Calculation changes Route

[DustyS]

Thanks for all the info.
Any thoughts on how the "Detour" function works? Similar or much different?
Thanks.
Dusty

[jfheath]

Welcome to the forums.

No. I haven't got a clue. It used to do something like leave the route and rejoin afterwards on my 590, but I didn't like the detour that it chose, so I never used it again. I tried it on the XT two days ago when I was out and about. Asked it to detour 5 miles (I knew that there was an easy route it could take). It didn't do anything, and just kept me ont he route.

Probably operator error. Certainly not conclusive, except that I still do not know. Its low priority for me since I didn't like it on the 590 when I could get it to detour.

[Fxwheels]

Detour was and I guess is a problem in all Garmins. I remember how Montana was riding me in circles in Girona for 20 minutes until I stopped following it, because the street ahead was closed.
On a different occasions with Zumo 396 and XT it behaved erratically insisting on u-turns and taking me back where I came from even if I did 2 and 5 miles or just plain detour, until I started to follow the map and got around the closed off section by myself. Detour logic is still an unknown logic and I'm getting shivers when I see a closed section ahead (without a detour arrow). It doesn't happens too often and I'm forgetting or don't have the time experimenting with it.
A quick solution is to follow the screen map until you reunite with the route at some further point or until you see that Zumo did recalculate it right (you still don't know where the road opens up for re-entry, but you're taking a guess).
When I was younger and on a light bike, I could just continue riding and most of the time there was a little tiny section to fit a bike trough...

[casbar]

I had a route that I plotted using MRA and transferred using gpx 1.2. I was in France, deviated from my route in a village and the XT routed me around the village and back onto my original route a mile past the village. It didn't try and take me back to where I went wrong.

[Rofor]

@casbar - IMHO the Zumo XT tries to recalculate the route to the next way- or shaping-point in the pre-planned route and than continues on it. If he tries to takes you back, i think the next way- or shaping-point behind you was nearer than the next point forward....

@jfheath - what we found in the german Naviboard forum i think, it's a fact, that the Zumo XT does a recalculation of a pre-planned route only to the next Way- or Shaping-Point and than continues. The 'old' 59x-series has recalculated to the next 'real' Waypoint - if there wasn't any in your pre-planned route, the recalculation was until to the end of the route, as this normally is in any circumstances a 'real' Waypoint.

This was the biggest problem with route-recalculation and the reason, why after a recalculation has been happened, the route most of the time was completely different to what the users want to drive! The Zumo XT is the first unit, to take care of all points the users has set in a route when doing a recalculation and so it is the first time nearly safe to have turned on recalculation on a unit of the Zumo series...

[Rofor]

@jfheath - For me, the greatest problem of recalculation now is the fact, that in connection with the traffic announcements from Garmin Drive there is some automatic recalculation of the route, which cannot be interrupted, no matter what are your settings on the Zumo XT!

If Garmin Drive sends a traffic announcement to the Zumo XT, that a road on your pre-planned route has a full closure, the Zumo XT will do a recalculation - this recalculation is only(!) announced with a voice message ('Road closure ahead, will use alternative route') and with no visual notice, just like a suggested re-routing because of a traffic jam or a building site, where you can choose to take it or not!

Recalculation Off, or Recalculation after Asking and also the setting in 'Traffic/Optimize Route' doesn't have any impact on the automatic recalculation of the route - you can't abort it!

This is a real bad thing - at all if the traffic announcement is completely false and this happened two times to me!

In June 2020 we were for ten days in southern tyrol, just one day after the border from Austria to Italy has been opened again after the first COVID-19 lockdown. After ten days in southern tyrol on the way back to Austria the Zumo XT suddenly showed 850km(!!!) instead of the planned 350km to the arrival of our overnight stop in Kärnten (Austria). This was about 250km from the Austrian border.

Not aware of this bug/feature(?), i stopped and tried to restart the pre-planned route - this worked for a minute or so and than it does the same recalculation again without any visual notice. I zoomed out the route (sadly not wide enough) to look for a possibly closed mountain street, but can't see anything!? A quick view on the newly calculated route shows me the problem - the Zumo tried to route me from Italy through Slovenia to Hungary, from there to Austria and in Austria back to Kärnten! As i have known the planned route a little, we continue to drive until we came near to the Austrian border.

There i could see the problem - i really don't know why, but there was a traffic announcement, that the border between Italy and Austria was closed (it was already open since twelve days!) and also the border from Slovenia to Austria also!

Last year in june the second time - after a heavy rain a street was partially closed (this was 30km from our hotel and there was a local detour) - Traffic system sends again a 'full road closure' to the Zumo XT and again a automatic, non interruptible recalculation of the route, which would take me for a 120km ride to our hotel!

This time it was easy - stopped the routing, turned off the using of traffic announces on the Zumo, restarted the Zumo and started the pre-planned route again!

I told Garmin every year of this problem and at first, the guy at the support confirmed me, that this shouldn't be so (the automatic, non interruptible recalculation) but nothing happens since the last two years - this bug/feature is already there!
This year i contacted the support again and they told me, that this is passed to the engineers, but they couldn't tell, when or if this will be corrected, because it is hard to understand this problem!?

It's quite easy - look at a local traffic announcement system for a fully(!) closed road, check if this road is also marked as fully closed in the traffic announcements of Garmin Drive and than plan a route in Basecamp, which uses the road. Put the route on the Zumo XT and let it drive a simulation - voila! No chance to stop a recalculation, if the road is marked as 'fully closed'! You don't have to be a software engineer to check this...

For me, it's a absolute no-go to have a non-interruptible recalculation of a pre-planned route, there is always the opportunity, that the traffic message is outdated, not right or completely false - also a closure for a car must not be a closure for all other vehicles, especially for motorbikes! The user MUST HAVE the last word, if he would like a recalculation or not!

[Peobody]

@casbar Do you know what firmware were you were running during your France trip? My sense is that some of the recalc behaviour we are seeing is new. We just don't know if it is associated with a firmware update.

@Rofor I agree about the traffic alerts although I haven't experienced an auto-recalc because of one. I don't trust traffic alerts. Too many false alerts and a several reroutes that that took waaay longer than the announced delay time. The last one caused me to spend 45 minutes in stop-and-go traffic in 90 degree heat to get around what was announced as a 9 minute delay.

[rbentnail]

@rofor Definite problem here as well with the traffic closures. To get past the XT doing stupid things like this I stop the route, disable the Drive app on my phone, then restart the route. No app means no traffic updates or alerts. It's also situations like these that have me interested in learning about using a duplicate track of a route. I have no idea what I'm doing yet but in situations like these I can see it being very useful.

[Fxwheels]

As for the traffic alerts, I've experienced it several times. It sends a message to the screen (and announcing too, but can't remember well) that heavier than normal traffic is ahead and there is an alternatives or in some cases I'm still on a fastest route. I don't normally deviate from the route even onto faster alternatives. Being on a bike it is always possible to beat the traffic. On my latest ride the nav showed 45 minutes to the destination. In few minutes it changed to 1h 30min. There was a problem and police closed off the main road so the traffic was rerouted to where I had the planned route going. They were moving at about 5 miles/hour, but on a motorcycle we took the shoulder and GPS recalculated the time to almost what was initially shown. The point is that traffic is not relevant, but a road closure is, (although sometimes we could beat that too ).