Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Kevin]

I've worked extensively with the National Wetlands Inventory (NWI) from
the U.S. Fish & Wildlife Service. I think it may be helpful (maybe) to look
at the way they delineate estuarine and marine habitats. Their
classification methods are described in this document...

https://www.fws.gov/wetlands/documents/Classification-of-Wetlands-and-Deepwater-Habitats-of-the-United-States-2013.pdf

the pertinent Estuarine section...

Limits. The Estuarine System extends (1) upstream and landward to where
ocean-derived
salts measure less than 0.5 ppt during the period of average annual low
flow; (2) seaward
to an imaginary line closing the mouth of a river, bay, or sound; and (3)
to the seaward
limit of wetland emergents, shrubs, or trees where they are not included in
(2). The
Estuarine System also includes offshore areas of continuously diluted sea
water.

the pertinent Marine section...

Definition. The Marine System (Figure 2) consists of the open ocean
overlying the
continental shelf and its associated high-energy coastline. Marine habitats
are exposed to
the waves and currents of the open ocean and the Water Regimes are
determined
primarily by the ebb and flow of oceanic tides. Salinities exceed 30 parts
per thousand
(ppt), with little or no dilution except outside the mouths of estuaries.
Shallow coastal
indentations or bays without appreciable freshwater inflow, and coasts with
exposed
rocky islands that provide the mainland with little or no shelter from wind
and waves, are
also considered part of the Marine System because they generally support
typical marine
biota.

Limits. The Marine System extends from the outer edge of the continental
shelf
shoreward to one of three lines: (1) the landward limit of tidal inundation
(extreme high
water of spring tides), including the splash zone from breaking waves; (2)
the seaward
limit of wetland emergents, trees, or shrubs; or (3) the seaward limit of
the Estuarine
System, where this limit is determined by factors other than vegetation.
Deepwater
habitats lying beyond the seaward limit of the Marine System are outside
the scope of the
WCS.

I think the key idea here is "high-energy" vs "low-energy" which would
allow a mapper to identify exposed coasts subject to wave action, etc,
versus a more protected river or bay.



Kevin

On Thu, Sep 13, 2018 at 2:42 PM, Kevin Kenny 
wrote:

> [Off list, I've had my say on list]
>
> > In the past, it was decided that the coastline would represent the high
> tide line, and the first OSM mappers generally put the coastline up at the
> tidal limit of rivers (which were easy to verify for them, because there is
> usually a dam or weir at that location in England).
>
> That's entirely sensible for Great Britain.
>
> And it matches my local situation, except for where the coastline is drawn
> - and for the immense scale of the difference.  The Hudson River (and the
> problem repeats itself for rivers such as the Delaware and Susquehanna) has
> an extremely long estuary. It's really unclear that the English rule makes
> sense for it. That's why I've been arguing for leaving room for a modicum
> of judgment on the part of the local mappers.
>
> The Hudson is definitely estuarine, with tidal ranges up to a couple of
> metres, for its entire lower reach.  The traditional 'mouth' of the river
> is an east-west line from the Battery, the southern tip of Manhattan
> Island, and this is labeled as 'mile zero' by the boatmen. The river
> continues to be tidal, flowing about six hours onshore and six hours
> offshore, all through its lower reach. Even in a dry summer, it's virtually
> never 'salt' (defined as 100 mg chloride per litre) in surface water beyond
> mile 60 (kilometre 97), although denser salt water persists at depth
> farther up. The salt front has not, in living memory, retreated past mile
> 75 (kilometre 121) - above there, it can be thought of as being perennially
> fresh water, although continuing to reverse direction above that point.
>
> As I said, the flow is about equally divided in terms of time, but the
> flow rates on ebb and flow vary widely - the river water, after all, does
> eventually reach the sea. By Haverstraw (about 60 km from the river mouth)
> the ebb runs about twice as fast as the flow, and that's as far upstream as
> tidal currents present a navigational hazard. (Canoeists and kayakers had
> better be aware of the direction of the tide, since few can make progress
> upstream paddling against a Hudson River ebb!)
>
> The river remains navigable by moderately-deep-draught vessels all the way
> to Albany. A Super-Panamax or larger ship cannot use Albany as a port of
> call, but the Port of Albany does see a fair amount of oceangoing traffic.
> It can accommodate a ship 289 metres in length, 33.5 metres in width, and
> 9.5 metres in draught. Its fixed cranes can lift 225 tonnes, and 1000-tonne
> barge-mounted cranes are available. Still, it's unquestionably a riverport
> - the draught of a ship has to be de-rated f

Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Kevin Kenny]

[Off list, I've had my say on list]

> In the past, it was decided that the coastline would represent the high
tide line, and the first OSM mappers generally put the coastline up at the
tidal limit of rivers (which were easy to verify for them, because there is
usually a dam or weir at that location in England).

That's entirely sensible for Great Britain.

And it matches my local situation, except for where the coastline is drawn
- and for the immense scale of the difference.  The Hudson River (and the
problem repeats itself for rivers such as the Delaware and Susquehanna) has
an extremely long estuary. It's really unclear that the English rule makes
sense for it. That's why I've been arguing for leaving room for a modicum
of judgment on the part of the local mappers.

The Hudson is definitely estuarine, with tidal ranges up to a couple of
metres, for its entire lower reach.  The traditional 'mouth' of the river
is an east-west line from the Battery, the southern tip of Manhattan
Island, and this is labeled as 'mile zero' by the boatmen. The river
continues to be tidal, flowing about six hours onshore and six hours
offshore, all through its lower reach. Even in a dry summer, it's virtually
never 'salt' (defined as 100 mg chloride per litre) in surface water beyond
mile 60 (kilometre 97), although denser salt water persists at depth
farther up. The salt front has not, in living memory, retreated past mile
75 (kilometre 121) - above there, it can be thought of as being perennially
fresh water, although continuing to reverse direction above that point.

As I said, the flow is about equally divided in terms of time, but the flow
rates on ebb and flow vary widely - the river water, after all, does
eventually reach the sea. By Haverstraw (about 60 km from the river mouth)
the ebb runs about twice as fast as the flow, and that's as far upstream as
tidal currents present a navigational hazard. (Canoeists and kayakers had
better be aware of the direction of the tide, since few can make progress
upstream paddling against a Hudson River ebb!)

The river remains navigable by moderately-deep-draught vessels all the way
to Albany. A Super-Panamax or larger ship cannot use Albany as a port of
call, but the Port of Albany does see a fair amount of oceangoing traffic.
It can accommodate a ship 289 metres in length, 33.5 metres in width, and
9.5 metres in draught. Its fixed cranes can lift 225 tonnes, and 1000-tonne
barge-mounted cranes are available. Still, it's unquestionably a riverport
- the draught of a ship has to be de-rated for the fresh water, and it's a
long sail up to there. It's chiefly used for bulk cargo from upstate New
York and neighbouring Canada, and for project cargoes such as heavy
electrical equipment from GE Energy in Schenectady.

