[mkgmap-dev] Problem with --adjust-turn-headings

Tue Feb 9 06:44:56 GMT 2010

Hi Mark,

found a problem in the osm data. there was a short bridge with the name of the exit instead of the motorway name. the turn instruction was exactly as expected according to your implementation.
I have another interesting one here
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=sacramento&sll=37.0625,-95.677068&sspn=58.294644,106.699219&ie=UTF8&hq=&hnear=Sacramento,+California&ll=38.573956,-121.578934&spn=0.000448,0.000814&t=k&z=21&layer=c&cbll=38.573604,-121.581104&panoid=e4tOr0puxhW-8sDps67wRA&cbp=12,89.03,,0,18.64
or in osm
http://www.openstreetmap.org/?lat=38.57493&lon=-121.5694&zoom=16&layers=B000FTFT
Starting at this position I-80 has 3 lanes, to continue on I-80 a keep right instruction is required. But because of same name and same ref no instruction is given. Now adding a through_route relation is an option. But the straight route is also named I-80 BUS and I think in this case an instruction should be given for both routes because the importance is equal for both routes
Is it possible at all to do this in Garmin format? 

And again there is a navi failing this test. Google navi on Android doesn't announce a keep right instruction and I bet 50% who rely on their navi will miss the right turn.

apollinaris

On 8 Feb 2010, at 13:20 , Mark Burton wrote:

> 
> Hi Apollinaris,
> 
>> Hi Mark,
>> 
>> I think I have an example where this is useful. On a ~200km drive I got one
>> keep left announcement where there was only a normal exit from the motorway.
>> 
>> Before blindly adding this relation  I want to understand how the current
>> algorithm should work. maybe I should fix the osm data first
>> you mention mkgmap looks at ways, ref, names. can you explain how it's done?
> 
> Sure. What it does is at each junction, it tries to determine what is
> the "main road" and what is the "side road". If it can determine that,
> it then adjusts the angle at which the side road leaves the main road
> such that it reduces the likelyhood of getting keep left/right
> instructions when you are staying on the main road and increases the
> likelyhood of getting turn left/right instructions when you want to
> take the side road. 
> 
> To determine which arcs make up the main road, it looks at some
> attributes of the routing arcs that enter and leave that node. If two
> arcs have the same ref, it's considered a strong indication that they
> make up a pair, likewise, matching names are considered good.
> 
> The through_route relation is there to help the situation where it's
> not possible to determine from the names/refs of the roads which is the
> main road.
> 
> Before you change any data, could you please post the OSM URL of the
> exit so that I can look at it and see if I can tell why you got a "keep
> left". I am guessing, but I wouldn't be surprised if the exit ramp was
> tagged as a road (motorway, trunk, etc.) and not as a ramp.
> 
>> 
>> btw it's much better than my old tomtom which announces keep left on too
>> many exits.
> 
> Good!
> 
> Cheers,
> 
> Mark
> 
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