[Tagging] Combining gas stations & convenience stores

Martin Vonwald imagic.osm at gmail.com
Sat Dec 13 09:56:48 UTC 2014


2014-12-12 17:28 GMT+01:00 fly <lowflight66 at googlemail.com>:
>
> Am 05.12.2014 um 21:30 schrieb Paul Johnson:
> > How about site relations?  Seems like a good use of a site relation.
>
> As long as it possible to draw the whole site as a single polygon, there
> is no need of a site relation.


Correct.

I would like to ask everyone to keep in mind that OSM data is usually
stored in some kind of spatial database. On core feature of any spatial
database is the ability to determine what features overlap others or what
feature(s) contain(s) specific other feature(s).

In short: a relation is never necessary if you simple want to know what
features are contained within an area. Just draw the area.

And never forget the biggest advantage of a simple area compared to a
relation: if you want to add a new feature and you used an area, you simply
add the new feature and you're done. If you used the relation, you need to
add the new feature also to the relation. If different mappers are
involved, it is very likely that one or the other forgets this - or doesn't
even know about it - and therefore breaks the relation.

The site relation is a good example of a often misused relation. It is only
necessary if the features of the "site" are spread over different places. I
seriously doubt that this would be true for most - if not all - gas
stations world wide.

br,
Martin
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