Most of the lower reach of the Hudson has very little tidal change to its
spatial extent. It's in a narrow valley between two highlands, and both
banks are cliffy.  (The view across the river from Manhattan is quite
spectacular.) The water moves up and down, but has little room to expand
from side to side.


The tidal limit is the 'Federal Dam' (actually a weir by OSM definitions,
since there's a full-width spillway) in Troy, so just as in the UK, we have
a well defined fall line marking the transition from estuary to true river
- at river mile 153 (246 km).  The locals think that extending the
'coastline' upriver nearly 250 km from what is traditionally regarded as
the river mouth is little short of insane. Even if you were to place the
'mouth' of the Severn somewhere near Cardiff, for instance, a comparable
distance up the river would bring you, at the very least, well past
Shrewsbury and perhaps even to the headwaters. Great Britain simply has no
estuaries of nearly that magnitude.

All this leaves me with no clue, in OSM terms, what to call the thing.
Mostly, I don't call it at all. It might answer. :)


On Thu, Sep 13, 2018 at 3:42 AM Joseph Eisenberg 
wrote:

> Re: "Data consumers have a right to being able to interpret the data as
> the mapper intended"
>
> For data users, it would be most useful if the coastline is in a
> consistent position in relation to the sea and land, clearly.
>
> In the past, it was decided that the coastline would represent the high
> tide line, and the first OSM mappers generally put the coastline up at the
> tidal limit of rivers (which were easy to verify for them, because there is
> usually a dam or weir at that location in England).
>
> But perhaps we need to start adding second line to represent the average
> low tide, to define the intertidal zone. Right now the only way to see if
> an area is in the intertidal zone is if a natural area has been tagged
> outside of the coastline. This works for shoals, beaches and wetlands, but
> it's a little ambiguous. If we start mapping the low tide line, this will
> clearly show the interidal zone. This outer line could also be defined to
> cut across rivers and estuaries at the mouth, similar to

Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

Re: "Data consumers have a right to being able to interpret the data as the
mapper intended"

For data users, it would be most useful if the coastline is in a consistent
position in relation to the sea and land, clearly.

In the past, it was decided that the coastline would represent the high
tide line, and the first OSM mappers generally put the coastline up at the
tidal limit of rivers (which were easy to verify for them, because there is
usually a dam or weir at that location in England).

But perhaps we need to start adding second line to represent the average
low tide, to define the intertidal zone. Right now the only way to see if
an area is in the intertidal zone is if a natural area has been tagged
outside of the coastline. This works for shoals, beaches and wetlands, but
it's a little ambiguous. If we start mapping the low tide line, this will
clearly show the interidal zone. This outer line could also be defined to
cut across rivers and estuaries at the mouth, similar to how political
baselines are defined (however, it would not be arbitarily defined like the
baseline). The part of the river between the OSM coastline and the "low
tide line" would represent an estuary.

Thinking about the limits of the intertidal zone would make it clear that
the high tide line (=coastline in OSM) should not be a tangent across the
mouth of an estuary. A brackish estuary is a boundary environment between
marine and fresh water, just like the intertidal zone is transitional
between land and sea.

The high tide line or coastline then would define the largest extent of the
marine environment and the minimum extent of land plus inland waters. The
low tide line could, in contrast, show the smallest extent of the marine
environment and the largest possible definition of inland waters.

In this case, I would think it would make sense to start mapping water
areas for estuaries. Even though the water would be outside the coastline
(and therefore already could be rendered with no problems), mapping the
area of estuaries and intertidal waters would clearly define the size of
estuaries and the extent of this zone.

I know that in the past, others have said that defining estuaries would
just create 2 limit problems: you would have to decide where the estuary
turns into river and where it turns into sea, while setting the coastline
is just one decision. But this would be a compromise that lets everyone get
their preferred data, and allows 3 color of lakes / rivers / sea. In fact,
a renderer could choose to render estuaries the same as river, or the same
as sea, or even as a gradient between the two, because they would be
defined. Right now, with varying locations of the coast it's not feasible
to render rivers and sea differently with OSM data, and it's not possible
to measure the size of estuaries directly.

Would these advantages be worth the extra work of tracing a second line
along the coast?

Joseph Eisenberg

On Tue, Sep 11, 2018 at 4:34 PM Colin Smale  wrote:

> On 2018-09-11 08:27, Graeme Fitzpatrick wrote:
>
> 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
> I agree, but we also can't easily say where the tidal limit reaches?
>
>
> In most cases the state mapping or hydrography agency will know. They have
> the gear, the knowledge and the mandate to make that determination.
>
> but that is a separate issue to the COASTLINE discussion.
>>
> Maybe, but personally, I still think that the river banks shouldn't be
> marked as coastline, & that the coastline should cut across the river at
> the coast, so I guess we may agree to continue disagreeing :-)
>
>
> I guess so, but what is at stake here is not getting you or me to change
> our minds, but to define what the word means in an OSM context. Mappers may
> also disagree about the definition of "highway" (including or excluding the
> grassy bits?) but IMHO data consumers have a right to being able to
> interpret the data as the mapper intended. If different mappers use a tag
> in differing ways, how is the consumer to know the intention? Having
> differing conventions for each country is just about doable, but if
> individual mappers all have their own definitions, the data becomes less
> valuable. There is much discussion and debate about selected tagging
> topics, but the only thing that really counts is the result, conclusion,
> consensus etc that should come out of it. Unfortunately it rarely does, and
> that saddens me.  OSM is broadening its reach to more and more parts of the
> world, and that is good, but there needs to be equal effort put in to the
> depth of data and the quality (consistency) of the data.
>
> Cheers,
> Colin
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-11 08:27, Graeme Fitzpatrick wrote:

> 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 
> I agree, but we also can't easily say where the tidal limit reaches?

In most cases the state mapping or hydrography agency will know. They
have the gear, the knowledge and the mandate to make that determination.


>> but that is a separate issue to the COASTLINE discussion.
> 
> Maybe, but personally, I still think that the river banks shouldn't be marked 
> as coastline, & that the coastline should cut across the river at the coast, 
> so I guess we may agree to continue disagreeing :-)

I guess so, but what is at stake here is not getting you or me to change
our minds, but to define what the word means in an OSM context. Mappers
may also disagree about the definition of "highway" (including or
excluding the grassy bits?) but IMHO data consumers have a right to
being able to interpret the data as the mapper intended. If different
mappers use a tag in differing ways, how is the consumer to know the
intention? Having differing conventions for each country is just about
doable, but if individual mappers all have their own definitions, the
data becomes less valuable. There is much discussion and debate about
selected tagging topics, but the only thing that really counts is the
result, conclusion, consensus etc that should come out of it.
Unfortunately it rarely does, and that saddens me.  OSM is broadening
its reach to more and more parts of the world, and that is good, but
there needs to be equal effort put in to the depth of data and the
quality (consistency) of the data. 

