[Tagging] Coastline for rivers, estuaries and mangroves?

Colin Smale colin.smale at xs4all.nl
Mon Sep 10 07:44:09 UTC 2018


You suggest that coastline and baseline might be the same thing.
Unfortunately I, and many other people would take a different view. The
coastline (especially as used in OSM) is a geographically defined line,
that no law or declaration can change. It is normally taken to be
connected to the high water line. The baseline is however defined
politically, normally as a heavily generalised derivative of the low
water line, with rules (see UNCLOS and the Convention you referenced)
about how bays, islands, archipelagos, river mouths etc. can be factored
in to the resulting list of coordinates which is published to the world.
This baseline is the 0-line for the calculation of the 6/12 mile limits
and 200 mile EEZ. Watery bits on the land side of the baseline are
"internal waters" and are subject to the jurisdiction of the land (under
control of the local government). On the sea side of the baseline
maritime law will prevail, usually under control of the national
government in conjunction with all kinds of treaties. 

If the USA has defined the word "coastline" to mean "baseline", what
term does it use for the coastline in a geographic sense?

I believe that coastline and baseline are two different concepts which
need to be treated separately. If they happen to be colinear in some
cases, that's OK. But I am thinking here of vertical harbour walls,
where in 2D the high water line and low water line lay on top of one
another., and not some human declaration. 

We will need to be a little pragmatic, because OSM mappers are never
going to be able to do a proper survey of the coastline with the same
degree of accuracy as professional surveyors. We are limited to
leveraging existing data sources for all kinds of boundaries, other than
occasional anecdotal points. Trying to come up with our own definition
of things like coastline is a complete non-starter. The position of the
"river crossing" in the coastline should similarly follow existing
definitions. If we want to make further distinctions in our data so for
example salty water can be distinguished from fresh water, or so tidal
influence on river flow speed and direction can be represented, I am
sure the OSM community can find some suitable tagging for that, but that
is a separate issue to the COASTLINE discussion. 

On 2018-09-10 01:30, Graeme Fitzpatrick wrote:

> On Mon, 10 Sep 2018 at 08:25, Colin Smale <colin.smale at xs4all.nl> wrote: 
>> So are we getting any closer to consensus on where the coastline should cross the river? I think only if it is "somewhere between the tidal limit and the sea". Are all "crossing points" then equally valid? Or can we expect strong disagreements (especially at the limits) and possible edit wars?
> Unfortunately, I don't think we are ever all going to agree - some people are adamant about the tidal limit, while other's are equally convinced that it should be where the river enters the sea, & both arguments are just as logical as the other. 
> I think part of the problem is the lack of a precise definition of just what is the "coastline"? eg Merriam-Webster dictionary "a line that forms the boundary between the land and the ocean or a lake" which could well mean that the coastline goes up a river, but how far? 
> While searching for a better answer, I did however find this: http://www.myfloridalegal.com/ago.nsf/Opinions/E2D8E00068ACF5EE8525622F004AA168. 
> Some of the highlights include:  
> "Congress reacted to these decisions by enacting the Submerged Lands Act of 1953.[10] Congress defined "coast line" to mean "the line of ordinary low water along that portion of the coast which is in direct contact with the open sea and the line marking the seaward limit of inland waters" 
> "the Supreme Court set the meaning of "coast line" in its earlier decree.[32] The Court defined the term to mean "the line of ordinary low water along that portion of the coast which is in direct contact with the open sea and the line marking the seaward limits of inland waters."" 
> "During the late 1950s, the coastal countries of the world proposed, discussed, and drafted a treaty known as the Convention on the Territorial Sea and Contiguous Zone, April 29, 1958.[34] The hope was to provide uniformity in the delineation of the nations' territorial sea. Rather than using the term "coast line," the Convention used the term "baseline" in the measurement of the territorial sea. Article 3 defines the "baseline" for measuring the territorial sea as "the low water line along the coast as marked on large-scale charts officially recognized by the coastal State." The Convention was ratified by the United States in 1961 and became effective in 1964.[35] It is as a result of the Convention that the term "baseline" is used regarding coastline issues." 
> "By applying both the Convention and the Submerged Lands Act to Article X, section 16, Florida Constitution, the following results: 
> "A. 'Coastline' is the low water line that meets the shore along the coast of Florida which is in direct contact with the open sea. A coastline can never begin in open water; a coastline, in plain terms, is where the water meets the land." 
> Now, I would interpret all that as meaning that coastline & baseline are the same thing, so that the coastline should follow the line of the coast, cutting across the mouth of any rivers? 
> Thanks 
> Graeme 
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