Help me with GPS routing weirdness

Discussion in 'Mapping & Navigation' started by Jamie Z, Jun 22, 2012.

  1. Jamie Z

    Jamie Z Long timer

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    I've tried to search and it seems I must be the only one suffering this problem. It's done this since as long as I've owned this GPS, on a lot (but not all) different routes. The problem is repeatable. If I load the same route, the same problem occurs. It also appears on my Garmin eTrex Legeng HCx, so it's not just the unit.

    When I create a point-to-point route in Mapsource and then transfer it to my GPSMap 478, there are sometimes errors, and I can't figure out why.

    For example, here is how the route looks in Mapsource:

    [​IMG]

    On the GPS, a couple points are inexplicably missing.

    [​IMG]

    Later in the route, as shown in Mapsource:

    [​IMG]

    But on the GPS, it appears as though the points are out of order.

    [​IMG]

    The GPX is attached. This isn't the only route where I've seen this, just an example.

    Anyone have a clue what's happening or how I can fix it?

    Jamie

    Attached Files:

    #1
  2. dlh62c

    dlh62c Long timer

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    Jamie

    I downloaded your file and imported it into Basecamp. I see in Basecamp exactly what you see in Mapsource. My 62s with an OSM Map of TN doesn't jump around as your screen shot of the display at Gilt Edge. Photobucket is screwed up so I can't post my screen shot. Could the map set on the gps be corrupted in some way?

    daryl
    #2
  3. ramz

    ramz Professional Trail Rider

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    Or perhaps a map set mismatch between BC and the GPS unit....
    #3
  4. V-Tom

    V-Tom Been here awhile

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    What happens when the route is (re)calculated?

    ..Tom
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  5. Disco Stu

    Disco Stu Long timer

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    is the mapset you're using in mapsource the same as you have loaded on your gps? i've seen similar issues when creating a route in one mapset then loading it onto a gps with a different mapset.

    also, check your gps and see if you have any avoidances selected, like toll roads, unpaved roads, seasonal foreclosures, etc. the gps may be trying to avoid a particular road type that's part of your route.
    #5
  6. DRTBYK

    DRTBYK All Things GPS

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    Your GPX data is valid. I have seen this condition in the past on several Garmin GPS's. I believe that you are seeing these anomalies because you are placing your route (via) points at road Intersections. Garmin development has repeatedly recommended against do this - even with Direct Routing. Apparently, placing via points on a map intersection can cause unexpected results similar to the ones you show above. Try placing your via points just after the intersection (which is a bit more informative when points are visually far apart).

    Cheers,
    #6
  7. Jamie Z

    Jamie Z Long timer

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    Sorry Tom, I'm not sure. I prefer to use point-to-point. Actually, I think the route gets truncated since it has over the limit that the 478 will route.

    For the 478, both are using CNNA 2013, but it also happened when both were using CNNA 2010. For the Legend HCx, the mapsets are different, as the Legend only has some old Topo maps on it. Maybe from 2008.

    As for avoidances, since the route does not follow the road, I don't think they ought to matter. As it is, I think the only avoidance I have is tolls.

    I saw mention of this in a few of my searches. Apparently there is a difference between route via points and route shape points. The shape points aren't displayed. Looking at the GPX file though, I can't see any difference between the points, and in fact the points show up in my list of turns.

    I will experiment with moving the points a bit from the intersection to see if that helps. That'd be a real pain in the ass though. I hope I can find a simple way to change one point within a route and leave the rest of the route alone.

    Jamie
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  8. DRTBYK

    DRTBYK All Things GPS

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    "Shaping Points" only apply to Along-road Routing not Direct Routing - but, yes, similar condition. You can easily relocate a Route Point in Mac-BaseCamp by using the Select (Arrow) Tool: double-click on the point you want to relocate and then press the ALT+Select Button on you Mouse/TouchPad and drag the Route Point to your desired location. For Win-BaseCamp: Use the Move Point Tool and just click on the Route Point and drag it to your desired location.