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Graeme Fitzpatrick]

On Mon, 10 Sep 2018 at 17:45, Colin Smale  wrote:

> Graeme,
>
> You suggest that coastline and baseline might be the same thing.
>
I'm not disagreeing with you, Colin, just trying to make sense of the whole
thing! :-)

It appears that Florida has decided that they do match, but as Martin &
Warin pointed out, sometimes that just doesn't work - I've seen the same
thing near here in Australia, where the baseline cuts across the mouth of a
bay, so that a few '00 klm's of "coast" aren't included.

One thing I would think though, using the often-referenced cry of local
knowledge ...

Go anywhere in the World, walk up to a River & ask the local standing there
fishing what it's course is.

I'm pretty certain that you'll be told that "It rises back up there in the
Hinterland, comes down across the plain here & runs out to Sea at River
Heads" or similar.

I'd be very (!) surprised if anybody (except a very dedicated OSM mapper!)
would start detailing that it rises as a spring, which forms a rivulet,
becomes a stream, then a river (or creek?) which then becomes a tidal
inlet, with the tide reaching 11.5 klms upstream? No, I think they'd say
we're standing here on the riverbank & the mouth of the river is down
there, where it reaches the sea?

If the USA has defined the word "coastline" to mean "baseline", what term
> does it use for the coastline in a geographic sense?
>
Sorry, no idea?


> 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
>
I agree, but we also can't easily say where the tidal limit reaches?

> but that is a separate issue to the COASTLINE discussion.
>
Maybe, but personally, I still think that the river banks shouldn't be
marked as coastline, & that the coastline should cut across the river at
the coast, so I guess we may agree to continue disagreeing :-)

Thanks

Graeme
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Warin]

On 10/09/18 19:25, Martin Koppenhoefer wrote:
2018-09-10 10:41 GMT+02:00 Colin Smale >:


The baseline is defined by the state, in accordance with the
UNCLOS rules, and published to the world by deposition with the
UN. The basis for the baseline is: "the normal baseline for
measuring the breadth of the territorial sea is the low-water line
along the coast as marked on large-scale charts officially
recognized by the coastal State."
http://www.un.org/depts/los/convention_agreements/texts/unclos/part2.htm





is there also a definition for an "unnormal" or exceptional baseline? 
E.g. here: http://www.nonnodondolo.it/userfiles/image/37(1).gif 

you can see that e.g. the whole gulf of taranto is included by the 
baseline https://en.wikipedia.org/wiki/Gulf_of_Taranto
From what I have seen, although there is the UN definition about the 
low water line, actual baselines tend to be much more "generous". The 
baselie is what the country self declares and other countries 
accept/recognize.


Also the 12nmi extension (territorial waters) is not always the same, 
some countries pretend(ed) 200 nautical miles.





Fiji (an island nation) baseline encloses;

Land = 18,272 sq. kilometers

Internal waters = 25,558 sq. kilometers

Archipelagic waters = 130,470 sq. kilometers


I'd think that most people would agree that their baseline is a long way 
from what they would consider a coast line.



https://www.state.gov/documents/organization/58567.pdf
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-10 11:34, Colin Smale wrote:

> On 2018-09-10 11:25, Martin Koppenhoefer wrote: 
> 
> 2018-09-10 10:41 GMT+02:00 Colin Smale :
> 
> The baseline is defined by the state, in accordance with the UNCLOS rules, 
> and published to the world by deposition with the UN. The basis for the 
> baseline is: "the normal baseline for measuring the breadth of the 
> territorial sea is the low-water line along the coast as marked on 
> large-scale charts officially recognized by the coastal State." 
> http://www.un.org/depts/los/convention_agreements/texts/unclos/part2.htm 
> is there also a definition for an "unnormal" or exceptional baseline? E.g. 
> here: http://www.nonnodondolo.it/userfiles/image/37(1).gif 
> you can see that e.g. the whole gulf of taranto is included by the baseline 
> https://en.wikipedia.org/wiki/Gulf_of_Taranto 
> From what I have seen, although there is the UN definition about the low 
> water line, actual baselines tend to be much more "generous". The baselie is 
> what the country self declares and other countries accept/recognize. 
> Also the 12nmi extension (territorial waters) is not always the same, some 
> countries pretend(ed) 200 nautical miles.

Up to 200nm is the EEZ (Exclusive Economic Zone), that's not the same.
There's a neat explanation and diagram here: 
https://sites.tufts.edu/lawofthesea/chapter-two/ 

The situation with the Gulf of Taranto is that Italy claims it is an
"historic bay" for which the convention indeed makes an exception. What
constitutes an "historic bay" is not defined in the Convention
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-10 11:25, Martin Koppenhoefer wrote:

> 2018-09-10 10:41 GMT+02:00 Colin Smale :
> 
>> The baseline is defined by the state, in accordance with the UNCLOS rules, 
>> and published to the world by deposition with the UN. The basis for the 
>> baseline is: "the normal baseline for measuring the breadth of the 
>> territorial sea is the low-water line along the coast as marked on 
>> large-scale charts officially recognized by the coastal State." 
>> http://www.un.org/depts/los/convention_agreements/texts/unclos/part2.htm
> 
> is there also a definition for an "unnormal" or exceptional baseline? E.g. 
> here: http://www.nonnodondolo.it/userfiles/image/37(1).gif 
> you can see that e.g. the whole gulf of taranto is included by the baseline 
> https://en.wikipedia.org/wiki/Gulf_of_Taranto 
> From what I have seen, although there is the UN definition about the low 
> water line, actual baselines tend to be much more "generous". The baselie is 
> what the country self declares and other countries accept/recognize. 
> 
> Also the 12nmi extension (territorial waters) is not always the same, some 
> countries pretend(ed) 200 nautical miles.

Up to 200nm is the EEZ (Exclusive Economic Zone), that's not the same.
There's a neat explanation and diagram here: 

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Martin Koppenhoefer]

2018-09-10 10:41 GMT+02:00 Colin Smale :

>
> The baseline is defined by the state, in accordance with the UNCLOS rules,
> and published to the world by deposition with the UN. The basis for the
> baseline is: "the normal baseline for measuring the breadth of the
> territorial sea is the low-water line along the coast as marked on
> large-scale charts officially recognized by the coastal State."
>
> http://www.un.org/depts/los/convention_agreements/texts/unclos/part2.htm
>



is there also a definition for an "unnormal" or exceptional baseline? E.g.
here: http://www.nonnodondolo.it/userfiles/image/37(1).gif
you can see that e.g. the whole gulf of taranto is included by the baseline
https://en.wikipedia.org/wiki/Gulf_of_Taranto
>From what I have seen, although there is the UN definition about the low
water line, actual baselines tend to be much more "generous". The baselie
is what the country self declares and other countries accept/recognize.

