Re: Weird Routing Behaviour (2)
Posted: Thu Mar 30, 2023 4:37 pm
Thanks @Peobody . I have plenty of thoughts on this. I chose not to mention it becasue it raises a whole load of realted issues, which would detract from the answer that I was giving. But now you have asked the question that needs answering. So here goes. Take a deep breath. I may be some time.Peobody wrote: ↑Thu Mar 30, 2023 2:00 pm
Well said John! I believe there is a consideration not mentioned, and that is that you can not navigate to a shaping point. This is especially important on group rides if a member or members of the group get separated. You need enough Via Points so as to select one as a meet-up point that is not so far ahead as to break the "group ride". I also think it is important to have some that you can select as a starting point should you have to restart the route on your satnav.
Until recently, I felt that shaping points were the cause of some problems with the XT but the testing results shared on this forum indicate otherwise. I don't believe that a 300 mile route containing all shaping points is wise though. Thoughts?
I know that you know a lot of these things - so I am writing for anyone else that reads the thread - as well as answering your specific questions.
I like shaping points because I can ignore them. Typically when I plan a route I plan it for both me and my pillion. I have got plenty to do, but my pillion is sitting there with nothing but to enjoy the ride. So we may need to stop more regularly. So I put in optional stops. They go in as shaping points and pin point the location of the cafe or whatever. I then put a Via point after the cafe stop - on the road that I want to be on whether I stop at the cafe or not. Maybe two miles further up the road.
Then when it comes to deciding whether or not to stop, I can just ignore the instructions to turn off. Put up with the satnav nagging me for 2 miles and rejoin the route as the plotted route and I both head toward the next via point 2 miles ahead.
It also means that I can restart the route by choosing the next destination, when I accidentally stop it when fiddling with it in the cafe - because as you say, onlt the Via points appear in the list of next destinations when starting a route !
For anyone reading this from fresh. 'I can ignore Shaping Points' - is not what it sounds like. The stanav still has the job of getting you to visit them, and it will do that relentlessly if you are off route. As soon as you rejoin the magenta line though, it will stop nagging and focus on getting you to the next point ahead. As long as you do not miss out any Via Points.
Only the Via points are listed when you start a route for the prompt 'Select Next Destination'. None of the Shaping Points are listed. Because of this, and becasue you cannot guarentee that you will be able to get onto the actual start point of a route, and becasue you usually need to go and get fuel, food, negotiate traffic, road works, I NEVER put my start point at the place that I will start a route. It is always (say) a mile up the road at a location that I will have to pass through. In a large town, it will be way beyond the ring road.
When I choose that Via Point as the next destination, the stanav calculates a route to that point and when I reach it, it continues to navigate from there without me having to do anything.
The issue of how this looks on an XT screen when starting a route is described in the link below. It also shows what happens with the route if you choose each of the Via Point options.
app.php/ZXT-P32
Via points are essential to stop the problem that used to happen with the earlier Zumos like the 660s. If you had a circular route and put in the destination the same as your start the route would finish immediately you started it - because you had reached your destination.
If you had a figure of 8 route, at some point the route crosses itself. You go straight over the crossover point. But if you didn't go straight over - or if straight over involved travlling the same bit of road as the other branch of the figure of 8 - you might get the crossover wrong and end up doing just the bottom circle of the figure of 8.
The 660 would let you do that. In fact if the cross over point is an actual cross roads, and you went straight over (correctly to complete begin the top circle of the figure of 8), the 660 would continue navigating without any problem.
If instead, at the cross roads you turned right to complete the bottom circle of the figure of 8, you are on the route, you are heading in the right direction - the 660 wouldn't bat an eyelid - it would continue navigating as if this was the correct road.
So Garmin introduced a different concept. Without actually advertising the fact, they made route points that alert and route points that don't alert. They don't actually tell you (not that I have seen) that the alerting Via Points are 'must visit' points, or that shaping points can be missed out as I described above. But what Via Points do achieve is route that has some very definite staging posts. It divides a route up into clear sections and you have to complete the sections in the correct order. No more problems with figure of 8s or finishing a route before you have started becasue you are at the final destination. You have to visit the intermediat destinations first - the Via Points.
But you can have fun with this becasue the XT will do exactly the same thing. How ? Plot a route with no Via points. Use only shaping points (except for the start and end). Make it a figure of 8. You can do exactly the same trick that I have described above ! Turn off auto-recalc, and if you wander off the route the satnav goes dumb. It no longer talks to you. Rejoin the route anywhere , it will continue to navigate you ahead as soon as you join the route. It doesn't matter that you have missed a load of shaping points.
Playing around like that is really useful in fully understanding when you need Vias and when you need shaping points. And how many liberties you can take with what it is telling you to do.
The XT also performs a similar trick with tracks that have been turned into trips. There are no Via Points, no shaping points. Just a route. The route itself never alters if you deviate from it. What it does is to spot the closest point on the route to your current position and plots a route to take you there. So suppose you set off on a long thin clockwise oval out-and-back anti-clockwise route, initially heading north. The coming back route is on a road that is just a mile over to the left (west) in a number of places. If you wander off route to the left by more than half a mile, the XT is going to spot the closest point as being on the coming home road, and head for that !
No - my routes will always have a few Via Points. Usually placed just after my stopping places. So maybe 3 as well as the start and end. If I don't know or cannot remember where the cafe is, and I have to detour to get to it, I will put a Via Point just before the place where I have to make a decision. And call it something suitable. The satnav will then speak out to me. "In half a mile arriving at "Use B1234 for no coffee". The route will go to the shaping point at the cafe. If I don't want to stop, I will take the B1234 to reach the route after the coffee stop, held firmly in place by another Via Point.
But having the Via Points means that my data display can show the time and distance to the next Via, which my pillion finds extremely useful. If I put in too many of these Via, they become useless on the display. I need them about an hour or so apart so that I know which point it is. There is nothing more annoying for a pillion who sees that there is 45 mins to the next Via (stopping place), and when we reach it it is int he middle of nowhere and the actual coffee place is 20 minutes further on.
Because the transfer of data to the XT results in a name change of some points, but never with Waypoints, I usually create Waypoints in Basecamp. Give them the name that I want, and use those to be set as Via Points.
The XT allows you to edit a route in the trip planner. You can move points around, add new saved points, add new point tapped on the map.
You can even change the status of a point from Via to Shaping and from Shaping to Via. However, therein lies a problem. If you change a Via Point to a Sahping point, the XT relocates it and gives it a different name. Sometimes this is an insignifcant move. Sometimes it works out a nearby location (it seems to want to place it on its faster route from the preceding point to the next point), and puts the shaping point in a position that forces you to take the faster route. This is annoying because the original via point was probably placed where forced the route away formt he faster road.
This behaviour doesn't happen if you change a shaping point to a Via Point. So if you need points on the route so that you can choose them as the next destination, and you don't have a handy Via Point to choose from, then it is perfectly safe to change a Shaping Point into a Via Point. Not safe to alter a Via Point to a Shaping Point.
My prefeered solution - a route with say 5 Via Point sin total including start and end. Maybe 3 or 4 shaping points are necessary between each Via. The link above gives a good example.