[mkgmap-dev] [PATCH] make gps report correct exit when routing through roundabouts

Wed Feb 11 11:17:59 GMT 2009

If you can tell me the necessary incantations to apply a patch I'll
gladly try this out.

Paul

Mark Burton wrote:
> As discussed yesterday, the gps sometimes tells you to leave the roundabout
> at an earlier exit than it should. I believe that whether this happens or
> not is influenced by the angle at which roads are attached to the roundabout or
> something related to the angles between the roundabout segments.
> 
> For example, a roundabout with 4 points, each point having a road, will probably
> work OK if the roads "point" pretty much at the centre of the roundabout, like
> this:
> 
>   |
> -- at --
>   |
> 
> But if the roads are more like this:
> 
> -- --
>   @
> -- --
> 
> the gps is likely to get the exit count wrong.
> 
> The attached patch "frigs" roundabouts by adding an extra point between each
> pair of adjacent nodes. The extra points are positioned "outside" of
> the line joining the two nodes. The effect is to make roundabouts
> "rounder". Unfortunately, it also makes them ugly as the frigging is
> being done by a dumb computer with little aesthetic capability.
> 
> However, the good news is that it appears to make the routing instructions
> specify the correct exit now. YMMV
> 
> If interested, please try this out and report success/failure. In particular,
> it would be good to know if it makes roundabouts that previously were OK, bad.
> 
> The patch is for the current "nod" branch.
> 
> Cheers,
> 
> Mark
> 
> 
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