Different Routes when Changing Via to Shaping to Via
Posted: Tue Sep 13, 2022 4:43 pm
This was one of the first faults that I reported to Garmin about 2 years ago. The fact that if you use the XT to change a Via Point to a Shaping Point, the shaping point is often located in a different place and is renamed. It doesn't happen if you change a shaping point to a Via point though. The name and the location stay the same.
I've been pondering on this for a while, and this - although annoying - is starting to make a bit of sense. Not much, but a bit. Try locating any shaping point using the Zumo screen and it will jump to the nearest known location - so even if your fat fingers place the point nowhere near to a road, when your finger is removed, the point is neatly placed on a road. That is a good thing. I think. Basecamp tends to snap to the nearest known point too - which is why you must ALWAYS check the position of your route points.
But another concern is something that was mentioned a little while back - that the routing changes depending on whether or not you have a Via Point or a Shaping Point. So I did a few tests this afternoon. A three point route. A start, an end, and a mid point. I created two of these routes in Basecamp - one route with a mid shaping point, one with a mid Via Point. The results were the same.
Here are some selected screen shots of one set of results:
Pic 1 Below. The original route.
This is exactly as the route was transferred from BC and imported into the Zumo. The maps are the same, the vehicle is the same. The route does not get recalculated by the Zumo in these circumstances. This is exactly how it was plotted in Basecamp.
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Pic 2 Below. After a forced recalculation
I changed the vehicle to off road, and then changed it back to motorcycle. This forces the route to be completely recalculated, and for that it uses my riding profile, Faster Time and no avoidances. The route in Pic 2 above now takes the A65 road NW towards Kendal - heading for the M6 motorway. It then leaves the motorway for the A686 to get to the Via Point (at a town called Kirkby Stephen). And then continues on A roads - NW then NE to the finish flag at Alston. It does not revisit the M6 motorway again.
This route is OK - I would expect the XT to head for the motorways - to reach that first Via Point. To get to the second via point it still uses the major roads in this case, the A66, before taking the only road from there to the finish flag at Alston. It's not the way I would tide, but the route is a logical choice.
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Pic 3 Below. After changing the Via Point to a Shaping Point.
The mid point was moved by the XT when I changed it to a shaping point - but in this particular example it made no difference to the outcome of the test. I did the same test with a route straight from Basecamp with the shaping point in exactly the same location as the original via. it produced the same result as shown in Pic3 after recalculation.
The route in this case is identical to the route after the Zumo had recalculated the original. Yay. Result.
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Pic 4 Below. After changing the Shaping Point to a Via Point.
Ah. Not so good. This time the route visits the Via Point (which is in exaclty the same position as the shaping point in Pic 3, and it heads straight back to the M6 motorway. The A685 from the Via Point at Kirkby Stephen west to the M6 at Tebay is a fast 60mph road. The XTs decision to do this is not a bad one. It is just surprising that it is different from the route produced when a shaping point is used.
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Ok - thats the end of the pictures, but not the end of the story. Because after doing these tests, I switched the Via point back to a shaping point and observed the result, and then switched the shaping point to a Via point again. I did this another 4 times. Each time I switched the mid point from a Via point to a shaping point I got the same result as shown in Pic 3. The route did not head back to the motorway. (Yes the shaping point moved south a little bit each time, but it didn't seem to affect the outcome).
Each time I switched the shaping point back to a Via Point, the route produced was identical to that shown in Pic 4.
Personally I prefer the route that is calculated after the shaping point.
But I am now wondering if the weird routing behviour can be controlled by this little bit of information. I don't know, but I am going to try. After every Via Point there is a section of code in the GPX file which repeats the instruction 'Faster Time' (or whatever), but this doesn't appear after a shaping point. So I am wondering what would happen to the weird routing behaviour if after every Via point (there will only be a small number of them), you place a shaping point just up the road - say half a mile ? Could this cut down the total number of shaping points required.
Its a long shot, but I am going to try it. First I need to find a route that produced some weird routing.
I've been pondering on this for a while, and this - although annoying - is starting to make a bit of sense. Not much, but a bit. Try locating any shaping point using the Zumo screen and it will jump to the nearest known location - so even if your fat fingers place the point nowhere near to a road, when your finger is removed, the point is neatly placed on a road. That is a good thing. I think. Basecamp tends to snap to the nearest known point too - which is why you must ALWAYS check the position of your route points.
But another concern is something that was mentioned a little while back - that the routing changes depending on whether or not you have a Via Point or a Shaping Point. So I did a few tests this afternoon. A three point route. A start, an end, and a mid point. I created two of these routes in Basecamp - one route with a mid shaping point, one with a mid Via Point. The results were the same.
Here are some selected screen shots of one set of results:
Pic 1 Below. The original route.
This is exactly as the route was transferred from BC and imported into the Zumo. The maps are the same, the vehicle is the same. The route does not get recalculated by the Zumo in these circumstances. This is exactly how it was plotted in Basecamp.
-----------------------------------------------------------------------------------------------------------------------------
Pic 2 Below. After a forced recalculation
I changed the vehicle to off road, and then changed it back to motorcycle. This forces the route to be completely recalculated, and for that it uses my riding profile, Faster Time and no avoidances. The route in Pic 2 above now takes the A65 road NW towards Kendal - heading for the M6 motorway. It then leaves the motorway for the A686 to get to the Via Point (at a town called Kirkby Stephen). And then continues on A roads - NW then NE to the finish flag at Alston. It does not revisit the M6 motorway again.
This route is OK - I would expect the XT to head for the motorways - to reach that first Via Point. To get to the second via point it still uses the major roads in this case, the A66, before taking the only road from there to the finish flag at Alston. It's not the way I would tide, but the route is a logical choice.
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Pic 3 Below. After changing the Via Point to a Shaping Point.
The mid point was moved by the XT when I changed it to a shaping point - but in this particular example it made no difference to the outcome of the test. I did the same test with a route straight from Basecamp with the shaping point in exactly the same location as the original via. it produced the same result as shown in Pic3 after recalculation.
The route in this case is identical to the route after the Zumo had recalculated the original. Yay. Result.
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Pic 4 Below. After changing the Shaping Point to a Via Point.
Ah. Not so good. This time the route visits the Via Point (which is in exaclty the same position as the shaping point in Pic 3, and it heads straight back to the M6 motorway. The A685 from the Via Point at Kirkby Stephen west to the M6 at Tebay is a fast 60mph road. The XTs decision to do this is not a bad one. It is just surprising that it is different from the route produced when a shaping point is used.
------------------------------------------------------------------------------------------------------------------------------
Ok - thats the end of the pictures, but not the end of the story. Because after doing these tests, I switched the Via point back to a shaping point and observed the result, and then switched the shaping point to a Via point again. I did this another 4 times. Each time I switched the mid point from a Via point to a shaping point I got the same result as shown in Pic 3. The route did not head back to the motorway. (Yes the shaping point moved south a little bit each time, but it didn't seem to affect the outcome).
Each time I switched the shaping point back to a Via Point, the route produced was identical to that shown in Pic 4.
Personally I prefer the route that is calculated after the shaping point.
But I am now wondering if the weird routing behviour can be controlled by this little bit of information. I don't know, but I am going to try. After every Via Point there is a section of code in the GPX file which repeats the instruction 'Faster Time' (or whatever), but this doesn't appear after a shaping point. So I am wondering what would happen to the weird routing behaviour if after every Via point (there will only be a small number of them), you place a shaping point just up the road - say half a mile ? Could this cut down the total number of shaping points required.
Its a long shot, but I am going to try it. First I need to find a route that produced some weird routing.