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Garmin Nuvi & Openstreetmaps - bad routing

  • 12-03-2016 3:48am
    #1
    Pauley2
    Registered Users Posts: 96 ✭✭


    I have a 5 year old Garmin 265W (with Euro maps). I was about to purchase a garmin update but thought I'd give the "Openstreetmaps" free updates (at navmaps.eu) a try first.

    I updated the firmware in my garmin first, then I downloaded the Openstreetmaps update, copied it to a new 8Gb SD card and popped it into my Garmin.

    I powered up, unchecked the old maps, checked the new one and it seemed to work (looks a little different to the original). Plotting a few local routes looked just fine.

    However when I asked it to route Dublin to Galway it completely ignored ALL the motorways (M4, M6), routing my as if it were doing so according to the old garmin map that didn't have the M6.

    I checked my avoidances they were all off - I also tried it with "unpaved roads" checked but it made no difference. The option for "Fastest route" is on...

    It shouldn't do this.. Am I missing something? Anyone else have such issues?

    Would it be safe to assume that the official Garmin update would be any better and use the (new) motorways?

    I'm puzzled! Tx!


Comments

  • #2
    coylemj
    Registered Users, Registered Users 2 Posts: 25,588 ✭✭✭✭coylemj


    You didn't mention toll roads - is there an option to avoid these and is it checked? There is a toll near Enfield on the M4 and another on the M6 near Ballinasloe.


  • #3
    Pauley2
    Registered Users Posts: 96 ✭✭Pauley2


    There is an option to avoid toll roads but it's not checked (ALL avoidances are unchecked). I also have "Faster Time" enabled under Settings/Navigation

    I also just noticed that it also routed me right into the center of Dublin and out the N4 potentially adding about 30 mins of nightmare Dublin city traffic - rather than cut to the N4 via the M50 - which is about 2 miles from the start point on the north side of Dublin and would be the logical choice. - at least the old Garmin map started me out on the M50...

    This is very odd - I don't know anything about how GPS works. My guess (and that's all it is - a guess) is that the routing software in the unit makes its calculations based on how roads on the available maps are prioritised - and that the prioritisation "labels" are wrong on "OpenStreetMaps" (at least for the Dublin Galway route) so the unit doesn't see the motorway as a good option - just a guess...

    I'd love to know if anyone else has seem similar issues or has had weird stuff like this happening with "openstreetmaps"...


  • #4
    Alun
    Registered Users, Registered Users 2 Posts: 21,496 ✭✭✭✭Alun


    Garmin seems to use the posted maximum speed limit as the criterion for calculating "fastest" routes. This usually works well, but can also go wrong as it will often route you via a "short cut" via an unclassified road which in theory has the same 80km/h speed limit as the R road you're already on, but is in fact just a boreen with grass growing up the middle, saving precisely zero time.

    My guess is the Open Streetmap maps, or at least the Irish ones, have no speed limit data in them at all, hence the useless routes.


  • #5
    Pauley2
    Registered Users Posts: 96 ✭✭Pauley2


    Tx. I since visited the Openstreetmaps forums and there are plenty of posts (and arguments) about how roads are classified - if at all. Net result as far as I can see is that it (Openstreetmaps) is of limited use for drivers and can't be relied on for good routing. Looks like I'll have to pony up for the Garmin update...


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