Zumo XT "cannot calculate route" from basecamp!

[sussamb]

I think having the starting point so far away is your problem. My XT often "can not calculate" when the start point is less than 4 miles away.

Really? That shouldn't be an issue, I often have a start point many miles away

[rbentnail]

I think having the starting point so far away is your problem. My XT often "can not calculate" when the start point is less than 4 miles away.

Really? That shouldn't be an issue, I often have a start point many miles away

Yes, really. Does it all the time. I can go only two directions from my driveway. If I pick a route to the left with the start point about 1.5 miles down the road and then make a right and a quick right again to go "the back way" to avoid traffic, my XT will ALWAYS say "cannot calculate route". Always, it has never failed to do so.

Another scenario- I go 2 miles to to the right to a fuel station and fill up. While there, I pick the same route as above. The XT will route me through the most heavily trafficed areas possible. If I choose to go another direct way, the XT will "cannot calculate" even though the start point is only 2 miles away. It has always does this as well, without exception.

In both cases I will wait until I'm on the route before pulling over, pressing start, and pick my "backup" start point further down the road. Even then it sometimes wants me to go back to the start point behind me. Not always, maybe 25% of the time.

To me this is the biggest fault of the XT - my 595 will constantly recalculate to get me to the start point. The XT routinely will not.

[jfheath]

Russ - Can I ask a favour please ? (@rbentnail - just so that the system alerts you).

What you describe is most odd - but your experience with it seems to show consistent behaviour. I'm often inclined to think that there is a mapping problem in the NCarolina maps - from our past experience. But not this time. I wonder if you would mind carrying out a simple experiment ?

1. Create a simple route in Basecamp. I don't care which roads it takes - it doesn't matter - just one that you suspect will display the same behaviour... Keep it simple. Maybe a route that you have created before. But ....

2. Create the route using only Waypoints - ie using the BC flag tool. So you have to create those first, then build the route using those points.

I'm pretty sure that you will know how to do this, but for anyone else looking in and wanting to try, Quicky Videos 5 and 6 here describe creating waypoints and creating a route using the saved waypoint. (Less than 3 mins each)

3. Try transferring that route to the XT and seeing if it displays the same odd behaviour. I'm hoping that it will.

4. Delete the route from the XT - but your Waypoints will now be saved in 'Saved' locations (Favourites in the UK)

5. Create a route on the XT. New Route -> Select the start point from Saved/Favourites. Select the End Point from Saved / Favourites. The each of the intermediate points. Make sure they are in the same order as your previous route. Save it with a completely different name so that you can recognise it.

6. Now try it. My hope is that this does not display the same behaviour - and if that is so, it will back up a suggestion that I have just made to Garmin tech support.

I'm not suggesting this as a solution. If it does behave itself, then I probably I do have a solution - but it will help me to pinpoint the precise source of the a number of seemingly unrelated problems.

[FrankB]

@jfheath

6. Now try it. My hope is that this does not display the same behaviour - and if that is so, it will back up a suggestion that I have just made to Garmin tech support.

Can't help thinking that it's related to the subclass field. When you first create WayPoints, that later become ViaPoints, the subclass will be set to
<gpxx:Subclass>000000000000FFFFFFFFFFFFFFFFFFFFFFFF</gpxx:Subclass>
Would that be the suggestion you made to Garmin tech support?

[jfheath]

That's the conclusion I came to as well, and need to test it out. But I have already made that observation and suggestion to tech support. Once a long time ago and again yesterday with a lot more supporting 'evidence' that suggests this might be the cause.

First thought was to use MRA GPX V1.1 as that has no route info, but it does use the default subclass of zeros and Fs. But Stu says that he has experienced the Repetitive U Turn phenomenon, and he uses MRA. So I have some tests to complete to pin it down tighter.

But Route points often get their name changed from what they were in Basecamp to what they become in the XT - unless they are first created as Waypoints.

My current favourite suspicion is a misunderstanding in the coding of the subclass pattern in that hexadecimal subclass string of characters - between the Basecamp version and what is understood by the XT. Perhaps as simple as somebody not recognising that the first bit (binary digit) is normally regarded as position 0, not position 1.

