Author Topic: Route - "make a U-turn"?  (Read 2407 times)

Route - "make a U-turn"?
« on: 17 May, 2014, 12:25:20 am »
I've just sent a Route (auto-follow road) to the etrex (Vista HCx) to look at, and notice that in the directions (step by step list with red arrows) there are a couple of "make a U-turn" instructions between two points.  They shouldn't be there as the the route simply goes from one point to the other.  Any ideas why they've cropped up?  The route on map looks fine.

Cycle and recycle.   SS Wilson

Re: Route - "make a U-turn"?
« Reply #1 on: 17 May, 2014, 01:34:46 am »
I've found if I have auto follow route on a map drawn route it can stumble and throw up u turns based on which side of the road the route points actually lie on.
Miles cycled 2014 = 3551.5 (Target 7300 :()
Miles cycled 2013 = 6141.4
Miles cycled 2012 = 4038.1

Re: Route - "make a U-turn"?
« Reply #2 on: 17 May, 2014, 08:05:12 am »
Agreed. When plotting a route you have to be careful where you place your waypoints. Another situation is if you place a waypoint at a crossroads but not get it accurately in the middle of the junction. It will then route you 10 yards down the wrong road then tell you make a u turn  :facepalm:
I am often asked, what does YOAV stand for? It stands for Yoav On A Velo

woollypigs

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    • woollypigs
Re: Route - "make a U-turn"?
« Reply #3 on: 17 May, 2014, 10:03:29 am »
A few years ago I had a GPS telling me to do a u-turn where possible while doing 120km/h on a German motorway with no turn off in sight. Not much of a help for you, sorry.
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Re: Route - "make a U-turn"?
« Reply #4 on: 17 May, 2014, 10:44:21 am »
Thanks all.  I'll be following the track anyway, even if the route directions throw a wobbly.  Will have a bit of a play with the waypoint positioning; could also be the result of a slight mismatch between TT-OSM-British isles mapping on mapsource vs etrex I suppose(?)
Cycle and recycle.   SS Wilson

PaulF

  • "World's Scariest Barman"
  • It's only impossible if you stop to think about it
Re: Route - "make a U-turn"?
« Reply #5 on: 17 May, 2014, 11:23:30 am »
Thanks all.  I'll be following the track anyway, even if the route directions throw a wobbly.  Will have a bit of a play with the waypoint positioning; could also be the result of a slight mismatch between TT-OSM-British isles mapping on mapsource vs etrex I suppose(?)

That was my thought - when I'm planning routes in Basecamp it often won't let me make the obvious, for example, left turn. Instead it sends me further down the road, u-turn and then a right turn down the same road. This is on country roads, not dual carriageways and the turns are legal, at least at the junctions I know.

Feanor

  • It's mostly downhill from here.
Re: Route - "make a U-turn"?
« Reply #6 on: 17 May, 2014, 01:46:05 pm »
I've seen the silly U-turns too.

The usual cause is inaccurately placed route points.

If you plonk via-points on your route in mapsource / basecamp on the junctions, with the zoom level set far out, then you may find that the points are not actually on the junction at all.   Zoom in and look: the point may actually be a few m to the right, on what is supposed to be a LH turn.   The machine will then guide you up to the junction, insist you go R, then do a U-turn in a few m, to continue on your way.

This is why the general advice is to place route points some distance along the road you wish to take, not on the junction.

This issue is exacerbated if you plan the route on an online planner with different maps from your GPS.
You may have placed the routepoint *exactly* on the junction on the web based maps, but that may not correspond to the exact position of the junction on the maps in your GPS unit.   So once again, it tries to route you to that point, and then do a U-turn.

Again, place the routepoints well along the road, not at the junctions, to avoid this.
And also, plan your routes using the same maps you plan to ride with.

As has been mentioned already, on Dual Carriageways, these are treated as 2 separate roads in the mapping software.   So you need to be careful where exactly you set the waypoints.

Re: Route - "make a U-turn"?
« Reply #7 on: 17 May, 2014, 04:26:53 pm »
I've seen the silly U-turns too.

The usual cause is inaccurately placed route points.

If you plonk via-points on your route in mapsource / basecamp on the junctions, with the zoom level set far out, then you may find that the points are not actually on the junction at all.   Zoom in and look: the point may actually be a few m to the right, on what is supposed to be a LH turn.   The machine will then guide you up to the junction, insist you go R, then do a U-turn in a few m, to continue on your way.

This is why the general advice is to place route points some distance along the road you wish to take, not on the junction.

This issue is exacerbated if you plan the route on an online planner with different maps from your GPS.
You may have placed the routepoint *exactly* on the junction on the web based maps, but that may not correspond to the exact position of the junction on the maps in your GPS unit.   So once again, it tries to route you to that point, and then do a U-turn.

Again, place the routepoints well along the road, not at the junctions, to avoid this.
And also, plan your routes using the same maps you plan to ride with.

As has been mentioned already, on Dual Carriageways, these are treated as 2 separate roads in the mapping software.   So you need to be careful where exactly you set the waypoints.

+1