Via points & Shaping Points in loop rides

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Peobody
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Via points & Shaping Points in loop rides

Post by Peobody »

When a loop route is created in Basecamp using waypoints and ad-hoc shaping points that have all been set to not alert, that route, when calculated by the XT, is only one block long (between my start and end point). Setting one of the waypoints to alerting solves the problem. Isn't the XT supposed to follow the route as provided to it by Basecamp? The map is the same in Basecamp and the XT, they are both set for Faster time, the route options set in Basecamp may have different avoidances than the defaults on the XT depending on the route, none of the Device Transfer options are enabled in Basecamp.
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Re: Via points & Shaping Points in loop rides

Post by jfheath »

Thank you for such a clear description of your problem.

Can I check - Is this after you have started riding the route, or before you press Go ?

If it is after pressing Go, then this will happen if:
  • the start and end are the same point,
  • the route crosses over itself,
  • you join the magenta line after the last Shaping point.
This used to happen all of the time with the 660. You could start circular route and join it at any place you wanted, and it would continue navigating from there. Those unable to read maps were up in arms about this because it couldn't cope with fig 8 routes, and when following a set course they claimed that the Zumo often missed out one half if the fig 8 by going the wrong way at the cross-over.

In fact it didn't miss it out. It displayed both routes at the cross over and navigated along one if them. Its up to the rider to take the correct one. If you take the correct route it will continue navigating from there. If you take the wrong one it will also continue to navigate from there. If you realise that you have gone wrong, turn round and go back to the crossover and then take the correct route, it will continue navigating correctly from there.

The XT does exactly the same if you have a route that contains only shaping points.

If your problem happens before you press Go! then this is not the answer, and I have other suggestions - but you said that it happens when the route recalculates ....

Today, I discovered something really important. I found another way that doesn't work.
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Re: Via points & Shaping Points in loop rides

Post by Peobody »

jfheath wrote: 23 May 2022 06:07 Thank you for such a clear description of your problem.

Can I check - Is this after you have started riding the route, or before you press Go ?

If it is after pressing Go, then this will happen if:
  • the start and end are the same point,
  • the route crosses over itself,
  • you join the magenta line after the last Shaping point.
Yes, after I press Go.
The start and end points are about 150 yards apart so that shouldn't be it.
The route crosses over itself.
The start point is my house. I select "Closest Entry Point" on the XT.

Of the three potential cause, the figure 8 route appears to be the culprit. Is insuring there is an alerting waypoint mid-route the only way to overcome this?

I am very curious about this for two reasons.
1. To figure out how to deal with it.
2. I have read how a route created in Basecamp contains many, many hidden points which is what insures route integrity when it is transferred to a GPS, at least until it gets recalculated. The preview of the route on the XT is correct yet the XT doesn't follow it. I assume that those many, many hidden points don't have an direction associated with them so can understand a lack of direction at the point where the route crosses over itself but that doesn't explain how all shaping points in the route get ignored.
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Re: Via points & Shaping Points in loop rides

Post by jfheath »

The 'Ghost Points' in the route are invisible. They are followed in sequence - just like ordinary shaping points and via points - so they don't have a direction as such, but the XT has a list, so it knows which one comes next.

But these do not exist once the route has been recalculated. All the XT has to work with are the Shaping Points (and Via Points) to create a new route. I guess that then has a new set of Ghost Points - otherwise it wouldn't be able remember where the newly calculated route goes.

Closest Entry Point ? That turns out to be quite a dangerous tool if your end point is close to where you are currently positioned. CEP ignores Via Points and Shaping points when it is finding the closest point. It calculates a route to the CEP and then follows the sequence of Via and Shaping Points from there on. I have never tested whether or not it loses the ghost points after choosing Closest Entry - but it should keep the remainder of the route points intact.

You say that the route is correct when it is first transferred, but then all of the shaping poitns are ignored.
You don't say whether the correct route (before pressing Go!) shows all of the shaping points.

That would be useful information for me - I am not clear whether the shaping points are shown on the route before Go! was pressed or if they only disappear after CEP has been selected and Go ! is pressed - so if you could post a couple of screen shots ? I don't have USA maps, but I do have OSM maps of around part of North Carolina, from when I was helping Russ with an issue that he was having. I noticed how bad the mapping was around that area !

Is adding Via Points the only way of fixing it ? No - - you can tell it not to recalculate - but it shouldn't be necessary. There there are a lot of things that could be happening here. I'm trying to tease out the information that I need to work out exactly what is happening.

Things that I am considering.

Shaping points are stripped on transfer (see my previous reply).
CEP has been identified as a point between the last ShapingPoint and the end point.
The route is being treated like a navigable track. (Which seems to happen if you deviate from a route after a point has been skipped)
The route is actually a track
CEP is going completely haywire - which can happen in certain situations (eg if U turns are not enabled, or if the current position is close to the start).

Today, I discovered something really important. I found another way that doesn't work.
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Re: Via points & Shaping Points in loop rides

Post by Peobody »

CEP is the problem. The route is fine when I select the starting waypoint instead of CEP. Thank you!

I though CEP was the best choice in most instances. Early in my XT experience I selected the first starting point (which was my home) and the XT didn't recognize that I was already there and tried to u-turn me to it. I have used CEP ever since Obviously CEP has drawbacks. I have read about setting a starting waypoint away from your physical starting point. Now I understand why.

FWIW, the Map button showed the route with all of the shaping points as blue dots. Only after hitting Go and selecting CEP did the resulting route go directly from starting point to ending point. I am not aware of any recalc (recalc is set to prompt).
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Re: Via points & Shaping Points in loop rides

Post by jfheath »

Thank you for the additional information.

So it is finding a point somewhere between the last shaping point and the end - otherwise the shaping point would still be in the route.

In theory, whatever point it chooses as the CEP (and I have established that it is not tempted to head for Via or Shaping points) - it will calculate a route to that point, and continue with the original route from there. Other circumstances may result in that section of the route recalculating as you ride (eg traffic).

I'll see if I can reproduce this here.

Today, I discovered something really important. I found another way that doesn't work.
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Re: Via points & Shaping Points in loop rides

Post by lkraus »

This kind of result is why I no longer start a route AT my home. I keep a couple of standard waypoints in Basecamp, Home S and Home N, which are the two nearest intersections from my house. One of those begins every route. When I begin riding, I can select that point or CEP and the result will be the same.

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