[mkgmap-dev] Questions regarding routing

Fri Jun 21 06:29:33 BST 2013

Hi Felix,

Felix Hartmann-2 wrote
> To improve routing, a much better approach would be to check the 
> finished routing graph for heavy road-class changes on intersections. 
> Garmin doesn't like to route from a road-class=4 onto a 0-1. Only 2 or 3 
> are liked. The max difference should be 2. However that will be 
> difficult to achieve.

I tried to implement such a test, but I fear the result is not very useful.
My idea:
List all routing nodes where exactly two road segments meet AND 
the two segments have a large difference in the road-class AND 
both road segments have further connections on the other end.

With the default style, the produced list is not very long, and 
those nodes that I checked are probable not causing trouble.

Anyway, attached is the patch (prints to stdout), maybe it helps you:
print_road-class-changes_v1.patch
<http://gis.19327.n5.nabble.com/file/n5766294/print_road-class-changes_v1.patch>  

I think what you want is a list of those routing nodes that are probably
avoided although a route through them would be much shorter/faster, 
but I have no idea how to find those in a reasonable time.

Gerd

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