See comments below:
David
------ Original Message ------
From: "Eric H. Christensen via Tagging" <tagging@openstreetmap.org>
To: "tagging@openstreetmap.org" <tagging@openstreetmap.org>
Cc: "Eric H. Christensen" <e...@aehe.us>
Sent: 18/11/2020 20:19:51
Subject: [Tagging] coastline v. water
After a few days of much work, a recent collaborative project to turn the
Chesapeake Bay from a nothing space outlined by natural=coastline to what we
considered to be a more accurate relation of natural=water, we've received some
negative feedback.
The difference of opinion seems to lie in the definition of what we're mapping. The use of
coastline is for "seas"[0] while the use of water is for "inland areas of
water"[1]. Even though the Chesapeake Bay is tidal, there is no question that it is an inland
waterway (it is completely surrounded by land except for the mouth at its southeast side).
Using this logic the Mediterranean Sea, the Red Sea, and the Persian
Gulf should all have the coastline tags removed from their defining ways
and converted to water areas! Italy, Greece, Libya, Egypt and a large
group of other counties would find they had no coastline, which might
come as a surprise to anyone lining there.
The idea of using coastlines for basically creating an edge between the land
and the nothingness of the ocean makes sense when, as far as the eye can see
it's only water.
Now, some of the feedback that has been presented[2] is that because it is
tidal it is part of the sea. I have pointed out that many rivers and streams
(and ditches!) are tidal; does that make them part of the sea? I would not
think so. In fact, there are named seas on this planet that are not even
connected to other water formations (the tiniest, according to the National
Geographic, is the Sea of Marmara which has an area just less than 12,950 sq
km, larger than the Chesapeake Bay).
But, tagging the Chesapeake Bay, and its tributaries, as "water" brings several
benefits to the map and the users. First, it helps identify the sections of water that
exist in these areas (this can't really be done with node points as there is no way to
define start and end points of an area). There are many defined bays, rivers, and
streams that make up the greater Chesapeake Bay area. What one may see as one large mass
of water is actually many smaller defined segments each with their own history.
This is irrelevant to the question of whether the ways should be tagged
as natural = coastline. You have had to create a multipolygon
containing the ways which form the "sections of water", its perfectly
possible to add the "name" tag to this multipolygon without removing the
coastline tag from the ways
Second, we can speed up any updates (fixes) to outlines of the polygons that
happen in these water areas without having to wait for the entire Earth's
coastlines to be re-rendered.
Changes to tagging should not be done to facilitate easier rendering on
one particular map.
I suspect having less coastline to render would also speed up the rendering of
coastlines as well?
Very unlikely.
I would like for the tagging community to clarify the different between "water" and
"coastline" and when to use each. The definition on water seems to say to use it on inland water
but there seems to be, at least, and open interpretation of the word "sea" for coastline that is
dragging many inland waters into that category.
Thanks,
Eric "Sparks" Christensen
[0] https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline
[1] https://wiki.openstreetmap.org/wiki/Tag:natural%3Dwater
[2] https://www.openstreetmap.org/changeset/94093155#map=10/37.1620/-76.1581
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