accurately worked out what had happened once it regained signal... not that that helps you when looking at the pace at the time though!
  • It's really not normal for a modern GPS to lose the fix, they will wander off though as the F5 sometimes does. Do you get a pop-up saying there is no GPS?

    As a side note I can recommend Peter's Race Pacer with lap correction too as it shows the exact time ahead/behind in seconds which I find easier to relate to than an ETA (which it also has).
  • Former Member
    0 Former Member over 8 years ago
    It's really not normal for a modern GPS to lose the fix, they will wander off though as the F5 sometimes does. Do you get a pop-up saying there is no GPS?

    As a side note I can recommend Peter's Race Pacer with lap correction too as it shows the exact time ahead/behind in seconds which I find easier to relate to than an ETA (which it also has).


    I had no notification of lost GPS but I see my lap pace drop by maybe 15 seconds per kilometre while under the trees and then once out of them it will jump back to what it should be (and no, I'm not altering my pace, lol!). Same on F3 and F5 going down that particular road and that stretch is probably only 2mins long.

    I'll have a look at that pacer too, thanks :)
  • Oh I see, well that's "instant pace" to you on GPS but it's particularly bad on the F5 compared to say the FR235. You can get around this problem by using a footpod but I prefer to rely on "lap pace" with 1km autolap (or manual lap every 1k during races).