After reading through all of this information (2 or 3 times) I now have an understanding of what is going on with my NAV V with custom routes (GPX imported).
Good stuff - glad its helping. It is far from easy to get your head round.
But I am wondering how the Zumo 660/665 handles the "off route" recalculation: Does it also abandon the route (like the 590) and recalculate to the next Via or is it somehow sticking to the original route by recalculating to a ghost point?
The 590 / 660 doesn't abandon the entire route. It plots a new route up to the next Shaping Point or Via Point. Beyond that, the route should be exactly what was sent from Basecamp or Mapsource or what was saved having created it on the Zumo. The Zumo 660 behaves in exactly the same way. If it doesn't, then something is amiss - eg your Zumo map is not the same version as the map in Basecamp or Mapsource - or some of the stings in Basecamp are wronf when transferring to your Zumo.
It doesn't recalculate up to a 'Ghost Point'. There are hundreds of these little fixing points, maybe as close together as a few metres. Once the Zumo 590 / 660 recalculates a section of a route, the ghost points from that original section are lost. A 'section' is from where you are now up to the next Via Point or Shaping Point (or whatever the Zumo 660 calls them.
I have friends that I ride with that have the 660 and they sometimes have issues and I am wondering if this might be where they are getting confused. For example, if there is a detour due to road construction my understanding is that my NAV V will abandon a custom route once you leave it (the route).
As above, only the current section between where you are now and the next Shaping Point or Via point is recalculated if AutoRecalc is turned ON. The rest of the original route beyond the next Via Point or Shaping Point remains intact. But yes, you would now be following a completely different route up to the next Via / Shaping point.
To avoid this, I need to set auto recalculation OFF and somehow navigate on my own back to the route where the NAV will then once again continue with the route as planned.
Now this is where there can be lots of confusion. If Auto-recalc is turned OFF, then the original magenta route remains where it is, without being altered on both the 590 and the 660. You can use the map on the Zumos and head to intersect the magenta route somewhere up ahead. What happens next when you meet the magenta route is different for both the Zumo 590 and the Zumo 660.
The Zumo 660 doesn't care what came before. You have intersected the magenta line and it will start to navigate you towards the next via point or shaping point from where you are now. It doesn't care about any points that you plotted and which you may have missed while you were off route. It is brilliant.
The Zumo 590 will behave in a similar way if you have missed out a load of shaping points while you were off route. It realises that you are back on route and continues to navigate you to the next shaping / via point in its list, from where you are now. It will not nag you to go back to the ones that you have missed.
Example: You are heading East, on a route that has Start, Sh1, Sh2, Sh3, Sh4, Sh5, End. Your detour started sometime after Shaping Point 1 (Sh1) but before Sh2. You rejoin the route after Sh4. So you have missed out Sh2, Sh3 and Sh4. Just like the 660, the 590 doesn't care about missed shaping points. It sees you have rejoined the original route. There are no Via points missed out, and it will continue to navigate you along the original route towards Sh5. This is just what you want.
However, the Zumo 590 has software which redefines the behaviour of Via Points. It insists that you visit them.
So same route, heading east, but this time your route has Via Points: Start, Sh1, Sh2, Via3, Via4, Sh5, End
You leave the route after Sh1 and rejoin after Via4 and before Sh5. You are back on the Magenta line, but the satnav is telling you to do a U turn. It is trying to get you back to the points you have missed. Definitely back to Via3, but I think that it will also be trying to get you back to Sh2 as you have not yet rejoined what IT thinks is the route. It is as if it is treating the section between each Via point separately.
That's OK though. There is a Skip button. Press it once to skip each point you have missed, including the shaping points. Keeping track of this and knowing where they are is a problem though. In this situation you would press it until it started to navigate you eastwards.
Simple solution. Restart the route. If you know that you have already passed Via4, then select that as the next destination on the new route, and press Skip once to stop it trying to take you west to Via4.
On the 590 this makes you think carefully about where you put Via points and where you put shaping points.
Why bother with Via points then - because the 590 will not display shaping point information in the trip data display at the side of the screen (Time to Via, Distance to Via), and crucially, it will not present shaping points as an option in the list off next destinations when you start a route.
If I don't have auto recalc OFF then it will forget my route entirely and route me to the next Via using the navigation settings on the device (fastest, curvy, etc.).
This is always the case. If the SatNav 590 or 660 recalculates a route, it always uses the settings in the device, and may come up with a different route from the one that you planned. However, it will always come up with a route that includes all of the Via Points and Shaping points.
Does the 660 operate in the same fashion? Or, does it somehow route back to the original route by going to the nearest ghost points?
Yes it does - as above. When recalculating, ghost points for the present section are, in effect, lost.
However the
Zumo 590 has other tricks up its sleeve. It has different settings for mode of transport (car, bike, offroad) and each of these can store different settings. So routing preferences for the car can be different for the preferences for the bike.
If using Basecamp, the mode of transport (bike, car, custom) is saved with the route, and when you load the route, it uses the routing preferences in the Zumo 590 for the mode of transport that was set in Basecamp. This is quite complex and covered in detail in Section 4 of the document that is attached to the first post of this article. It was added later if you don't have it in your copy.
It also has things which affect the route, including your riding style and Traffic Trends. The latter is updated with the maps and it stores historic traffic flow for roads. So as it gets close to 4:00pm on a Friday, your precious route might suddenly change to quieter roads. Find Traffic Trends and turn it off.
I've attached a new document. Something I wrote a few years back mainly for myself to record some testing. It has all faded in my memory now, but at the time that I wrote it, it was what I observed and deduced about the behaviour of my 660. Terminology has changed since then, as have functions of the software.
I used 'drag point' to indicate what was a shaping point, and I used 'Mid Point' to indicate what is now a via point.
But now if you drag a point and drop it onto a known favourite or waypoint - it actually becomes a Via Point !
Parting Shot
I have assumed that routes are being prepared on Mapsource or Basecamp and are being transferred to the Zumo. If the maps on the Zumo 590 or 660 are not the same as the maps on the computer, then routes are always recalculated. You lose your original planned route before you have even loaded it in.
The same applies if any of the 3 settings in Basecamp for Device Transfer are ticked. It recalculates.
If the route is created and saved in the Zumo 590 or 660, all is OK.
If the route is produced on 3rd party software such as Google maps, then you may have problems. The original route seems to be OK, but as soon as it recalculates, any shaping point s that you put into the route are ignored by the Garmin software, and your route is calculated to the end point.
