[Tagging] Using multipolygons to map bays in Alaska

Graeme Fitzpatrick graemefitz1 at gmail.com
Sun Nov 18 01:41:52 UTC 2018

On Sun, 18 Nov 2018 at 05:09, Frederik Ramm <frederik at remote.org> wrote:

> Oh yes, certainly. Of course, in the concrete example at hand,
> re-tracing the whole boundary of the Gulf of Bothnia as a new way would
> have been worse (and impossible due to the 2000 node limit), and not
> even re-using the nodes would have been unspeakably worse.

On Sun, 18 Nov 2018 at 05:21, Christoph Hormann <osm at imagico.de> wrote:

> a possible partial conclusion here where most of us can agree on:  That
> bays and straits above a certain
> size - be that a few tens of km or even 100-200km - should not be
> mapped with a polygon.

On Sun, 18 Nov 2018 at 06:36, Paul Allen <pla16021 at gmail.com> wrote:

>  The node and area give different results in some circumstances and could,
> given
> improvements in rendering, give even greater differences in their output
> in the future.
> You point out that neither a new polygon that shares nodes with coastline
> ways nor a complex
> relationship are going to play nicely with the toolchain.  Being a bear of
> little brain, and lazy to
> boot, my first thought would be a crude polygon approximating the
> coastline.  It would have few
> enough nodes that it would be renderable but approximate the coastline
> sufficiently well for label
> placement.
> I still like a polygon even if the water in the bay looks no
> different from the ocean because using the query tool on the polygon will
> bring up an approximation
> to the extent of the bay.

Still following with interest & had a thought, which, although definitely
not a perfect answer, *may* (sort of!) satisfy everybody?

When we look at Bothnia, https://www.openstreetmap.org/#map=5/62.928/25.177,
the first thing I notice is the line of the 24 nautical mile (?)
international maritime boundary, in both the Bay & Gulf.

Would it work to use that boundary line as the outer of a very large, but
also quite simple polygon, as the boundary of the Gulf (or Bay) of Bothnia?

No, it's not perfect as the Bay should indeed meet the coastline, but it
will show that this area is the Bay of Bothnia.

Another question going back to the River Plate that I mentioned the other
day https://www.openstreetmap.org/#map=8/-35.131/-57.237.

It is clearly labelled as Rio de la Plata, but when you zoom in, the
labelling doesn't follow you eg

Should it?

If I want to zoom in & look at the waters of BA, then I'd like it to say
that i'm looking at the River Plate. Is that a system issue, or some thing
to do with Carto?


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