[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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