Also the 12nmi extension (territorial waters) is not always the same, some
countries pretend(ed) 200 nautical miles.


Cheers,
Martin
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-10 10:30, Martin Koppenhoefer wrote:

>> On 10. Sep 2018, at 02:09, Joseph Eisenberg  
>> wrote:
>> 
>> The legal definition of the baseline is the low tide line and also cuts 
>> across bays, inlets and estuaries.
> 
> I thought the baseline was generally defined politically/legally. In Italy 
> for example there is a law which contains a long list of points (many with 
> coordinates).

Both are correct. 

The baseline is defined by the state, in accordance with the UNCLOS
rules, and published to the world by deposition with the UN. The basis
for the baseline is: "the normal baseline for measuring the breadth of
the territorial sea is the low-water line along the coast as marked on
large-scale charts officially recognized by the coastal State." 

http://www.un.org/depts/los/convention_agreements/texts/unclos/part2.htm___
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Martin Koppenhoefer]

sent from a phone

> On 10. Sep 2018, at 02:09, Joseph Eisenberg  
> wrote:
> 
> The legal definition of the baseline is the low tide line and also cuts 
> across bays, inlets and estuaries.


I thought the baseline was generally defined politically/legally. In Italy for 
example there is a law which contains a long list of points (many with 
coordinates).


cheers,
Martin
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

Graeme, 

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  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 follow

Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

The legal definition of the baseline is the low tide line and also cuts
across bays, inlets and estuaries.

But OSM has always marked the coastline at the mean high water line, and
that is also the line shown on most maps. It is also much easier to verify
than the low water baseline, which by definition is in the sea 99% of the
time.

I believe the German language Wiki page mentions that the baseline can be
marked as an administrative boundary, because it is a legal fiction, not a
geographical feature of the landscape.

In the past a few people have mentioned adding the low water line as a
second feature in addition to the coastline, but so far people have beeen
individually drawing shoals, mud flats, beaches and other wetlands befoyond
the coastline, which seems sufficient to me.

On Mon, Sep 10, 2018 at 8:31 AM Graeme Fitzpatrick 
wrote:

>
>
> On Mon, 10 Sep 2018 at 08:25, Colin Smale  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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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Graeme Fitzpatrick]

On Mon, 10 Sep 2018 at 08:25, Colin Smale  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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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-09 23:35, David Groom wrote:

> -- Original Message -- 
> From: "Joseph Eisenberg"  
> To: tagging@openstreetmap.org 
> Sent: 07/09/2018 04:02:26 
> Subject: Re: [Tagging] Coastline for rivers, estuaries and mangroves? 
> 
>> I've now edited the coastline in the area mentioned. I have now added 
>> natural=coastline along all the ways forming the edge of the mangroves and 
>> open water. 
>> https://www.openstreetmap.org/changeset/62340975#map=13/-4.9075/137.1762
> 
> I have to say that to me this seems wrong. Coastline tags are now on ways 
> forming channels 40m wide and 30km from open ocean.  I just don't see that 
> these are "coastlines" .

Those distances are not too dissimilar to the situation on the River
Dart, where this whole discussion started. 

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
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[David Groom]

-- Original Message --
From: "Joseph Eisenberg" 
To: tagging@openstreetmap.org
Sent: 07/09/2018 04:02:26
Subject: Re: [Tagging] Coastline for rivers, estuaries and mangroves?

I've now edited the coastline in the area mentioned. I have now added 
natural=coastline along all the ways forming the edge of the mangroves 
and open water. 
https://www.openstreetmap.org/changeset/62340975#map=13/-4.9075/137.1762


I have to say that to me this seems wrong. Coastline tags are now on 
ways forming channels 40m wide and 30km from open ocean.  I just don't 
see that these are "coastlines" .


David




Further west, I moved the administrative boundary off of the coastline 
of internal waterways, positioning it near the low water line / 
baseline, because I believe this is closer to the official Indonesian 
definition for Kabupaten (admin level 6) boundaries, and it no longer 
creates separate polygons around each patch of mangroves. 
https://www.openstreetmap.org/changeset/62344890#map=14/-4.8615/136.8500


This brought up another issue. I did not want to delete the 
natural=water areas, so I changed them to multipolygons (since I had to 
break the closed ways to make a proper coastline) and marked salt=yes, 
removing natural=river from the areas that might better be described as 
tidal channels. I considered using water=tidal or water=salt, but both 
of these tags seem to have limited use and an unclear definition; JOSM 
suggested salt=yes.


But I am uncertain what to do with the waterway=river in the case of 
tidal channels and the complex connections between rivers in these 
mangrove areas. A search of taginfo did not find an alternative tag, 
although river=tidal is in use. I think there should still be a 
waterway midline for the large tidal channels in the mangroves which 
can be used by boats or even ships, to help navigation software. (Many 
of these channels were actually created by flowing river water; the 
rivers in this area meander strongly and often change the location of 
the mouth, as can be seen by comparing the current situation to 100 
year old Dutch maps)


Perhaps waterway=river with tidal=yes or river=tidal is the best option 
to prevent tag fragmentation? Or is river=tidal_channel preferable? The 
problem is determining the direction of water flow when two channels 
connect. Besides tidal, is there a better tag to imply two-way water 
flow depending on the tidal cycle?


Joseph



Message: 3
Date: Wed, 5 Sep 2018 18:03:36 +0200
From: Christoph Hormann 
To: "Tag discussion, strategy and related tools"
        
Subject: Re: [Tagging] Coastline for rivers, estuaries and mangroves?
Message-ID: <201809051803.36467@imagico.de>
Content-Type: text/plain;  charset="utf-8"

On Wednesday 05 September 2018, Joseph Eisenberg wrote:
> Specific examples:
>
> 1) This changeset on the River Dart in southwest England was the
> source of the Help site question:
> https://www.openstreetmap.org/changeset/61959067

The coastline closure there:

https://www.openstreetmap.org/way/216482240

is both below the lower limit of the proposal and below the the range 
i

can imagine a meaningful coastline closure rule to allow.

I would however be interested in hearing any universal rule that would
allow this kind of placement based on physically observable criteria
and that would maintain the coastline as a meaningful geometry on its
own.

> It looks like quite a large estuary, much wider than the non-tidal
> part of the river upstream.

That is largely not really an estuary but more of a ria.  I have no 
data

for this at hand but you can likely see an abrupt change in the
elevation profile near Totnes where the submerged section of the 
former

river valley starts.  So in this case it would make a lot of sense to
place the coastline closure near the upper end of the tidal section
because this is much better defined in terms of physical geography.