I could see how that sort of misunderstanding might impact on various random routing issues that I have observed, assuming that the string contains info such as road type, speed info, routing type. But that is all assumption and mere speculation - but as I said to the person at tech support - I used to teach programming and got pretty good at spotting student errors very quickly, and if I was looking for an error anywhere given the evidence I have presented, that would be the one of the first places that I'd look.

So my next task is to try to pin it down firmly on that subclass string. Or not. Either way it will be the next step forward.

Yesterday I repeated a test which had gone very badly wrong. On the first two occasions, I used a route from Basecamp and when navigating, I skipped a couple of points and then deviated from the plotted route. At point I spotted that it had introduced a via point at the place where I deviated. It didn't show on the map, but it was there in the skip list.

I have proved to my satisfaction that the route does not attempt to get to the next route point when it gets into this RUT scenario. (Repeated U turns). Instead it creates a route to get you back, then when you ignore that, it tags a new bit of route onto what was there before, then again. And again - growing the way back to the point of deviation one short section at a time.

This last time I used the same waypoints from Basecamp without a route, and built up the route using the XT trip planner, using those waypoints from Favourites ( or saved). I deliberately missed the start, and second point, skipped them and later deviated from the plotted route. Skipped another point and then navigated away from the plotted route using the same roads as before. This time the recalculation was immediate, taking me along the way I was intending to go. Even though at the point the recalc was made, it was not as fast.

This time it behaved perfectly, just as my 590 would have done.

It might have learned my behaviour, but I had deleted my history before setting off.

[FrankB]

Thank for the info John. It only convinces me more to always clear the subclass field before sending it to the XT, Good luck with the tech support.

[jfheath]

Thank for the info John. It only convinces me more to always clear the subclass field before sending it to the XT, Good luck with the tech support.

Have you found a better way to do this than simply editing the gpx file before sending it to the gpx folder ?

I ask because it is actually the Basecamp /Xt transfer process when the route point names change. So if I do that and then miss out the transfer I'm eliminating two possibilities at the same time - ie the subclass edit, and the transfer - I might end up pointing the finger at subclass, when the fault might be in the transfer.

I did try to produce a BC route without it adding a subclass. I thought that using a straight line ( direct) profile would do it, But the subclass line was still sent in the Gpx file.

[FrankB]

Oh yes. I certainly do. Will send you a PM, because it could get confusing for other readers.

[rbentnail]

Russ - Can I ask a favour please ? (@rbentnail - just so that the system alerts you).

What you describe is most odd - but your experience with it seems to show consistent behaviour. I'm often inclined to think that there is a mapping problem in the NCarolina maps - from our past experience. But not this time. I wonder if you would mind carrying out a simple experiment ?

1. Create a simple route in Basecamp. I don't care which roads it takes - it doesn't matter - just one that you suspect will display the same behaviour... Keep it simple. Maybe a route that you have created before. But ....

2. Create the route using only Waypoints - ie using the BC flag tool. So you have to create those first, then build the route using those points.

I'm pretty sure that you will know how to do this, but for anyone else looking in and wanting to try, Quicky Videos 5 and 6 here describe creating waypoints and creating a route using the saved waypoint. (Less than 3 mins each)

3. Try transferring that route to the XT and seeing if it displays the same odd behaviour. I'm hoping that it will.

4. Delete the route from the XT - but your Waypoints will now be saved in 'Saved' locations (Favourites in the UK)

5. Create a route on the XT. New Route -> Select the start point from Saved/Favourites. Select the End Point from Saved / Favourites. The each of the intermediate points. Make sure they are in the same order as your previous route. Save it with a completely different name so that you can recognise it.

6. Now try it. My hope is that this does not display the same behaviour - and if that is so, it will back up a suggestion that I have just made to Garmin tech support.

I'm not suggesting this as a solution. If it does behave itself, then I probably I do have a solution - but it will help me to pinpoint the precise source of the a number of seemingly unrelated problems.

Give me a few days, I gotta work overnights.

[jfheath]

Thanks Russ. No rush, and then only if you have the time to spare.