On 10/04/17 21:18, Paul Oldham wrote:
2. If not then can you explain why some of the border was not
previously tagged boundary=administrative plus admin_level=2 so that
I'm clear why it was done that way?
OK, well while I wait to see who pipes up I've been looking at this some
more.
I think, judging by the additional comment made by SK53 to the changeset
which started this off[1] after I'd posted here, that historically
boundary=administrative, admin_level=2 was used to tag ways and that
lead to exactly the problems we were seeing when rendering: that
sections of the boundary were simply missed out.
There's other problems I can see too with this method of tagging up
boundaries: ways could, and often would, be boundaries of things at
different admin levels (so both national and then probably several
levels of local government - so in UK terms county/district/parish - I
imagine there's something similar in Eire?) so admin levels are really
only useful for rendering (where lowest number wins with the default
styling), but not for giving information and even there they're less
than ideal.
So at some point (around the end of the last decade according SK53)
there seems to have been a move to tagging up relations for boundaries
rather than ways - and indeed that's what http://openstreetmap.org is
relying on for its rendering of the national borders).
All of which makes sense.
Now although I've been an occasional OSM contributor for quite a while
it's only recently that I've started doing more extensive work on OSM so
I rely heavily on the Wiki for guidance rather than what is clearly, to
some extent, a shared folk knowledge and this is where the problems arise.
For boundary=administrative the wiki says[2]:
The boundary=administrative tag is used on ways. It may also (or
instead) be used on a relation grouping several ways.
Which suggests, as it's currently written, that a way is where you would
normally find this tag.
However I've since discovered that if you look at the Relation:boundary
wiki page it says[3]:
Because boundaries can be rendered both from relations and individual
ways, tagging the ways is, in the strictest sense optional. There was
a render issue (see this Github discussion), but this was resolved.
So there the suggestion is that one should using relations for
boundaries and the tagging on ways is "in the strictest sense"
(interesting use of words there) optional.
Which is what we found before I began filling in the gaps and I think
answers my question (although I suspect from the tone of all of this
that in this case the optionality came about serendipitously rather than
through any plan.
So returning now to my first question:
1. Are you happy with what I've done?
And it seems to me, and I await correction natch, that what I've done is
in accord with the wiki although not strictly necessary. If so then I
can stop worrying ...
--
Paul
[1] http://www.openstreetmap.org/changeset/47540796
[2] http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative
[3] http://wiki.openstreetmap.org/wiki/Relation:boundary#Way_tags
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