> 2) The estuaries and mangrove tidal channels in this area:
> https://www.openstreetmap.org/#map=11/-4.8806/136.9339

Here i likewise see no meaningful motivation for the current coastline
placement - like here:

https://www.openstreetmap.org/way/614052686

Poor image quality in the available sources makes identifying the 
limit

of the mangroves difficult, you really need to make use of available
lower resolution open data images in the area for proper maiing here.
But you can conclude a few thing from the structure of the network of
channels.  For example

https://www.openstreetmap.org/relation/7301266

is quite clearly not a river but a tidal channel (there is no river
feeding it, it is just draining seawater that has entered during
raising tide).

> I previously changed the coastline to be closer to the river mouths
> in another section of coast to the southeast, but perhaps I should
> change it back? The whole idea of coastline around mangrove swamps 
is

> m

Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Graeme Fitzpatrick]

On Mon, 10 Sep 2018 at 04:43, Christoph Hormann  wrote:

> I would probably use waterway=tidal_channel since the term 'creek' which
> i think you have correctly identified as the English language term for
> this is ambiguous ('creek' as you also say is also used for inland
> waterways).  The German term is 'Priel' which is clearer but would be
> useless and confusing for those who don't speak German.
>
> Yes, drawing a line between a tidal channel and a river is difficult but
> the purpose would be to offer mappers an option in cases where
> waterway=river is clearly not correct, not to allow doubt free
> decisions in all boundary cases.
>

How about:
waterway=inlet
tidal=yes
salt=yes

https://en.wikipedia.org/wiki/Inlet

Thanks

Graeme
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Sunday 09 September 2018, Joseph Eisenberg wrote:
>
> So I would favor a tagging scheme that would allow waterway=river as
> the top=level tag. Also, I believe making new top-level tags is
> discouraged.

Using waterway=river for something that is definitely not a river would 
devalue existing data with this tag by blurring its meaning - i don't 
think that is a good idea.

I would probably use waterway=tidal_channel since the term 'creek' which 
i think you have correctly identified as the English language term for 
this is ambiguous ('creek' as you also say is also used for inland 
waterways).  The German term is 'Priel' which is clearer but would be 
useless and confusing for those who don't speak German.

Yes, drawing a line between a tidal channel and a river is difficult but 
the purpose would be to offer mappers an option in cases where 
waterway=river is clearly not correct, not to allow doubt free 
decisions in all boundary cases.

-- 
Christoph Hormann
http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

Martin, are you saying we need a new top level waterway=* tag? What would
you use? Perhaps waterway=yes? That would be the most generic option,
perhaps too broad? Or waterway=marine ? Waterway=tidal?

The correct English term for these features is variable. In southwest
England, they are called creeks (or tidal creeks), or pills. Creek is also
used for water channels between mangroves in India and Pakistan. But in
other areas they are called tidal channels or tidal inlets. See this
Wikipedia article for all the examples:
https://en.wikipedia.org/wiki/Creek_(tidal)

This makes it hard to decide on a specific tag. "Creek" would be a poor
choice, because some dialects use this word to refer to small freshwater
rivers (or large streams), including most of North America. That's why I
was inclinded to use a more general tagging scheme.

On Sun, Sep 9, 2018 at 7:08 PM Martin Koppenhoefer 
wrote:

>
>
> sent from a phone
>
> > On 9. Sep 2018, at 07:00, Joseph Eisenberg 
> wrote:
> >
> > What do you all think about using waterway=river & river=tidalchannel
> for water channels in mangroves?
>
>
> IMHO we could have a tag for channels which could be applied also
> elsewhere and which is not river (rivers are usually freshwater, tagging
> tidal channels as rivers seems strange)
>
>
> cheers,
> Martin
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Martin Koppenhoefer]

sent from a phone

> On 9. Sep 2018, at 07:00, Joseph Eisenberg  wrote:
> 
> What do you all think about using waterway=river & river=tidalchannel for 
> water channels in mangroves?


IMHO we could have a tag for channels which could be applied also elsewhere and 
which is not river (rivers are usually freshwater, tagging tidal channels as 
rivers seems strange)


cheers,
Martin
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

Way 570038402, named "Rute", is certainly different in appearance than the
"tidal channels" / rivers through the mangroves in my area. "Rute" is a
V-shaped channel of deeper water between shoals or tidal mud flats, and the
coast is clearly a long way off. I can see how this shouldn't be labeled as
a river.

The channels between mangroves, however, can look almost the same as a real
river, whether from aerial imagery, when flying over, or from a boat at sea
level. The water flow may reverse with the tide if the river water flow is
slow. The only way to determine if a given channel is a "real" river is to
follow it upstream to the end of mangroves, which may be dozens of
kilometers away, or carefully measure salinity and average current. This
makes it difficult to verify in person or when looking at a limited area in
an editor.

Because of these problem, it's not surprising that many people have been
marking the narrow water channels between mangroves as waterway=river, and
I don't think this will stop happening.

So I would favor a tagging scheme that would allow waterway=river as the
top=level tag. Also, I believe making new top-level tags is discouraged.

What do you all think about using waterway=river & river=tidalchannel for
water channels in mangroves? (I would also suggest adding tidal=yes &
salt=yes to fit with existing tags for describing water bodies such as
tidal rivers and salt lakes)

Or would it be sufficient to use tidal=yes & salt=yes with waterway=river,
without any new tag, for these waterways through the mangroves?

-Joseph Eisenberg in Papua, Indonesia

On Sat, Sep 8, 2018 at 6:35 PM Christoph Hormann  wrote:

> On Saturday 08 September 2018, Graeme Fitzpatrick wrote:
> >
> > Question for you though in regard to these "non-rivers"?
> >
> > Are these channels permanent or do they move as tidal runoff changes?
>
> Between mangroves these are fairly static but elsewhere they can change
> quite rapidly.
>
> > & they appear to be named? At least 570038402 is marked as "Rute",
> > running through "Ruteplate". My translate has failed me as all it
> > comes up with for Rute is rod, stick, cane & similar which doesn't
> > make any sense for a waterway? Is there another meaning for Rute, or
> > is it possibly a local name?
>
> Naming of tidal channels is quite common but like most maritime naming
> you will often have a hard time to define a geometric verifiability.
> Therefore most geometries drawn here are subjective label placement
> sketches.  In mangrove areas this is a bit different of course.
>
> But i don't want to discourage anyone from a actually defining new tags
> here - just make sure you document them in a verifiable form.
>
> --
> Christoph Hormann
> http://www.imagico.de/
>
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Saturday 08 September 2018, Graeme Fitzpatrick wrote:
>
> Question for you though in regard to these "non-rivers"?
>
> Are these channels permanent or do they move as tidal runoff changes?

Between mangroves these are fairly static but elsewhere they can change 
quite rapidly.

