On Wed, Apr 4, 2018 at 7:40 AM, Eugene Alvin Villar <sea...@gmail.com> wrote:
> On Tue, Apr 3, 2018 at 9:22 PM, Martin Koppenhoefer <dieterdre...@gmail.com>
> wrote:
>> the coastline should represent the limit of the sea, in case of a river
>> flowing in, people look at the level of salt in the water and whether the
>> level of the river is influenced by tides (afaik)
> It seems some mappers go to the extreme opposite and map the coastline
> across the mouth of an estuary that is clearly part of the ocean:
> https://www.openstreetmap.org/way/186710973

How something is called and thought of by the locals is also taken into account.

Example: The Hudson River is hard to draw a firm boundary on. If one
were to take the position that "any shoreline with a measurable tide
is part of the coastline," then the coastline extends all the way up
to the Federal Dam in Troy, New York:

It's still obviously a river up there. The water is fresh, and flows
quite strongly in one direction. (When the tide is rising, it flows a
little less strongly. It never reverses.)

Drawing the salt front would be ambiguous by tens of km. In a wet
season, its a highly diffuse front near the entrance to the Tappan Zee
(note to self: make a relation for the waterbody!)
https://www.openstreetmap.org/way/318106482 but in a drought it can
retreat as far as the Poughkeepsie Bridge
https://www.openstreetmap.org/way/24185107 or even farther. Even where
it's brackish, it's still called a 'river,' and if you said that it
was 'coastline,' the locals would look at you as if you had two heads.

People seem to agree that the piers in Manhattan where the big ships
dock are on the coast, so the line is drawn somewhat arbitrarily north
of Spuyten Duyvil https://www.openstreetmap.org/way/135719690.

I'm not going to say that the local mappers are wrong, even though the
estuary is deep enough that vessels of considerable draft can sail
into Albany. There's a WW2-vintage destroyer moored there on
more-or-less permanent display. She got there under her own steam. In
historic times, the Albany riverfront would display a small forest of
ships' masts - but it's always been called a riverport, not a seaport.
A sailing vessel would have to kedge the faster sections of the river.
I pity those who had to man the capstan.

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