[mkgmap-dev] Dead End Check

Thu Aug 30 15:59:54 BST 2012

On 30.08.2012 16:48, Marko Mäkelä wrote:
> I think that a more severe problem are routing islands, because they
> really break routing. Some mappers seem to think that a
> highway=pedestrian area is enough and may even delete an overlapping
> highway=* way as garbage.
>
> As far as I know, currently mkgmap does not check for routing islands.
> It might be hard to avoid false positives near tile (or map extract)
> borders. If we ignore that, is it computationally expensive to detect
> routing islands? (Run Tarjan's algorithm and complain if there are
> several strongly connected components in the routing graph, perhaps?)
Oh I also don't think they mess up with routing (at least not much). But 
they do visually mess up the map, and take data/space that is not 
needed. If this micromapping takes overhand, then at some point, 50% of 
all footways are rubbish in Austria. Outside of Germany and Austria such 
problems virtually not exist, but it seems here more and more mappers 
turn crazy and make Openstreetmap a cadastral map. A simple check for if 
lenght is under 10m and it's a dead end, then delete it. Plus access=no 
/ access=private and length is up to 50m then delete it, would be enough 
to solve 90% of that cases, without any negative impacts (maybe a couple 
of wrongly tagged streets disappear, however if the 50m and access=no // 
access=private behaviour were in the mkgmap default style, I could well 
believe those tagging errors to be corrected quickly, and wrong new ones 
corrected quickly too).

Routing Islands are another point. I would love to have mkgmap search 
for the nearest routable way at each end of a ferry and 
gondolas/chairlifts which is dead ended and connect it via straight line 
(using 0x08 in my case, as I set that type to be invisible and as a 
"highway link" it would give best routing descriptions).
> Best regards,
>
> 	Marko
> _______________________________________________
>

-- 
keep on biking and discovering new trails

Felix
openmtbmap.org & www.velomap.org