> & they appear to be named? At least 570038402 is marked as "Rute",
> running through "Ruteplate". My translate has failed me as all it
> comes up with for Rute is rod, stick, cane & similar which doesn't
> make any sense for a waterway? Is there another meaning for Rute, or
> is it possibly a local name?

Naming of tidal channels is quite common but like most maritime naming 
you will often have a hard time to define a geometric verifiability.  
Therefore most geometries drawn here are subjective label placement 
sketches.  In mangrove areas this is a bit different of course.

But i don't want to discourage anyone from a actually defining new tags 
here - just make sure you document them in a verifiable form.

-- 
Christoph Hormann
http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Graeme Fitzpatrick]

On Fri, 7 Sep 2018 at 21:35, Christoph Hormann  wrote:

>
> This only applies for the seaward continuation of a river, for a tidal
> channel without any significant freshwater inflow waterway=river would
> be wrong - like here:
>
> https://www.openstreetmap.org/way/401730961
> https://www.openstreetmap.org/way/401730966
> https://www.openstreetmap.org/way/570038402


Thanks for clarifying things Christoph

Question for you though in regard to these "non-rivers"?

Are these channels permanent or do they move as tidal runoff changes?

& they appear to be named? At least 570038402 is marked as "Rute", running
through "Ruteplate". My translate has failed me as all it comes up with for
Rute is rod, stick, cane & similar which doesn't make any sense for a
waterway? Is there another meaning for Rute, or is it possibly a local
name?

 Thanks

Graeme
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Friday 07 September 2018, Joseph Eisenberg wrote:
> But I am uncertain what to do with the waterway=river in the case of
> tidal channels and the complex connections between rivers in these
> mangrove areas. A search of taginfo did not find an alternative tag,
> although river=tidal is in use. I think there should still be a
> waterway midline for the large tidal channels in the mangroves which
> can be used by boats or even ships, to help navigation software.
> (Many of these channels were actually created by flowing river water;
> the rivers in this area meander strongly and often change the
> location of the mouth, as can be seen by comparing the current
> situation to 100 year old Dutch maps)

There is no requirement of river lines to end at the coastline - plenty 
of situations where this is not the case and the documentation also 
explicitly mentions the possibility:

https://www.openstreetmap.org/way/5005576
https://www.openstreetmap.org/way/487506679
https://www.openstreetmap.org/way/550322860

This only applies for the seaward continuation of a river, for a tidal 
channel without any significant freshwater inflow waterway=river would 
be wrong - like here:

https://www.openstreetmap.org/way/401730961
https://www.openstreetmap.org/way/401730966
https://www.openstreetmap.org/way/570038402

This - just like polygon mapping of similar features:

https://www.openstreetmap.org/way/559890030
https://www.openstreetmap.org/way/559890031
https://www.openstreetmap.org/way/425143314
https://www.openstreetmap.org/way/425186522
https://www.openstreetmap.org/way/291218813

can be considered label placement mapping without any real verifiable 
meaning.  If you want to map such things with a geometry other than a 
node you should first create a verifiable definition of the geometry 
(which seems hard) - otherwise you always end up with this kind of 
label drawing.

-- 
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

I've now edited the coastline in the area mentioned. I have now added
natural=coastline along all the ways forming the edge of the mangroves and
open water.
https://www.openstreetmap.org/changeset/62340975#map=13/-4.9075/137.1762

Further west, I moved the administrative boundary off of the coastline of
internal waterways, positioning it near the low water line / baseline,
because I believe this is closer to the official Indonesian definition for
Kabupaten (admin level 6) boundaries, and it no longer creates separate
polygons around each patch of mangroves.
https://www.openstreetmap.org/changeset/62344890#map=14/-4.8615/136.8500

This brought up another issue. I did not want to delete the natural=water
areas, so I changed them to multipolygons (since I had to break the closed
ways to make a proper coastline) and marked salt=yes, removing
natural=river from the areas that might better be described as tidal
channels. I considered using water=tidal or water=salt, but both of these
tags seem to have limited use and an unclear definition; JOSM suggested
salt=yes.

But I am uncertain what to do with the waterway=river in the case of tidal
channels and the complex connections between rivers in these mangrove
areas. A search of taginfo did not find an alternative tag, although
river=tidal is in use. I think there should still be a waterway midline for
the large tidal channels in the mangroves which can be used by boats or
even ships, to help navigation software. (Many of these channels were
actually created by flowing river water; the rivers in this area meander
strongly and often change the location of the mouth, as can be seen by
comparing the current situation to 100 year old Dutch maps)

Perhaps waterway=river with tidal=yes or river=tidal is the best option to
prevent tag fragmentation? Or is river=tidal_channel preferable? The
problem is determining the direction of water flow when two channels
connect. Besides tidal, is there a better tag to imply two-way water flow
depending on the tidal cycle?

Joseph


> Message: 3
> Date: Wed, 5 Sep 2018 18:03:36 +0200
> From: Christoph Hormann 
> To: "Tag discussion, strategy and related tools"
>     
> Subject: Re: [Tagging] Coastline for rivers, estuaries and mangroves?
> Message-ID: <201809051803.36467@imagico.de>
> Content-Type: text/plain;  charset="utf-8"
>
> On Wednesday 05 September 2018, Joseph Eisenberg wrote:
> > Specific examples:
> >
> > 1) This changeset on the River Dart in southwest England was the
> > source of the Help site question:
> > https://www.openstreetmap.org/changeset/61959067
>
> The coastline closure there:
>
> https://www.openstreetmap.org/way/216482240
>
> is both below the lower limit of the proposal and below the the range i
> can imagine a meaningful coastline closure rule to allow.
>
> I would however be interested in hearing any universal rule that would
> allow this kind of placement based on physically observable criteria
> and that would maintain the coastline as a meaningful geometry on its
> own.
>
> > It looks like quite a large estuary, much wider than the non-tidal
> > part of the river upstream.
>
> That is largely not really an estuary but more of a ria.  I have no data
> for this at hand but you can likely see an abrupt change in the
> elevation profile near Totnes where the submerged section of the former
> river valley starts.  So in this case it would make a lot of sense to
> place the coastline closure near the upper end of the tidal section
> because this is much better defined in terms of physical geography.
>
> > 2) The estuaries and mangrove tidal channels in this area:
> > https://www.openstreetmap.org/#map=11/-4.8806/136.9339
>
> Here i likewise see no meaningful motivation for the current coastline
> placement - like here:
>
> https://www.openstreetmap.org/way/614052686
>
> Poor image quality in the available sources makes identifying the limit
> of the mangroves difficult, you really need to make use of available
> lower resolution open data images in the area for proper maiing here.
> But you can conclude a few thing from the structure of the network of
> channels.  For example
>
> https://www.openstreetmap.org/relation/7301266
>
> is quite clearly not a river but a tidal channel (there is no river
> feeding it, it is just draining seawater that has entered during
> raising tide).
>
> > I previously changed the coastline to be closer to the river mouths
> > in another section of coast to the southeast, but perhaps I should
> > change it back? The whole idea of coastline around mangrove swamps is
> > most confusing. I don't think the mangroves should be outside of the
> > coastline, but where then should it be?
>
> Common practice i

Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Wednesday 05 September 2018, Joseph Eisenberg wrote:
> Specific examples:
>
> 1) This changeset on the River Dart in southwest England was the
> source of the Help site question:
> https://www.openstreetmap.org/changeset/61959067

The coastline closure there:

https://www.openstreetmap.org/way/216482240

is both below the lower limit of the proposal and below the the range i 
can imagine a meaningful coastline closure rule to allow.

