[OSM-talk] Areas (was: Local map making - truncating ways on boundary?)
Frederik Ramm
frederik at remote.org
Sat Apr 5 03:02:49 BST 2008
Hi,
> Yes, I meant to say if every *polygon* which is represented as a closed
> way was guaranteed to have an "area=yes" tag or some other
> distinguishing feature.
You are right in saying that not having an explicit polygon type makes
OSM stick out from the standard OGC/ISO19100/whatever geometry models.
> And the reason for the area type not there is because it has not been
> used when it was there.
> Really? I never knew OSM had a polygon type.
It was called "area" and was supported by API 0.3. I think it was in the
API but not supported by JOSM and that's the reason nobody used it. The
reason it wasn't supported in JOSM was probably a misunderstanding
between SteveC and Imi, or at least that's what I've gathered. Remember,
that was a time when software development in the project was driven by
three or four people ,-) anyway, looking back doesn't help.
We have the following options:
1. re-instate the "area" type during the next API update.
2. create an independent data source that maps a set of tags to a
boolean "area" property. this data source might be a wiki page or SVN
file that is read by the processing software, or might even be a web
service. any software dealing with areas would use that service to know
what makes an area and what doesn't.
3. create a script that takes the planet file and uploads an added
"area=yes" to anything it considers an area.
4. modify the API to generate an "area=yes" tag on-the-fly whenever it
returns a way whose tags make it an area.
5. live with what we've got.
As you say, option 5 is a bit sub-optimal because stuff has to be
replicated everywhere. Personally I lean towards option 2; this would
still require replication of the "check tags against list" logic in all
applications but the list would come from a central source that's the
same for wall. I think we have similar "shared configuration" things
elsewhere and they seem to work.
Bye
Frederik
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