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Why is GPS accuracy on my Garmin so rubbish in the mornings.

(54 posts)
  • Started 9 years ago by richardlmpearson
  • Latest reply from Kenny
  • This topic is not a support question

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12

  1. richardlmpearson
    Member

    My Garmin (500) has been misbehaving recently. It is generally OK on the wayu home a t night, but in the mornings, I turn it on outside on the bike and leave it while I continue to get ready, yet still for the first 20 mins of my ride it is all over the place.Accuracy to 300 ft it said on the display.

    this happens even with a completely clear sky.

    I've tried a reset of data and a full factory reset, but still no improvement.

    Does this time of year have anything to do with it? Are satelites falling from the sky? Are they switched off in the morning to save money?

    Any other suggestions?

    Posted 9 years ago #

  2. condor2378
    Member

    Sunspots?

    Increased sunspot activity.

    Posted 9 years ago #

  3. neddie
    Member

    Don't ride off until it's achieved 'lock', otherwise it will take ages.

    Posted 9 years ago #

  4. neddie
    Member

    GPS signals are extremely weak (below the noise floor actually) and are only recovered by massive amounts of averaging/oversampling.

    They can easily be affected by trees, clouds, the exact orientation of the antenna (normally inside the device), etc.

    Posted 9 years ago #

  5. kaputnik
    Moderator

    The most favourable GPS line of sight is fairly low in the sky. Does your workplace have better low-sky visbility than your home? This would mean it is faster and more accurate to lock in the evening, but slower and less precise at home.

    Maybe a single satellite which your device could previously reliably see at home is either malfunctioning or being maintained or something, and therefore you are now struggling to triangulate and get a lock in the morning.

    My knowledge of the GPS system is entirely theoretical, so all this could be codswallop.

    Posted 9 years ago #

  6. richardlmpearson
    Member

    All very interesting and informative. Thanks guys.

    Posted 9 years ago #

  7. I were right about that saddle
    Member

    Are you genuinely in doubt about where you are in the mornings? I've had that problem, but it wasn't to do with GPS.

    Posted 9 years ago #

  8. Uberuce
    Member

    Aliens.

    Posted 9 years ago #

  9. steveo
    Member

    Nope, not us.

    Posted 9 years ago #

  10. Darkerside
    Member

    I'll admit that the only commuting use I get from the blistering performance of my Edge 810 is as a clock (will I make the train?) and thermometer (ooh, it is chilly...)

    Money well spent.

    Posted 9 years ago #

  11. Kenny
    Member

    Wow. When I saw this thread subject, I instantly thought "hey, I knew I wanted to ask this question, I don't remember starting the thread, but I must have!". Then I started reading the first post and I'm still thinking it was me that wrote it. But then I noticed the version of Garmin wasn't right... mine is an 800. And then I noticed the author...

    If it's any consolation, I have the exact same problem as you. I was considering a factory reset, but won't bother since you've tried it. My Garmin is currently unreliable on my morning commute, but rock solid in the evening, despite riding the exact same route each way. I can generally have a rock solid lock before I leave (Corstorphine), but when I get on to the NEPN at Roseburn, the accuracy is already in three figures (feet), and once heading north towards the Red Bridge, it invariably loses visibility of the satellites completely, sometimes for 30 seconds, sometimes for 5 minutes. I've had it lose connection as much as 3 times during one 14 minute journey on the NEPN.

    This only started about 2 or 3 weeks ago - before that, no problems, ever. It's mainly on the NEPN that the problems of total connection loss happens. It once happened near the zoo, but that was a one-off incident (so far).

    It was extremely frustrating as I thought my Garmin was on the blink; now I know it's not, and that satellites have indeed fallen out of the sky. Or something.

    If I discover a resolution I'll let you know. Alternatively, maybe it'll magically get fixed. But the fact it's crap in the morning and fine in the evening totally puzzles me.

    Posted 9 years ago #

  12. gowgowuk
    Member

    Funny! I too noticed some crazy readings in the past few weeks! I've always thought the accuracy of my Edge 500 wasn't that great, but thought that it could be due to the high buildings, but recently, on some occasion (but far from systematically), it goes completely crazy. Have been using for a year or two on this same route without ever observing this. Here is a particularly bad example (real path in blue, Garmin in red):

    Posted 9 years ago #

  13. Instography
    Member

    Since I only use it to clock up the mileage I have exported GPX files of each of the three routes I routinely cover (apart from the run with my mates on a Friday but they're usually at least 15 minutes late, giving it plenty of time to get a signal) so any days when it's misbehaving, I search and replace the date in the relevant GPX and upload that instead.

    Posted 9 years ago #

  14. Greenroofer
    Member

    @gowgowuk - your trace in red looks very odd. Is there something more than the GPS signal at work? For example, if the GPS had lost track when you turned onto Viewforth from Montpelier, it would have drawn a diagonal line showing the shortest distance between the two points it knew, but instead it's drawn the correct right-angle, but in the wrong place. Similarly, it shows the wiggles at Balbirnie Pl, but just in the wrong place. It's almost like it knows the turns you're making, but not where they are on the ground.

    Having said that, the chaos in Dalry is completely bizarre. The only explanation for me is that Strava is trying its best to fit you onto a map.

    How odd.

    My Edge 200 has been fine, if that's any consolation.

    Posted 9 years ago #

  15. neddie
    Member

    Perhaps the Americans are crippling the GPS during Iraqi daylight hours?

