Odd MRA treatment of last shaping point

[tombarrington]

Agree. But they can cause Via/Shaping point to be 'off the road'. That was how my comment was meant.

Despite how precise I tried to be when creating the route on the iPad I found some of the shaping points "off the road" after looking at that route in BaseCamp. I wonder if the HERE map available with the MRA Gold subscription would be better as it's supposed to be the same map Garmin uses. The good news is a shaping point "off the road" doesn't always add turn-by-turn instructions to accommodate it, in my experience.

[Mzokk]

Agree. But they can cause Via/Shaping point to be 'off the road'. That was how my comment was meant.

Despite how precise I tried to be when creating the route on the iPad I found some of the shaping points "off the road" after looking at that route in BaseCamp. I wonder if the HERE map available with the MRA Gold subscription would be better as it's supposed to be the same map Garmin uses. The good news is a shaping point "off the road" doesn't always add turn-by-turn instructions to accommodate it, in my experience.

Screenshot 2025-02-14 155911.jpg (109.7 KiB) Viewed 814 times

Yes, depending on where you are there can be a discrepancy of 10-15m between supposedly the same position of a road in OSM and Here mapping or for that matter Google MyMaps. The gold version of MRA routeplanner allows you to compare OSM, Here and Tom Tom mapping data. The Black line is Here Mapping, the Blue OSM and the Red Tom Tom. This does not cause problems unless the shaping or via point is near a junction which the GPS will interpret as a requirement for a turn. In this case the route was imported from Mymaps as a KML and as you can see the google position was slightly south of the rest of the road lines

[tombarrington]

This does not cause problems unless the shaping or via point is near a junction which the GPS will interpret as a requirement for a turn.

It only recently dawned on me that this was the case. Thanks for providing hard data regarding the positioning of shaping points on different map sets!

[FrankB]

One more thing to consider. How does the map you use on your route-planner (BC or MRA etc) relate to the map you use on your device (XT)? Any discrepancies between those 2 can cause unwanted side-effects.

[tombarrington]

My BaseCamp and Zumo maps are always synched, so that's a good thing. As a separate issue, I found that the MRA map (OpenStreetMap for the basic subscription) routed me differently in one location because it was erroneously shown to have both a railroad crossing and an extra lift gate barrier. This created a long, unnecessary detour. I learned something about submitting changes/corrections to OSM as a result.

[Mzokk]

Just measured the difference in geolocation between google my maps and here mapping at the location shown in the MRA route planner above. Not insignificant at that location.

Screenshot 2025-02-14 175647.jpg (94.06 KiB) Viewed 775 times

[tombarrington]

It's hard for me to tell. How material is that?

[jfheath]

A couple of things.

A via point has to be visited - or more precisely, it has to be recognised that you are approaching it. So if the satnav say "approaching Freds Diner in quarter of a mile on the left" - or whatever it says, then it considers that you have visited it, even if you turn off before reaching it.

In the case in the image, it will never say that you are approaching, because first it has to tell you to turn off.

So in theory, yes it does matter that the via point is not on the road.

But, point number 2 may come into play. I'm not sure what goes on here, but when the Zumo imports a route and its route points, those point seem to be checked against the Zumo's map - and it shifts them to nearby known locations. Usually this means that they are plotted on the road, but not always. So if that happens then that via point is not an issue.

Shaping points are not an issue - if you miss such a point, you are still on the magenta line after the point, the zumo will not care that it was plotted off road.

But that being said the XT and to a greater extent the XT2 dondifferent things with routes if they have been imported from outside, and in some situations if the satnav has to recalculate, it will remove shaping points and allow you to completely miss via points - removing them from the route as well. But if it does that, with the best intentions, it is no longer following the route that you plotted.

For those reasons I always make sure that Vias are plotted precisely. Google maps and other routing software maps are not to be trusted. Except MRA maps, which uses HERE maps that Garmin uses.

Suffice to say it is important to check that route points are accurately placed on roads, and on the correct side of the road. A little error might be insignificant - but the via in a field look very significant.

I've got a link to that situation where a via point is misplaced and what happens when you cant visit it.

app.php/ZXT-P203


But if you go onto the next page from that link - p204 - it shows what happens with an imported gpx route that the zumo has had to recalculate. Those videos are XT1s. The XT2 is yhe same if Tread is not connected, and more draconian if it is connected

[tombarrington]

I hope I can remember half the stuff you've figured out.

Suffice to say it is important to check that route points are accurately placed on roads, and on the correct side of the road.

This is a mistake I've made more than once and now I check my point locations and turn-by-turn directions to ensure I don't have to double back on my route.