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Data or routing algorithm glitches

17 Feb 2015
by pmontra
in forum
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Zoom in at the 8 and 9 pins in

You see that the route takes a detour into the town to the south of the channel 8 and 9 are located on. There is a bicycle road along the channel between 8 and 9. If I drag the route from the town to it, the route follows the channel up to the bridge past the town, then goes back on itself and into the town. I don't know if the bridge is marked as impassable from north to south (S to N is OK) or it's the routing algorithm that can't deal with it.

There is a problem with a roundabout between the pins 15 and 16 and also the bicycle bridge over the road (move 15 and 16 over the bicycle road). Again, it's either the data or the algorithm. My bet is on the data in both cases.

I'm not familiar with OSM and I don't know how to check if the data are right. Could anybody point me to a tutorial explaining how I can inspect the data and fix it if it's wrong? I don't expect it to be easy, but I'm genuinely interested. Thanks.


Thu 19 Feb 2015, 12:10

Just looked and yes, it’s an error in the OSM data. I’ve resisted the urge to fix it so that you can delve into it yourself!

If you go to and click on the various sections of route, then you’ll see that the route to the NW and to the SE are separate ways.

That’s absolutely standard practice in OSM, but the problem in this case is that they’re not actually connected: the cycleway from the SE ends with a white dot (no connections) rather than a grey one (connected). So doesn’t know that it can pass from one section to the next.

The solution is easy (assuming you’re using OSM’s standard iD editor) – just drag the end of the cycleway from the SE to the junction. It’ll light up and join to the existing ones. You can then save and the route will be fixed next time we update the data from OSM.

Wed 25 Feb 2015, 10:50

Thank you. I'll register to OSM and try to fix it following your instructions.

Wed 25 Feb 2015, 11:13


The second problem is with the bridge at I see that its access is marked as No for both bicycles and foot, so maybe it's unfinished. I'll check as soon as I can get there and see.

Thanks again for teaching me.

Fri 27 Feb 2015, 10:00

No problem! Planning to update c.t with the latest data from OSM next week.