Zumo XT "cannot calculate route" from basecamp!

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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.

Suddenly something all makes sense to me! I've noticed several times that if I deviate from my route and then skip a point, and then make my way back to my route later (without recalculating) I have to repeat the SKIP process several times, even though I had no points there in the original route, just so I can quit getting u-turn instructions. One time I was off route for about 16 miles and had to pull over to stop and restart the route when I rejoined it. That's the reason I've never believed you (still don't ) when you always say that the route will restart automatically when rejoined. Typically for me it does not.