    Posted 9 years ago #

  16. gowgowuk
    Member

    @Greenroofer: yes, the chaos is Dalry is bizarre indeed and to be honest, I saw this only a few times to that extend, and only in the recent few weeks. But what you describe as "It's almost like it knows the turns you're making, but not where they are on the ground" happens more often, and in fact is nothing new. See this other example below. What I cannot understand is that it is not systematic at all....

    Posted 9 years ago #

  17. gowgowuk
    Member

    Also, I should have said the time to locate satellites in the morning seems much longer than before.
    Another thing: I also have the Garmin cadence/speed sensors and I left the wheel measurement to "automatic". I've just noticed that the measurement went down from 2140 to 2054. I'm not saying that is the cause of the problem, but what if something went wrong with the speed sensor (misaligned magnet,...). It would then give conflicting data (distances) between the GPS signal and the sensor? Could this be the problem?

    Posted 9 years ago #

  18. richardlmpearson
    Member

    This morning I ran my phone as a back up (if its not recorded it didn't happen)and funnily enough the GPS was a little bit better behaved.

    Maybe its like a footballer and needs some competition for it to perform at its best. I always run Runtastic live on my phone on commute home (to allow Mrs P to time dinner to perfection). This could explain it.

    Some of my recent inaccuracies (top one is accurate):

    Posted 9 years ago #

  19. chdot
    Admin

    http://m.livescience.com/48658-bats-jam-signals-of-competition.html

    Posted 9 years ago #

  20. acsimpson
    Member

    Just a stab in the dark but could this be to do with interference from bike lights? Perhaps not for the GPS signal itself but for the wheel sensor?

    Posted 9 years ago #

  21. sg37409
    Member

    Satallite coverage.
    http://citycyclingedinburgh.info/bbpress/topic.php?id=12383

    Garmin 500's are not the best receivers. I raised the above thread, but shortly afterwards the coverage must have improved over edinburgh at around that time.

    Posted 9 years ago #

  22. Kenny
    Member

    If Richard is having the same issue as I am, then the problem is not that Garmin devices are not the best receivers, but that they have worked absolutely fine for ages, and in the past two or three weeks, have gone a bit nuts. Indeed, I said as such (about them being ace) at the end of your thread! :)

    My Garmin outperformed any other GPS device that I know of, based on looking at traces of friends on Garmin Connect and Strava. But in the last 3 weeks, in the mornings only, it's been pants.

    Posted 9 years ago #

  23. Uberuce
    Member

    I'd try wearing your GPS as a Dynasty-style shoulder pad or affixing it to your head, to see if acsimpson is on to something.

    Posted 9 years ago #

  24. Kenny
    Member

    I use my lights both morning and evening.

    Posted 9 years ago #

  25. Greenroofer
    Member

    @Kenny - I did my weekly Strava upload today and compared the tracking precision of my Garmin 200 on the towpath with a colleague who cycles the same route using (according to Strava) an Android device. My Garmin was mostly tracking the route OK, but it's clear that it was only reporting intermittent positional fixes and something (Strava) was interpolating the track in-between. His Android device was reporting much more frequent positions, so tracked the towpath much more accurately.

    I do remember reading that the Garmin 200 has quite a coarse recording: something like only recording changes in speed and position, rather than actual speed. I think the more expensive ones record a much more precise trace of activity.

    Not sure that helps or is relevant...

    Posted 9 years ago #

  26. Snowy
    Member

    I'd agree with the posts about GPS accuracy being a bit rubbish in the mornings recently. This sort of thing does happen every so often. I've particularly noticed it on my phone when playing gps-based games in areas where it's normally fine.

    I can only conclude that a couple of the most relevant satellites are out of action for maintenance, or something.

    Posted 9 years ago #

  27. Kenny
    Member

    Not sure that helps or is relevant...

    I don't know if it helps either, but it's certainly food for thought, so thanks!

    The tricky thing about Garmin devices is you can be fooled into thinking they are not recording data very often, due to Garmin Connect being a bit crap. Garmin Connect does not show you all the data / GPS points. I think Strava might be the same. If you use a different tool (I have written my own) then you can see all the data points, and thus determine how often the data is being written / stored.

    The Garmin Edge 200 uses "smart recording", and you can't change it, AFAIK. The 500 and 800 uses smart recording by default, but you can change it to record every 1 second. The issue that we're having, though, is to do with GPS accuracy, not how often it records track points. The Garmin tells you how accurate it is all the time. I have not seen a mobile device app being able to tell you this.

    That all said, I think what I will do on Monday is to record my trip using Endomondo or Strava on my phone, and use the Edge as normal, and compare the two. That said, if my mobile then records it really well, I'm not sure where that leaves us, because it doesn't appear to be that the Garmin is broken, since it is recording data at other times ok?

    I'm heading out for a ride tomorrow morning. Let's see what happens then...

    Ramblings over for the night.

    Posted 9 years ago #

  28. Kenny
    Member

    I'd agree with the posts about GPS accuracy being a bit rubbish in the mornings recently. This sort of thing does happen every so often

    Interesting... the monitoring shall continue :)

    Posted 9 years ago #

  29. Kenny
    Member

    Signal was solid as a rock this morning. I took the same route initially on my ride as I do when commuting in - 10ft accuracy. Unbelievable. It's like something is happening during the weekday mornings, but only for Garmin devices. I can't see any time that the GPS signal, and thus my trace, was ever even slightly off.

    http://www.strava.com/activities/216803079

    Posted 9 years ago #

  30. Kenny
    Member

    Went for another ride this morning. Signal solid as a rock again. Weird. It'll be very interesting to see what happens tomorrow morning...

    Posted 9 years ago #

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