[mkgmap-dev] Turn restriction angle checks

Sun Mar 30 12:28:09 BST 2014

On Sat, Mar 29, 2014 at 08:49:53PM +0200, Marko Mäkelä wrote:
>On Sat, Mar 29, 2014 at 08:05:15AM -0700, GerdP wrote:
>>the via-ways branch is almost done
>
>I just cloned and built it, and already addressed one error message 
>that it emitted (redundant turn restriction, prohibiting turn against 
>oneway direction).
>
>In the same crossing, there was a wrong turn restriction that an 
>automated check might detect too:
>
> \
>---->---- (oneway)
>   \
>
>On a crossing like this, there is a very sharp turn (135 degrees to 
>right from the diagonal road to the horizontal road), and the turn 
>restriction said no_left_turn. I guess it should have said 
>no_right_turn. I changed it to only_straight_on (role=from and 
>role=to being the diagonal road).

Maybe the patch is actually trying to address the above situation. The 
above case was version 1 in  
http://www.openstreetmap.org/relation/2350374/history

I think that the new code is generating noise for a U-shaped oneway 
"handles" on major twoway roads (a parking lane for making a break, only 
accessible from one direction of travelling). Here is an example:

2014/03/29 19:56:21 SEVERE (RoadNetwork): 63240005.osm.pbf: Turn 
restriction http://www.openstreetmap.org/browse/relation/298645 (at 
http://www.openstreetmap.org/?mlat=61.346723&mlon=26.206187&zoom=17) 
check special case from = to arc 2014/03/29 19:56:21 SEVERE (RouteNode): 
63240005.osm.pbf: check: old code would have selected wrong arc from 
road  42859595  instead of road  32485453
2014/03/29 19:56:21 SEVERE (RoadNetwork): 63240005.osm.pbf: Turn 
restriction http://www.openstreetmap.org/browse/relation/298646 (at 
http://www.openstreetmap.org/?mlat=61.346238&mlon=26.204694&zoom=17) 
check special case from = to arc 

These two relations are forbidding a U-turn via this "handle". I agree 
that it is more intuitive to map this with only_straight_on, but at the 
same time I think that this should only be a WARNING, not SEVERE.

I will be replacing this kind of situations with only_straight_on, and I 
think that a WARNING is OK. But, I think that mkgmap should generate the 
same routing graph with only_straight_on and no_*_turn (with different 
role=to ways, of course).

	Marko