[OSM-talk] Islands

[80n]

On 4/16/07, Artem Pavlenko <artem at mapnik.org> wrote:
>
>
> On 16 Apr 2007, at 12:00, 80n wrote:
>
> On 4/16/07, Robert (Jamie) Munro <rjmunro at arjam.net> wrote:
> >
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > Artem Pavlenko wrote:
> > >
> > > 80n,
> > > We don't really need all this crossing segments.
> > > Please, could you explain to me what's wrong with representing
> > features
> > > like 'river with islands' as proper polygons (one exterior and
> > > n-interior rings) ? If you want just a small part of a bigger polygon
> > > for rendering use _clipping_.
> >
> > The problem is that none of our existing editors can cope well with
> > editing a way that is big and complicated e.g. the whole river Thames as
> > a single polygon. If it's multiple polygons, we need a way to join them,
> > which is the crossing segments. It's a similar problem to coastlines.
>
>
>
> No you don't need to join them.  You can use the feature/bug that ways do
> not require segments to be contiguous.  You can hop from one side of the
> river to the other and you can hop from the riverbank to an island without
> needing segments to connect them together.
>
> Logically a way is made up of one or more sub-paths.  Each non-contiguous
> segment implicitly defines the start of a new sub-path.
>
> If we ever get rid of segments then, in this scenario, the way would
> become a super-way and each sub-path would become a way.
>
> The concept of a path comprising of sub-paths is well defined in the W3C
> specifications and the rendering behaviour of such a path is also well
> defined.  It seems like a good model to use and is better than re-inventing
> the wheel (unless someone invents a better wheel).
>
> 80n
>
>
> Well, I'm not with you on this one!  Rendering is only one aspect of using
> OSM data. What about spatial analysis? Do you really suggesting to re-invent
> in that area?
>

Artem
Rendering is only one aspect of using OSM data.  What are the requirements
for spatial anaysis?  What needs to be represented in the OSM schema and
what is currently lacking?  What are you trying to achieve?

80n




Cheers,
> Artem
>
>
>
>
>
>
> Robert (Jamie) Munro
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v1.4.6 (Darwin)
> > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
> >
> > iD8DBQFGI1USz+aYVHdncI0RAlVMAJ9+gFeB0q23jLQFlyBHhXfZVod5ygCdGj9F
> > r9qMkGs42vUjaOTn7zJsS6k=
> > =fMVf
> > -----END PGP SIGNATURE-----
> >
>
>
> Artem Pavlenko
> http://mapnik.org
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20070416/6e6fa844/attachment.html>