[OSM-talk] Fetch whole relation when parts of it are in bbox

[Robert (Jamie) Munro]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Jannis Achstetter wrote:
> Hello there,
> 
> I've got a problem with one specific tile:
> http://www.informationfreeway.org/?lat=49.974240779456515&lon=9.44955088920595&zoom=12&layers=0B00F000
> 
> You see that "inverted" tile right in the middle? This is actually not a
> bug in osmarender but in the API as far as I can see. I looked at the
> .osm-file it gets from the server and if I were the renderer I would
> have drawn it pretty the same as you can see this now. The problem is:
> We do have a multipolygon-relation here with the outer area (more than
> 1000 nodes) and some smaller areas which are no forests. Now I ask the
> API to give me the area and it does only return the smaller sub-areas,
> not the outer one (meaning: only a part of the relation). So, how do I
> know that these are no forests?
> Wouldn't it be good if the server would give me the whole relation and
> not only the parts that are inside the bbox? Would this introduce any
> problems for osmarender or other software?
> Technically I think this will not be a too huge problem since the server
> returns a whole way when only a part of it is inside the requested bbox,
> so why can't we do the same with relations?

Because relations can be big. You don't want to download the whole M1
motorway from London to Leeds just because you are working near Brent
Cross shopping centre. Also, do you then download all the relations of
all of the ways that you have downloaded?

No, this is a bad idea.

(personally, I think that returning all the nodes of a way even when
they are outside the bounding box is a bad idea unless you have actually
asked for them).

Robert (Jamie) Munro
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (Darwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFHLHihz+aYVHdncI0RAiJSAJ4uZsQIv+us97GH6Czyee4zXBUEEACeKLGY
r32EpbYZ3EFotQBbGEoQHtE=
=o5O8
-----END PGP SIGNATURE-----