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Trying to solve a weird routing problem.


Jamie Z
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I've got a Garmin GPSMap 478 that I use on my motorcycle. Since I bought the GPS (and I'm on my second one) I've had a weird problem when creating routes on Mapsource. On the computer, my routes show up fine, but when I transfer them to the GPS, they don't come out right. See below.

 

Here, the route in Mapsource:

 

missingpoint2.jpg

 

And on the GPS, two points are inexplicably missing:

 

missingpoint.jpg

 

In that same route, Mapsource shows this:

 

outoforder2.jpg

 

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

 

outoforder.jpg

 

Anyone have an explanation or solution to this problem? I haven't been able to find anything online with repeated Google searches.

 

I'd be happy to share the GPX if anyone wants to have a look.

 

Jamie

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There should be an option within Routing setup to 'Lock on Road'. From your images it appears is Not set for lock on road.

That assumes the OP has a routable map. But I think if he did, the option would be "Follow Road" or one of the new profile related equivalents. "Lock On Road" locks the cursor to the road, even if you are off it.

 

Jamie Z, do you know if your map is routable?

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I don't have any of the computer mapping software you are using, nor a Garmin handheld gps, but for a start you might try unchecking automatic route recalculation on the gps device if that option exists.

As you can see, I'm using a point-to-point route, so there's no recalculation.

 

Jamie

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There should be an option within Routing setup to 'Lock on Road'. From your images it appears is Not set for lock on road.

That assumes the OP has a routable map. But I think if he did, the option would be "Follow Road" or one of the new profile related equivalents. "Lock On Road" locks the cursor to the road, even if you are off it.

 

Jamie Z, do you know if your map is routable?

I'm using CNNA 2013. It's routable, but that shouldn't matter since I'm not navigating via roads. I could I guess, but some of the route is not on roads, so point-to-point is the best option.

 

Does anyone know why clicking on "multiquote" doesn't seem to do anything?

 

Jamie

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When you have a P > P = Track you have a straight line, if you have a route there's always a recalculation, unless its off, or different maps (versions) between computer and Gps.

You say you don't navigate via roads, what do you expect to happen?

It seems to do what you want.

Edited by splashy
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I'd be happy to share the GPX if anyone wants to have a look.

 

Jamie

Perhaps looking at an original gpx file destined for import into the GPS device in a text editor would assist in determining where in the process the route points get scrambled. If the exported gpx route file from the mapping software has all the points in the correct order, and if the GPS device is not set to immediately recalculate upon import, it would seem that a correct point to point route should display on the device.

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I don't have any of the computer mapping software you are using, nor a Garmin handheld gps, but for a start you might try unchecking automatic route recalculation on the gps device if that option exists.

Page 88 of the Garmin 378/478 Manual seems to indicate that recalculation can at least be manually controlled with prompts. Marine mode (off-road)is default.

 

Quote:

"Off-Route Recalculation—allows you to set whether the unit

prompts you when it is recalculating your route (Prompted), or

recalculates automatically. Set whether the unit announces the

recalculation (Automatic - Announced) or recalculates silently

(Automatic - Silent). You can turn the off-route recalculation Off."

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I've sort of discovered the source of the problem. It seems that there is a bug (though Garmin doesn't refer to it as a bug that I've seen) that involves route shaping points. Some GPS units interpret route via points as shape points. Shape points do not show up in the route, even though they are in the GPX file and even show up on the directions page on the GPS.

 

It happens at some intersections when the via point is located directly on the intersection. I haven't seen it firsthand, but some forums I've read claim that Garmin has advised that via points should not be placed directly at an intersection, which is counter-intuitive when creating a route. Garmin's advice (again, I've getting this second hand) is to place the via points close to, but not directly on the intersection.

 

Unfortunately, when I created the routes, I went out of my way to make sure that the via points were located at the intersections, not knowing about the bug. It creates much neater via point names, such as "Maple Rd and Mountain Lane," whereas if you place a via point away from the intersection, the via point has the address as the name, such as "3448 Maple Rd." I'd prefer the intersection name since the routes I'm creating are to be shared with the public.

 

In any case, even though I don't have a solution, I do know what's causing this weird behavior.

 

Jamie

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Unfortunately, when I created the routes, I went out of my way to make sure that the via points were located at the intersections, not knowing about the bug.

Jamie

Thank you for explaining this facet of the routing issue on your Garmin handheld device.

 

I usually place any necessary vias at least a short distance past an intersection in the desired direction on Delorme routes for a different reason. That reason is to minimize the number of vias by providing the software with a hint as to the direction I wish the route to take after an intersection.

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