[mkgmap-dev] Thoughts on OSM routing

Tue Feb 17 16:28:02 GMT 2009

Toby Speight escribió:
> 0> In article <20090217140024.4c823ae4 at crow>,
> 0> Mark Burton <URL:mailto:markb at ordern.com> ("Mark") wrote:
>
> Mark> Did it think that the splitter was, itself, a left turn?
>
> No, the instruction was something like "keep left, 200m".  It's just
> that not having had routable maps before (unless you count the basemap),
> I was just slightly surprised (I'd seen the sign for the roundabout, and
> was expecting a roundabout instruction).  I'm over it now.
>   
>From my experience with a nuvi I think when the angle between an exit
and the road you are in is small (don't know the exact figure) message
is "keep left/right" instead of "exit left/right", but it means you must
abandon your road and take the one to your left/right, so in the case
above, I think the splitter is being considered as a left turn.
Otherwise you wouldn't receive any message before the roundabout.
>
>   
>>> One thing I do have a concern about is mixing speed rules into
>>> the lines file - I've patched my style as instructed, but now
>>> all roundabouts are drawn the same, because there's a rule for
>>> roundabouts for speed purposes.
>>>       
>
> Mark> Not sure I understand that. The default rules now look like this:
> Mark>
> Mark> junction=roundabout & highway=trunk [0x0c road_class=3 road_speed=5 resolution 16]
> Mark> junction=roundabout & highway=primary [0x0c road_class=3 road_speed=4 resolution 19]
> Mark> junction=roundabout & highway=secondary [0x0c road_class=2 road_speed=3 resolution 20]
> Mark> junction=roundabout & highway=tertiary [0x0c road_class=1 road_speed=3 resolution 20]
> Mark> junction=roundabout & highway=unclassified [0x0c road_class=1 road_speed=2 resolution 21]
> Mark> junction=roundabout [0x0c road_class=0 road_speed=1 resolution 21]
>
> You're right - my niggle was that they all map to 0x0c, and thus
> appear in different colour to the roads they are part of.  Can I
> just change them to match the highway=* rules?
>
> [/me looks at garmin_feature_list.csv] I guess not - presumably this
> is what the device uses to know it's a roundabout rather than a random
> one-way road that just happens to be circular.  Never mind.
>
>
>   
>>> I think that this probably needs a re-think, because it would be
>>> nice to combine information to give a better resultant speed guess
>>> (including features such as traffic signals, number of lanes, etc -
>>> and for roads in "place=*" as described[1] on the OSM wiki).
>>>
>>> [1] <URL: http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed >
>>>       
>
> Mark> The maxspeed tag should be effective as support for that was
> Mark> recently added by Bernhard.
>
> Trouble is that maxspeed refers to the legal maximum; near here there's
> a 30mph-limit road with about 10 sets of lights in half a mile and the
> effective speed is about 10mph (slightly faster on a bike).  Maybe it's
> time to resurrect a proposal for a more realistic speed tag on ways...
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>
>   

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