[Talk-us] Complex intersection mapping

James Mast rickmastfan67 at hotmail.com
Sat Nov 9 02:47:26 UTC 2013


Martijn (and other telenav workers),

I just happened to see some intersections in my area tweaked today.  If you're going to be changing the intersections, can you at least please update the lane count on said ways if it's already been added at the same time?  I mean, if a way is on one side 4 lanes, and you split it into two separate ways, odds are both of them are 2 lanes each.  Yet, the lane count on them is still "4", which can also play screwy with the routing engines.

Also, can you please update any relations that are attached to the highways?  I'm going to bring up Changeset 18789658 as an example, which is the intersection of US-22 Business, PA-48, & the Orange Belt in Monroeville, PA.  The two numbered routes were "broken" today (amazingly the Orange Belt wasn't) with the change from a 1-point intersection to a 4-point intersection.  I personally think that a 1-point intersection was completely justified for this intersection because of only two directions being divided when exiting it.  Anyways, US-22 Business now has a gap because of the "new" ways for it, and PA-48 now doesn't end @ the intersection anymore because of the divided highway from the North being extended outside the main intersection.  And, to be honest, I'm also toying with the idea of reverting said changeset to repair the relations and make it a 1-point intersection again, but wanted to bring it up here on the list first before doing that to prevent an edit war.

So, if you keep doing it that way, can you please keep the collateral damage to a minimum when it comes to lane counts and highway relations?  I would really appreciate it when stuff like that was already tagged correctly doesn't need to be fixed again. :)


-James (rickmastfan67)


> From: martijnv at telenav.com
> Date: Mon, 14 Oct 2013 11:42:53 -0600
> To: talk-us at openstreetmap.org
> CC: stevec at telenav.com; kristenk at telenav.com; roberts at telenav.com; chrisz at telenav.com
> Subject: [Talk-us] Complex intersection mapping
> 
> 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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