Cannot Calculate Route

[m185945]

I have a route that transfers from BC to Zumo fine. While in BC I used the duplicate operation to create a second copy then I used the invert route option. Regarding the inverted route, as expected I had to manually doctor it up before attempting an import to the Zumo. For the inverted route I managed to reduce the via points considerably. Via points are 251 for a 218 mile route.

To summarize:
- The original route imports from BC to Zumo fine.
- The duplicated and inverted route, when trying to import, the Zumo reports "cannot calculate route".

I read some other posts about reloading maps, but because these two routes are so similar I do not think this is a map problem, but what do I know?

Does anyone have any suggestions to get the duplicated/inverted route to import?

I thank you in advance.

[Peobody]

The one I know is that the relocation of a single route point can fix a "Cannot calculate route" problem. There is no way to determine which one though. What I would try is to open the route in Basecamp (double click to open the list of route points). Now click each one, zoom in on it and move it just a touch making sure it is precisely on a road or on a valid POI and, if on a road, is in the correct lane. Once done, recalculate it in Basecamp and then send it to the XT and see if it will import.

Via points are 251 for a 218 mile route.

What do you mean by this? I read it to mean that you have a via point every .86 miles on average. I just can't imagine that is the case.

[m185945]

Thank you very much for the suggestions. Those tips are the first thing I did and I did find issues but corrected them before posting to the forum.
Yes, I do have 251 via points for a 218 mile route. That is how I prevent the Zumo from taking me off my desired route.

Thanks again.

[FrankB]

When I read 'an inverted route' and '251 via-points' it could be that one or more are on the wrong lane of a highway. (in the opposite direction) Or maybe on a one-way road, or roundabaout on the wrong side.

Edit: Come to think of it. There cant be 251 via-points. The majority must be shaping-points (DONT alert on arrival)

[m185945]

When I read 'an inverted route' and '251 via-points' it could be that one or more are on the wrong lane of a highway. (in the opposite direction) Or maybe on a one-way road, or roundabaout on the wrong side.

Edit: Come to think of it. There cant be 251 via-points. The majority must be shaping-points (DONT alert on arrival)

Thank you for the idea. I have used inverted routes before so I'm aware of shaping points on the wrong side of a divided highway. I had made all the corrects I could find visually.

I apologize for using the term "via-points" instead of shaping points.

[Peobody]

I can't explain why moving a waypoint will solve the problem when its placement looks ok visually. I have only ever done with with via points though. The only way I could solve the problem one time was to create a new route, manually duplicating the problem route. Visually, the routes looked identical but there was something in the first one that the XT didn't like and I couldn't identify.

[m185945]

I understand. I hope it doesn't come to that, but I understand the potential. One time I had a route with too many points and it gave me the same error message (cannot calculate route). My one-off solution wasn't much better--I used the BC operation "divide."

[lkraus]

There a couple points here that may not affect the "cannot calculate" problem, but I think should still be clarified, even though it is probably all old news to the regulars here.

The XT will split a route with too many via points into separate routes of 30 or less via points. There is also a maximum of 125 shaping points allowed between any two via points. I have no idea what the XT will do if you give it a route with more than that because I've never needed more than a dozen or so between two via points to pin a route in place, even on a section using multiple roads.

When checking point placement, be sure the "Center Map" box is checked after opening the route. Then, as you click each point in the list, the map will automatically pan and zoom to an appropriate level while highlighting the point, making it quick and easy to verify that the point is on the road.

center.jpg (18.45 KiB) Viewed 1217 times

The route summary in Basecamp combines via and shaping points and reports the total as via points, which can cause confusion. This route actually has six via points and 18 shaping points:

points.png (4.23 KiB) Viewed 1217 times

(I have no clue what the 96 "Points" represent)

[danham]

Without seeing the route, this is only a guess, but I have to believe that the large number of shaping points is choking the XT. I have never had to use that many shaping points to force route integrity, and I've done a lot of long-distance riding with various Garmins and now the XT.

I would be tempted to take a hard look at those points and eliminate any that are not absolutely necessary to keep the XT on-route. I realize the original route worked and only the inverted one is choking, but I'd still try cutting that number way down, as that may be easier and more efficient than some of the other approaches to fixing the route.

-dan

[m185945]

Dan,
Thank you very much for your feedback. I really appreciate the help.

If you are willing to look at the route in question then I have attached it, but before you spend too much time on it let me add that I have seen this "cannot calculate route" enough times before. I have seen it so often that I always create a spreadsheet that identifies a ratio between miles and via points. Whenever I receive the "cannot calculate route" error I refer to my spreadsheet and sure enough the route with the most via points are the ones that fail. When that happens I perform the suggestions of the forum to reduce the quantity of via points and that has helped. This time, of my 10 routes, this failed route had the highest via points; however, after I removed several via points it is now the 4th ranked in via points (I eliminated about 100 via points), meaning, three routes with more via points successfully imported from BC to Zumo whereas the 4th ranked route still will not import. Please bear in mind that on BC with the zoom level all the way up and with the highest detail I have looked at every via point for anomalies. Initially I found and corrected all the anomalies, but the problem is still present. One more thing. I mentioned this is an inverted copy of a route that did successfully import. The successful route has 340 via points. The unsuccessful route has been reduced to 251 via points.

You mentioned "without seeing the route..." If you are interested I have attached the gpx.

I thank you in advance for any assistance.

Without seeing the route, this is only a guess, but I have to believe that the large number of shaping points is choking the XT. I have never had to use that many shaping points to force route integrity, and I've done a lot of long-distance riding with various Garmins and now the XT.

I would be tempted to take a hard look at those points and eliminate any that are not absolutely necessary to keep the XT on-route. I realize the original route worked and only the inverted one is choking, but I'd still try cutting that number way down, as that may be easier and more efficient than some of the other approaches to fixing the route.

-dan