[OSM-talk] colour fills in osmarender

[Etienne]

On 6/9/06, Andy Robinson <Andy_J_Robinson at blueyonder.co.uk> wrote:
<snip>
> Probably 50% of the ways I have created in residential Sutton Coldfield
have
> been non-linear, in that they contain loops, multiple branches and the
like.
> This is because I define my way as one which represents the contiguous
> physical street reference, normally its street name. If the named street
> forks then so do my ways.

I've been doing very much the same.  It works fine for rendering, but not
very useful for route planning.

There is a problem though even with rendering, that if a way has multiple
branches and the name is positioned half-way along the path of the way then
it may hit a discontinuous point and the name gets split into two fragments.

This can be solved by making each branch a separate way with just the "main"
way having a name (for rendering).  But this leaves the problem that the
branches are unnamed which could be disconcerting for residents of these
branches and for the postman ;-(

It seems like we need some method of making a collection of ways that are
all part of the same "road".  This could also deal with routes that are
discontinuous because of roundabouts, etc.

This would result in a schema that is something like:

 Road
  |
  |*
 Way
  |
  |*
 Node

Alternatively, segments could be extended to have contain an ordered list of
nodes so that we have:

 Way
  |
  |*
 Segment
  |
  |*
 Node

It's conceivable that the Road/Way/Segment should structure should be a
single class with hierarchical structure, but this would make it quite a bit
more difficult to process (for the average developer who is trying to
actually use the data).

               --------------
               |*           |
 Road/Way/Segment thingy    |
  |                        |                          |
  |            --------------
  | *
 Node

Rigth now, I'm pretty sure that what we have is not sufficient to describe
the data we need to model.  I don't know if what I'm suggesting is right
yet, but it does try to address some of the issues with the current model.

Etienne


>
> The result is, as Richard rightly pointed out, that what I have been
mapping
> for the physical world does not fit well with the algorithms required for
> path modelling (ie navigation).
>
> So, IMHO, OSM should record the physical and where this means that the
> representation of the physical in OSM does not fit with the ideals of the
> path models then something needs to be added to the nodes and segments
that
> permits the data to be used for path modelling. That could mean additional
> ways used for this purpose or additional tagging to segments and nodes for
> path analysis use.
>
> Cheers,
>
> Andy
>
> Andy Robinson
> Andy_J_Robinson at blueyonder.co.uk
>
> >-----Original Message-----
> >From: talk-bounces at openstreetmap.org [mailto:talk-
> >bounces at openstreetmap.org] On Behalf Of Etienne
> >Sent: 09 June 2006 11:46
> >To: sxpert at esitcom.org; talk at openstreetmap.org
> >Subject: Re: [OSM-talk] colour fills in osmarender
> >
> >On 6/9/06, Raphaël Jacquot <sxpert at esitcom.org> wrote:
> >> Etienne wrote:
> >>
> >> > Are loops and branches in ways a good thing or a bad thing?   I can
> >> > imagine that route planning applications might find them problematic,
> >> >
> >> > Etienne
> >>
> >> I believe we shouldn't have loops of any sort.
> >> routing algorithms like to have straight simple topologies. loops add a
> >> huge level of complexity that I don't think is necessary
> >
> >To do this, ways would need to be constrained so that segments can
> >only be contiguous within a way
> >(segment/@toNode=following-sibling::segment/@fromNode).  This would be
> >a good thing IMHO.
> >
> >However, if you don't have ways with loops and branches then you don't
> >really need segments at all.
> >
> >Some questions though:
> >
> >How would a roundabout be defined?  Is that a way or a point?
> >
> >Some roads, especially residential housing estates, can have roads
> >that split and merge and branch, but only have one name.  How can that
> >be achived economically?
> >
> >Etienne
> >
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> >talk at openstreetmap.org
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>
>
>
>
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