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GPS accuracy, 6X vs 5X vs real GPS device vs Xiami dual frequency

RISBAC
over 5 years ago

https://www.navigation-professionell.de/en/garmin-fenix-6x-gps-accuracy-review/

Really interesting comparison. Looking at the GPX tracks, it's interesting to see that even with more accurate devices like the GPSMAP 64sx & the Xiaomi mobile (with its dual frequency GPS that should give it a precision around 12 inches), the tracks aren't that close to each other. The 5X seems less accurate in most cases. The 6X is doing mostly ok. And the GPX distance seems quite similar. But what was the Garmin Connect distance, that's another story :)

  • 0 over 5 years ago in reply to Otto-Destruct
    Otto-Destruct said:
    When a next-gen, L1+L5 band chip becomes practical for inclusion in smartwatches, I suspect we're going to see huge improvements in GPS tracks. (I believe it's the Broadcom BCM47755 used in smartphones - not sure if could be shoe-horned into a watch)

    I remember all the posts about the bad accuracy on the Fenix3. Some said 'If we only get support for Galileo...', other said 'If they only switch to something else than the MediaTek...'.
    In the end they did both and it didn't make any big changes. In the end we just must accept that the Fenix line is a compromise of good enough GPS with all other hardware and battery capacity.

  • 0 over 5 years ago in reply to RISBAC

    I hear you about the pace deficiencies. I have a couple of residential routes that I run multiple times during a week, and I have high and low pace alerts enabled. Pretty consistently there’s a few parts with moderate/heavy tree cover that will cause my high (slower) pace alert to activate. I’m not physically slowing down, but my 6X’s real-time pace will indicate I am. What’s weird is in Garmin Connect those portions of the run will have a completely consistent pace. Not sure where the correction is occurring, but it’s good that it is. 

    Ideally, the onboard accelerometer would be used in conjunction with with the GPS to do some sanity checking. Like, if GPS is reporting a significant change in pace, but the accelerometer doesn’t indicate that then don’t report the change. That obviously would be additional processing that could have a significant battery hit. It’s all about tradeoffs. 

  • 0 over 5 years ago in reply to TobiasLj
    TobiasLj said:
    I remember all the posts about the bad accuracy on the Fenix3. Some said 'If we only get support for Galileo...', other said 'If they only switch to something else than the MediaTek...'.
    In the end they did both and it didn't make any big changes. In the end we just must accept that the Fenix line is a compromise of good enough GPS with all other hardware and battery capacity.

    I'll be the first person to say "The difference between reality and theory is, in theory, there's no difference between the two."

    However, until now changes have focused on the receivers. Galileo and GLONASS added satellites but were still subject to errors due to buildings and terrain (multipath/reflected signal errors) and ionospheric (timing).

    L5 is a huge upgrade to the transmitted signal: double power, higher bandwidth, better frequency band.

    Combined with L1/L2, L5 makes position fixes less subject to errors (time & multipath) that adding more satellites can't fix.

    All theory until they cram one into a watch (and bring L5 fully online c.2024) but I'm still hopeful L5 is going to be silver bullet that makes watches hyper-accurate.

  • 0 over 5 years ago in reply to Otto-Destruct
    Otto-Destruct said:
    All theory until they cram one into a watch (and bring L5 fully online c.2024) but I'm still hopeful L5 is going to be silver bullet that makes watches hyper-accurate.

    So, the watch need a new GPS chip that can receive L5 frequencies? 

  • 0 over 5 years ago in reply to Simone.01

    Yep. I don't think there is any watch on the market compatible with it. But I'm less optimistic than CJOttawa. Mobiles aren't take showing a terrific improvement yet (but maybe due to the fact that L5 is not yet fully active on the satellite end?), and people testing them seem to say that unfortunately, the limiting factor will still be the size and position of the antenna. So while it should help (especially if it eliminates multi paths), better not expect the 30cm precision that L5 can offer in ideal conditions.

  • 0 over 5 years ago in reply to Otto-Destruct

    Hope to see soon a watch with GPS L1+L5 band and E1+E5 for Galileo and then Garmin Fenix GPS will not be rubbish.

  • 0 over 5 years ago in reply to falconeye75

    Well, it depends, if Garmin is still doing its black magic and "fixing" the distance with an algorithm, it can still be wrong ;)

    And without trying to be pessimistic, I read a few papers about the dual band technology, including some first tests with the first small devices able to use it (for now, smartphones), and it doesn't seem to show a tremendous improvement. The conclusion of one serious comparison was that dual frequency is very interesting and should give an improved accuracy for sure BUT on a small device like a smartphone (and even more on a watch), the size of the antenna and of the device will be the limiting factor. The 1 foot accuracy will be only theoretical for those devices. But if at least it's better than the Sony chip accuracy and a bit better than the good old SirfStar chip, that will be welcome for sure !

  • 0 over 5 years ago in reply to RISBAC

    A full constellation of 24, L5-band satellites isn't expected until at least 2021 and the state of the world right now might push that later. TL;DR: we won't know what L5 can do until it's fully operational.