I would however be interested in hearing any universal rule that would 
allow this kind of placement based on physically observable criteria 
and that would maintain the coastline as a meaningful geometry on its 
own.

> It looks like quite a large estuary, much wider than the non-tidal
> part of the river upstream.

That is largely not really an estuary but more of a ria.  I have no data 
for this at hand but you can likely see an abrupt change in the 
elevation profile near Totnes where the submerged section of the former 
river valley starts.  So in this case it would make a lot of sense to 
place the coastline closure near the upper end of the tidal section 
because this is much better defined in terms of physical geography.

> 2) The estuaries and mangrove tidal channels in this area:
> https://www.openstreetmap.org/#map=11/-4.8806/136.9339

Here i likewise see no meaningful motivation for the current coastline 
placement - like here:

https://www.openstreetmap.org/way/614052686

Poor image quality in the available sources makes identifying the limit 
of the mangroves difficult, you really need to make use of available 
lower resolution open data images in the area for proper maiing here.  
But you can conclude a few thing from the structure of the network of 
channels.  For example

https://www.openstreetmap.org/relation/7301266

is quite clearly not a river but a tidal channel (there is no river 
feeding it, it is just draining seawater that has entered during 
raising tide).

> I previously changed the coastline to be closer to the river mouths
> in another section of coast to the southeast, but perhaps I should
> change it back? The whole idea of coastline around mangrove swamps is
> most confusing. I don't think the mangroves should be outside of the
> coastline, but where then should it be?

Common practice is to place the coastline at the outer end of the 
mangrove forest.  This is a pragmatic solution because placing it 
inside the mangrove would be non-verifiable.  Of course mapping the 
mangrove is important for the data to be meaningful in this case.

-- 
Christoph Hormann
http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

Specific examples:

1) This changeset on the River Dart in southwest England was the
source of the Help site question:
https://www.openstreetmap.org/changeset/61959067

It looks like quite a large estuary, much wider than the non-tidal
part of the river upstream. User keithonearth, who made the edit, was
looking for discussion on this. (It looks like this was just discussed
on the GB list as well:
https://lists.openstreetmap.org/pipermail/talk-gb/2018-August/021885.html
)

2) The estuaries and mangrove tidal channels in this area:
https://www.openstreetmap.org/#map=11/-4.8806/136.9339

I previously changed the coastline to be closer to the river mouths in
another section of coast to the southeast, but perhaps I should change
it back? The whole idea of coastline around mangrove swamps is most
confusing. I don't think the mangroves should be outside of the
coastline, but where then should it be?

-Joseph

> Date: Wed, 5 Sep 2018 09:29:03 +0200
> From: Christoph Hormann 
> To: "Tag discussion, strategy and related tools"
>   
> Subject: Re: [Tagging] Coastline for rivers, estuaries and mangroves?
> Message-ID: <201809050929.03882@imagico.de>
> Content-Type: text/plain;  charset="utf-8"
>
> On Wednesday 05 September 2018, Joseph Eisenberg wrote:
>> Colin and Christoph, could you give some guidance about a couple of
>> the specific situations that I brought up in the original post?
>>
>> First, in the question on the help Q&A board, the other mapper wanted
>> to remove the coastline from tidal parts of rivers in England , so
>> that the end of the waterway=river would meet the coastline. It looks
>> to me that this is contrary to standard mapping in England and many
>> other places. But I can see why some people look at the waterway line
>> out beyond the coastline and feel it needs the river area mapped.
>
> I think you need to give specific examples for a meaningful discussion
> here.
>
>> It seems like this would be reasonable, if the coastline is
>> considered to map the furthest inland limit of the marine environment
>> (at high tide), and the river area plus the line of the waterway are
>> mapping the longest extention of the river.
>
> To be clear:  The upper limit of tidal influence on water levels and the
> ecological limit of the marine environment are two very different
> things.  Tidal influence often goes much further upstream - as
> illustrated by Kevin's example.
>
> --
> Christoph Hormann
> http://www.imagico.de/
>
>
>

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Wednesday 05 September 2018, Joseph Eisenberg wrote:
> Colin and Christoph, could you give some guidance about a couple of
> the specific situations that I brought up in the original post?
>
> First, in the question on the help Q&A board, the other mapper wanted
> to remove the coastline from tidal parts of rivers in England , so
> that the end of the waterway=river would meet the coastline. It looks
> to me that this is contrary to standard mapping in England and many
> other places. But I can see why some people look at the waterway line
> out beyond the coastline and feel it needs the river area mapped.

I think you need to give specific examples for a meaningful discussion 
here.

> It seems like this would be reasonable, if the coastline is
> considered to map the furthest inland limit of the marine environment
> (at high tide), and the river area plus the line of the waterway are
> mapping the longest extention of the river.

To be clear:  The upper limit of tidal influence on water levels and the 
ecological limit of the marine environment are two very different 
things.  Tidal influence often goes much further upstream - as 
illustrated by Kevin's example.

-- 
Christoph Hormann
http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

Colin and Christoph, could you give some guidance about a couple of
the specific situations that I brought up in the original post?

First, in the question on the help Q&A board, the other mapper wanted
to remove the coastline from tidal parts of rivers in England , so
that the end of the waterway=river would meet the coastline. It looks
to me that this is contrary to standard mapping in England and many
other places. But I can see why some people look at the waterway line
out beyond the coastline and feel it needs the river area mapped.

Would mapping the water area of the river all the way down to the
mouth be a good solution? This would be extra work in the ID editor,
but quite simple in JOSM. It would lead to having two ways on the
riverbank from the mouth to the end of the coastline: both
natural=coastline and natural=water (or waterway=riverbank), but then
it would be easier to calculate the total surface area of a river
include it's estuary and tidal portions, for example.

It seems like this would be reasonable, if the coastline is considered
to map the furthest inland limit of the marine environment (at high
tide), and the river area plus the line of the waterway are mapping
the longest extention of the river.

