[mkgmap-dev] [PATCH v3] heed the through_route relation when adjusting turn headings

Tue Feb 16 12:10:31 GMT 2010

Mark Burton wrote:
> v3 - bug fixes:
>
>  now ignores through_route relations if the junction is outside of the
>  tile's bounding box
>
>  should no longer think that ways that have been split do not start
>  or end at the junction.
>
>   

Mark - I've been giving the 'through_route' patch a bit of use, and I 
must say it does a great job of allowing the mapper to 'fix' those 
annoying junctions where there was no way for mkgmap to decide the road 
priority.

I have a couple of issues still, and a few suggestions:

1) Could you arrange for mkgmap to honour the "continuity" of a drawn 
way? In other words, if a way with a given name has a bend in it, and a 
stub of the same road class and same road name makes a "T" junction with 
it, then assume that the continuously-drawn way is the through-route? 
Here's an example:

http://www.openstreetmap.org/?mlat=51.577273&mlon=-4.041473&zoom=17&layers=B000FTF

..if you drive south-east on Kilfield Road, then as you approach the 
marker you'll be told to "turn right" where really the entire length of 
Kilfield Road is drawn as a single way, with the smaller stub being 
another way in its own right. I don't know about other mappers, but I 
know a *lot* of cases (mostly in residential areas) where a long curve 
of road had small stubs sticking off it, and they'll all generate bogus 
instructions if this isn't dealt with.

2) Can we invent some way to mark up traffic lanes? Here's a case in point:

http://www.openstreetmap.org/?mlat=51.61219&mlon=-3.961323&zoom=18&layers=B000FTF

You probably want to look at the area in Potlatch to see what's 
happening. Yes - I know I'm probably rather stretching the rules here, 
but the idea was that if a driver approaches on the A4067 from the east, 
wanting to take the right turn onto the stub of B4290 and thence to 
follow the B4290 towards the northeast, then he'd get a "keep right" 
instruction about 150m before the junction itself (that's where a 
dedicated traffic lane starts) and then get a "turn right" at the 
junction itself, followed by another "turn right" 30m later to the north 
as he joins the northeast-bound B4290.

It used to work like that, but now I get a "turn right" (not "keep 
right") at 150m short of the junction because the heading of the 
junction has been tweaked. If we could mark up traffic lanes it might 
allow you to maintain that useful "keep right" where the lane branches 
off. Additionally, one day we might find how "lane assist" works in 
Garmin maps and be able to code for it properly.

I wonder if marking a lane like this one as "highway=primary" 
"primary=traffic_lane" "ref=A4076" (etc) would be useful and desirable 
and would you be able to handle it anyway?

Steve