[mkgmap-dev] Bug in --check-roundabouts?

Sun Nov 15 17:53:54 GMT 2009

Hi Carlos,

> One user of my maps told me he was getting wrong direction instructions
> for most of the roundabouts in his city (Cerdanyola del Vallés, North of
> Barcelona). Checking roundabouts in that area I found some of them that
> were badly constructed (wrong direction, auto-crossing, etc.) but after
> fixing them the problem continued to happen. Finally I compiled the same
> data without --check-roundabouts and now they are routed correctly.
> osm data can be downloaded here:
> http://mapas.alternativaslibres.es/63240005.osm.gz
> screenshot with the wrong route:
> http://mapas.alternativaslibres.es/imagenes/roundabouts-wrong.png
> screenshot with the right route:
> http://mapas.alternativaslibres.es/imagenes/roundabouts-right.png
> The only difference between the wrong and the right routes is the
> --check-roundabouts option passed to mkgmap.
> OSM:
> http://www.openstreetmap.org/?lat=41.4882&lon=2.1525&zoom=13&layers=B000FTF

If you don't explicitly specify --drive-on-left or --drive-on-right,
it uses the direction of the first roundabout to determine the driving
side and also the expected roundabout direction. So if the first
roundabout it processed was the wrong direction, it would chose that as
the expected direction and reverse the directions of all of the good
roundabouts!

> P.S. Studying this issue I've seen there's no "junction=roundabout {add
> oneway = yes}" rule in the lines style file. Is it hard coded somewhere
> or should we add this line?

You do not need to add that, it's done for you.

Cheers,

Mark