    Cheers,
    #8
  9. Jamie Z

    Jamie Z Long timer

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    I've played around with it a bit, and it appears that moving the points at the intersections just a bit solves the problem, but it introduces a new set of problems.

    First of all, since the problem doesn't appear on my computer screen, I don't know there's a problem. It looks like I have to visually compare the Mapsource route and the route I see on the GPS. I have quite a few routes that I would need to check and it's a tedious process to do so.

    Second, my via points go from being named something like "Birch Rd and Autumn Ave" to "3482 Birch Rd" which isn't near as pretty. I can edit the name manually, of course, but again, that's more work. Ugh.

    The routes I'm trying to create are for the Mississippi River Trail project, so I'd like them to be usable by the general public, or rather, YFFs.

    Jamie
    #9
  10. DRTBYK

    DRTBYK All Things GPS

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    Since you intend these Direct Route's to be used by the general public, I might suggest that you change your approach.

    Create Waypoints at the Intersections you want to have "pretty" names and then create your route from the waypoints. You will need to carefully place your Waypoints to make sure they pickup the "pretty" name. Using the Waypoint approach should avoid the viapoint issue at intersections and still give your users some meaningful information.

    This approach is dependent upon the users GPS accepting both Direct Routes and Waypoints.

    Cheers,
    #10
  11. V-Tom

    V-Tom Been here awhile

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    You might also look at using TYRE http://www.tyretotravel.com/. Build your routes on Google maps and then let TYRE to convert it to a GPX format or to put it directly on you GPS.

    ..Tom
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  12. DRTBYK

    DRTBYK All Things GPS

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    The above condition has nothing to do with what program created the Route. It has to do with where Via points are placed on the GPS units routable maps. One way to avoid the stated problem is to not use Along-road (auto) Routable Maps. Or, in most of the newer Garmin units, configuring the Routing settings to Direct Routing or Off-Road mode will solve this problem.

    Cheers,
    #12
  13. V-Tom

    V-Tom Been here awhile

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    Yes I understand what you are saying. Putting a via in an intersection might, for example, cause the route to miss an exit ramp, go on to the next exit, turn around and come back. That doesn't cause a via point to dissappear as the OP said. I also don't understnaed how a decison on a route's viability can be discussed without having the route being calculated. I'd use that kind of routing flying my ultralight, but on the road what's the point?

    I have played with TYRE since getting it a week or two ago and found it very easy to work with and it makes tweaking routes very easy to do. Since you can see the results very quickly and easily. The OP posted screen-prints of routes that were not calculated. I don't understand how we can figure out what is going on without seeing the route calculated.

    I think the OP may have (at least partially) answered his own question, though: there is a finite limite to how many points can be in a route, and this varies from device to device. Some routes that required being subdivided on my 60Cx don't need to be divided on my Zumo 660. I also found in the opast that routes built on a Zumo 550, when transferred to a computer and then to my 60Cx, would not run properly at all on the 60Cx.

    ..Tom
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  14. DRTBYK

    DRTBYK All Things GPS

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    Jamie is using Direct (Point to Point) Routes - I assume because it is impossible to share Along-road Route's such that all how use them get the same results. On most Garmin GPS's that support Direct Routing, the maximum Viapoint limit is 250.

    If it were me, I'd create 500pt Tracks and Waypoints - which provides sufficient data to navigate. If desired or needed, the user can convert the Tracks to Routes compatible with their device.

    Cheers,
    #14
  15. wbbnm

    wbbnm Long timer

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    +1. I agree with Dan. This is what I do. It is a little more work, but you can get what you want displayed.

    Another advantage (at least for me) is that the waypoints will always be displayed on the screen, even when you are not navigating the route. I always convert my routes to tracks for navigation, but I like seeing an occasional waypoint too.
    #15