[Talk-us] Separate relations for each direction of US & State highways.

[Martijn van Exel]

This should go live pretty soon:

https://github.com/openstreetmap/openstreetmap-website/pull/543



On Thu, Nov 21, 2013 at 12:00 PM, Martijn van Exel <martijnv at telenav.com> wrote:
> The patch has been merged into master and should make it into the next
> iD release.
>
> On Thu, Nov 21, 2013 at 11:03 AM, Martijn van Exel <martijnv at telenav.com> wrote:
>> That is a really good and interesting point, Chris. I just confirmed
>> that iD leaves the north / south / east / west roles alone when
>> reversing a way. Neither does Potlatch (although Potlatch does not
>> seem to actually allow you to reverse a way, just to flip the oneway=
>> between 1 and -1).
>> At least iD would need to be patched for this, I would say. I
>> submitted one: https://github.com/systemed/iD/pull/2004
>>
>> On Thu, Nov 21, 2013 at 1:27 AM, Chris Lawrence <lordsutch at gmail.com> wrote:
>>> On Wed, Nov 20, 2013 at 2:32 PM, Martijn van Exel <martijnv at telenav.com>
>>> wrote:
>>>>
>>>> Reading through this I see that most are in favor of avoiding dividing
>>>> relations more than necessary: no separate relations for directions,
>>>> especially not if the geometry is the same for both.
>>>>
>>>> That leaves the question of how to tag cardinal directions? As I said
>>>> before, I think the role tag is suitable for this. It's already used
>>>> pretty widely (with around 100k ways having a cardinal direction as
>>>> the role tag in a relation), documented
>>>> (https://wiki.openstreetmap.org/wiki/Route#Members) and it replaces
>>>> the forward / backward role values that are not particularly useful or
>>>> meaningful.
>>>> I created a stub of a wiki page that we could use to describe the
>>>> preferred tagging in more detail:
>>>>
>>>> http://wiki.openstreetmap.org/wiki/Highway_Directions_In_The_United_States.
>>>> (The current content is geared towards using the member role tag, but
>>>> this can be changed depending on the outcome of this discussion.)
>>>
>>>
>>> The only problem I can anticipate with this tagging scheme is that it's
>>> possible some editors don't understand anything other than
>>> left/right/forward/backward (I think), we could end up in data loss
>>> situations fairly easily.
>>>
>>> For example: way X pointing east is marked in relation Y as "east"
>>> (presumably we could assume that "east" = forward and the opposite cardinal
>>> direction "west" is backward). User reverses way X. Now the relation role is
>>> potentially backward.  JOSM seems to understand at least north/south and
>>> east/west and offers to fix it (see
>>> http://josm.openstreetmap.de/browser/josm/trunk/src/org/openstreetmap/josm/corrector/ReverseWayTagCorrector.java);
>>> no idea if iD or Potlatch do.
>>>
>>> We'd also need to make the validation tools smarter to recognize lossage
>>> (for example, realizing that the route is unbroken only if the chain of role
>>> tags once you account for the directions of the underlying ways is
>>> monotonic),
>>>
>>>
>>> Chris
>>> --
>>> Chris Lawrence <lordsutch at gmail.com>
>>>
>>> Website: http://www.cnlawrence.com/
>>>
>>> _______________________________________________
>>> Talk-us mailing list
>>> Talk-us at openstreetmap.org
>>> https://lists.openstreetmap.org/listinfo/talk-us
>>>
>>
>>
>>
>> --
>> --
>> 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
>
>
>
> --
> --
> 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



-- 
--
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