[Talk-us] Complex intersection mapping

Evin Fairchild evindfair at gmail.com
Tue Oct 15 02:09:32 UTC 2013

I too prefer the after pattern since it is easier to do, especially when
you are making a road be dual-carriageway by using the "parallel way"
feature in Potlatch 2. Also, it matches the way it is on the ground better.
Since there seems to be unanimous agreement to map intersections this way,
then I'll change other intersections to match.


On Mon, Oct 14, 2013 at 10:42 AM, Martijn van Exel <martijnv at telenav.com>wrote:

> Hi all,
> Here at Telenav we have been looking at complex intersections and we
> have set about editing some of these intersections in a way we feel
> represents the situation on the ground better than their original
> state, and because of that, works better for us. We have received some
> feedback on our edits so we wanted to take a step back and see what we
> (as the OSM community) think is the preferred way to map these
> intersections.
> So what are we talking about? Intersections like this one, where one
> or more dual carriageways come together at an at-grade intersection:
> https://www.evernote.com/shard/s9/sh/6438c196-bb92-4f66-81dc-9b75186286ba/0e8f07ff527c6a85c0dec426b9b79f1e
> One of my colleagues at Telenav has remapped this intersection as follows:
> https://www.evernote.com/shard/s9/sh/3491f1fe-6afa-4571-bc43-7cb31c9c2625/9dd47d1445fdcf03d3f0bbd93b8e0f92
> The main difference, and the source of some feedback we have received
> over the past few days, is that the dual carriageway roads are
> straightened out, creating multiple intersection nodes (4 in this
> case) instead of the original single intersection node that connects
> all the incoming and outgoing ways. That technique turns out to yield
> more reliable and correct routing and guidance ('keep left, turn
> right') through these intersections in our testing. But of course,
> that cannot dictate how we map as a community, so let's discuss.
> Some of the feedback we have received about these edits points to a
> statement on this wiki page:
> https://wiki.openstreetmap.org/wiki/TIGER_fixup#Braided_streets: 'It
> is a reasonable and well-used technique to bring the ways of dual
> carriageways back to a single point at intersections to facilitate and
> simplify the mapping of control devices and turn restrictions.' In my
> mapping across the US, my personal experience has been that this
> technique is in fact used, but the 'after' technique with straightened
> out ways is actually much more common. I personally prefer that
> technique as well - I think it is more pleasing to the eye, represents
> what is on the ground better, and is and easier to read. So my feeling
> was that this mapping practice would not be disputed. It turns out I
> was wrong, so I want to see what the consensus is on mapping
> intersections of this type - or perhaps there is none and we can work
> together to get there?
> Thanks,
> Martijn
> --
> Martijn van Exel
> OSM data specialist
> Telenav
> http://www.osm.org/user/mvexel
> http://wiki.openstreetmap.org/wiki/User:Mvexel
> http://hdyc.neis-one.org/?mvexel
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