[Tagging] coastline v. water

Brian M. Sperlongano zelonewolf at gmail.com
Tue Nov 24 16:55:48 UTC 2020

> there were some attempts to suggest universally mapping bays with polygons
> rather than nodes previously:
> https://lists.openstreetmap.org/pipermail/tagging/2014-October/thread.html#19775
> which however never reached consensus because of the weighty arguments
> against this idea and because it was always clear that this would be a
> non-sustainable strategy for OSM in the long term.

It seems to me that consensus is achieved via three, often overlapping
methods, in no particular order:

1.  The proposal process
2.  What's documented on the wiki
3.  How tagging is actually used by mappers and data consumers

Specific discussions on the tagging lists are not necessarily good
indicators of consensus because they are often dominated by whomever
happens to be shouting the loudest and subscribed to the tagging list at
that moment.

With regard to mapping named bodies of water, possibly with fuzzy
boundaries, using polygons, the wiki documents that this is an acceptable
practice, as long as those polygons aren't too large (though, unhelpfully,
without defining what "too large" means).  As you note, osm-carto supports
this method of tagging for marginal seas, and mappers have adopted such

Thus, by wiki, and by actual tagging, and by data consumer usage, there IS
consensus - it is acceptable but not required to tag such things as
polygons.  We should not expect mappers to read the minds of people that
are subscribed to this list or comb through years of mailing list archives
to understand how tagging standards have evolved.  The history of how we
got here is irrelevant -- what matters is what exists now, what problems it
may or may not be causing, and what to do about it going forward.

Since you note that there is not a technical limitation, the argument seems
to boil down to "I don't like the standard of verifiability that other
mappers are using."  That is a perfectly valid opinion to have, but it does
not trump de facto, documented usage.  Given the community acceptance of
polygon mapping for smaller marginal seas, it would seem that a formal
proposal is the minimum standard required for documenting that there is
consensus to change de facto usage.

If this is a truly bad idea, and the arguments against such mapping are so
strong, it should be a no-brainer to draft a proposal laying out such
arguments so that the broader community can consider them and demonstrate
true consensus.
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