[mkgmap-dev] Turn restrictions with role=via ways

Sun Mar 23 17:16:27 GMT 2014

Hi Marko,

I've created a new branch via_ways to support this.
It is nearly done, but I have to find solutions for
some edge cases like via ways that cross tile boundaries.
Also some routines like RoadMerger are not
yet fully tested.

The current version prints a few error messages for these
edge cases.

Gerd

> Date: Sun, 23 Mar 2014 17:23:41 +0200
> From: marko.makela at iki.fi
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] Turn restrictions with role=via ways
> 
> On Sun, Mar 23, 2014 at 11:16:51AM +0100, Gerd Petermann wrote:
> >I don't care whether the restrictions could be changed in OSM. I just 
> >want to make sure that I translate them correctly we writing the img 
> >file.
> 
> IMO, this is on the border of "garbage in, garbage out". If there are 
> clear semantics of the role=via ways in turn restrictions that can be 
> easily explained to a human or a computer, sure, they can be supported.  
> It is a matter of finding balance of effort: will the implementation 
> effort be smaller than the effort to map it in a simpler way?
> 
> It also is a matter of risk: can the more complex translation rule fail 
> the "do what I mean" semantics that the mapper might have had in mind.  
> In the example of the only_right_turn restriction from the parking lot 
> driveway, we could accidentally introduce an only_straight_on 
> restriction to the main road (prohibiting any left turns). I think that 
> we would need some kind of regression tests for turn restrictions, or 
> routing in general.
> 
> These examples can be fixed in the map data, and I plan to do so in the 
> next few days. What cannot be fixed in the map data are no_u_turn 
> restrictions on dual-oneways that use role=via ways.
> 
> 	Marko
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