[OSM-talk] Good practices violated?

Toby Murray toby.murray at gmail.com
Thu May 30 04:25:12 UTC 2013


Yes, this is kind of tagging for the renderer however I believe there are
some legitimate technical reasons why it is needed - specifically with
administrative boundaries. The first thing that comes to mind is that while
rendering based on outlines seems nice, the centroid of a city/country is
not always where the label needs to be put. Take the USA for example. If
you compute the centroid of the entire boundary relation, Hawaii and Alaska
are going to pull it to the northwest and you will end up with a label that
is not in Kansas where it belongs. I suppose you could usually just use the
largest contiguous area to compute centroids for labels but it is a
complicated matter. And even then, it would diverge from what people expect
in many situations. Most maps put city labels in the social or economic
center of the city, not the centroid of the outline. In my city the
centroid would probably put the label in or near the university campus
which would be awkward on a map.

What has been done in a lot of situations is adding the node to the
relation with a role of "label" as an explicit rendering hint. In theory
the node would not need to be tagged with duplicate name/place information
if it is part of the relation but of course before any such change could
happen, tools would need to change first otherwise all city labels on
osm.org would vanish.

I am curious about your statement about names being rendered multiple
times. The only time I have seen this is with multipolygon relations. And
on Cyclemap where city labels *are* rendered based on the outlines instead
of the nodes. City exclaves each generate their own label which leads to
decidedly sub-optimal renderings like this:
http://www.openstreetmap.org/?lat=38.8226&lon=-97.617&zoom=12&layers=C

Toby




On Wed, May 29, 2013 at 7:54 PM, Jakub <j at kub.cz> wrote:

>  I do not want to sound too radical, but it is quite astonishing, how *Good
> practices <http://wiki.openstreetmap.org/wiki/Good_practice> can sometime
> radically differ from apparently widely accepted and even promoted usage.*Let me point out an example of what I mean, but I beleive that the problem
> is much wider than this particular case:
>
> *Countries on nodes vs areas vs relations*
>
> On one hand there is a:
>
>    - widely used practice to map country *both as node and relation* (and
>    sometimes area)
>    - suggestion that the place=country should be placed on node see Place<http://wiki.openstreetmap.org/wiki/Place>
>     - suggestion that  Key:place<http://wiki.openstreetmap.org/wiki/Key:place>should be used on node or area (relation not mentioned)
>    - suggestion to
>
> and on the other hand there is a:
>
>    - Principle Don't map for the renderer<http://wiki.openstreetmap.org/wiki/Tagging_for_the_renderer>- which is clearly violated by tagging node as a country, because country
>    is not a node and in fact this node is only ment for renderer (supported by
>    giving this node a label role in country relation)
>    - Principle One feature, one OSM element<http://wiki.openstreetmap.org/wiki/One_feature,_one_OSM_element>- which is clearly violated by fact that the tags are repeated both on node
>    and realtion (or area). This practice is not only used it is also
>    encouraged by wiki pages.
>
> Now, please do not get me wrong, I might be wrong and there might be some
> reason for that. If there is one, I would like to correct the documentation
> and rewrite Good practices (or list exceptions to them). If there is no
> reason I would like to clan up the data, but surely there should be some
> consensus on that and the consensus should be very well documented so there
> is not confusion in the future.
>
> Thanks for help
>
> Jakub
>
> PS: I beleive that this problem is much more general, it is also true with
> all sorts of regions, cities and villages. Names are rendered two or three
> times and is not good at all.
>
>
>
> _______________________________________________
> talk mailing list
> talk at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20130529/1b7252e6/attachment.html>


More information about the talk mailing list