Has this method been used extensively?
-Joseph Eisenberg


Date: Mon, 03 Sep 2018 23:40:02 +0200
From: Colin Smale 
To: tagging@openstreetmap.org
Subject: Re: [Tagging] Coastline for rivers, estuaries and mangroves?

>On 2018-09-03 23:08, Christoph Hormann wrote:

>> On Monday 03 September 2018, Colin Smale wrote: This is essentially the 
>> situation we have right now.  Judgement of
>> local mappers is usually fine (with the exception of political
>> cases like the Rio de la Plata).  Most problems occur because
>> armchair mappers misinterpret the local situation or when
>> inexperienced mappers are unaware of the significance of
>> distinguishing between ocean and riverbank mapping.
>> What guidance do we give to the local mappers?

>What is currently written on the wiki which includes the proposal which
>is linked to from the coastline documentation.

>> Given a properly formulated rule-of-thumb, why should remote armchair
>> mappers come to a different conclusion to local mappers in this case?

>As said this is mostly due to misinterpreting imagery.

That can account for a few metres either way (perpendicular to the
shoreline), but not for the difference between tidal limit and a
"convenient crossing point near the sea". That is purely a personal
judgement, not misaligning imagery. After all, we are not disputing here
the location of the sides of the river, but where we draw the line from
one side of the river to the other.

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

Graeme, 

Baseline is not the same as coastline, so the definition you refer to is
not what we are looking for. 

Coastline is a geographic feature, and is normally based on high water. 

Baseline is a political feature, based on the low water mark, and
simplified around bays, inlets and islands. This is the baseline from
which the 12nm territorial limit is measured, and also the 200nm EEZ and
median lines if applicable. Water on the landward side of the baseline
(e.g. lakes, inlets, estuaries) is referred to as internal waters, i.e.
belonging to the land mass itself for the purposes of maritime law.

On 2018-09-03 23:58, Graeme Fitzpatrick wrote:

> This has recently been discussed on the Australian list, with reference being 
> made to 
> http://www.ga.gov.au/scientific-topics/marine/jurisdiction/maritime-boundary-definitions,
>  which is based on the UN Convention on the Law of the Sea 
> http://www.un.org/Depts/los/convention_agreements/convention_overview_convention.htm.
>  
> 
> For our discussion now: 
> 
> "TERRITORIAL SEA BASELINE
> 
> The term Territorial Sea Baseline (TSB) refers to the line from which the 
> seaward limits of Australia's Maritime Zones are measured. These include the 
> breadth of the territorial sea; the seaward limits of the contiguous zone, 
> the exclusive economic zone and, in some cases, the continental shelf. 
> 
> The territorial sea baseline may be of various types depending upon the shape 
> of the coastline in any given locality: 
> 
> * The Normal baseline corresponds with the low water line along the coast, 
> including the coasts of islands. Under the Convention, normal baseline can be 
> drawn around low tide elevations which are defined as naturally formed areas 
> of land surrounded by and above water at low tide but submerged at high tide, 
> provided they are wholly or partly within 12 nautical miles of the coast. For 
> Australian purposes, normal baseline corresponds to the level of Lowest 
> Astronomical Tide (LAT) [1].
> * Straight baselines are a system of straight lines joining specified or 
> discrete points on the low-water line, usually known as straight baseline end 
> points. These may be used in localities where the coastline is deeply 
> indented and cut into, or where there is a fringe of islands along the coast 
> in its immediate vicinity.
> * Bay or river closing lines are straight lines drawn between the respective 
> low-water marks of the natural entrance points of bays or rivers.
> 
> Waters on the landward side of the baseline are internal waters for the 
> purposes of international law." 
> 
> & NB that they say that the Normal baseline is the low water line! 
> 
> The UN's definitions: 
> 
> Straight baselines 
> 
> 1. In localities where the coastline is deeply indented and cut into, or if 
> there is a fringe of islands along the coast in its immediate vicinity, the 
> method of straight baselines joining appropriate points may be employed in 
> drawing the baseline from which the breadth of the territorial sea is 
> measured. 
> 
> 2. Where because of the presence of a delta and other natural conditions the 
> coastline is highly unstable, the appropriate points may be selected along 
> the furthest seaward extent of the low-water line and, notwithstanding 
> subsequent regression of the low-water line, the straight baselines shall 
> remain effective until changed by the coastal State in accordance with this 
> Convention. 
> 
> 3. The drawing of straight baselines must not depart to any appreciable 
> extent from the general direction of the coast, and the sea areas lying 
> within the lines must be sufficiently closely linked to the land domain to be 
> subject to the regime of internal waters. 
> 
> 4. Straight baselines shall not be drawn to and from low-tide elevations, 
> unless lighthouses or similar installations which are permanently above sea 
> level have been built on them or except in instances where the drawing of 
> baselines to and from such elevations has received general international 
> recognition. 
> 
> 5. Where the method of straight baselines is applicable under paragraph 1, 
> account may be taken, in determining particular baselines, of economic 
> interests peculiar to the region concerned, the reality and the importance of 
> which are clearly evidenced by long usage. 
> 
> 6. The system of straight baselines may not be applied by a State in such a 
> manner as to cut off the territorial sea of another State from the high seas 
> or an exclusive economic zone. 
> 
> Article9 
> 
> Mouths of rivers 
> 
> If a river flows directly into the sea, the baseline shall be a straight line 
> across the mouth of the river between points on the low-water line of its 
> banks.
> 
> So, unless any of us want to argue with the UN, or suggest that they change 
> their definitions to suit OSM! :-), I think that they could be counted as the 
> final word? 
> 
> Thanks 
> 
> Graeme 
> __

Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Graeme Fitzpatrick]

This has recently been discussed on the Australian list, with reference
being made to
http://www.ga.gov.au/scientific-topics/marine/jurisdiction/maritime-boundary-definitions,
which is based on the UN Convention on the Law of the Sea
http://www.un.org/Depts/los/convention_agreements/convention_overview_convention.htm
.

For our discussion now:
"Territorial Sea Baseline

The term Territorial Sea Baseline (TSB) refers to the line from which the
seaward limits of Australia's Maritime Zones are measured. These include
the breadth of the territorial sea; the seaward limits of the contiguous
zone, the exclusive economic zone and, in some cases, the continental shelf.

The territorial sea baseline may be of various types depending upon the
shape of the coastline in any given locality:

   - The Normal baseline corresponds with the low water line along the
   coast, including the coasts of islands. Under the Convention, normal
   baseline can be drawn around low tide elevations which are defined as
   naturally formed areas of land surrounded by and above water at low tide
   but submerged at high tide, provided they are wholly or partly within 12
   nautical miles of the coast. For Australian purposes, normal baseline
   corresponds to the level of Lowest Astronomical Tide (LAT)
   

   .
   - Straight baselines are a system of straight lines joining specified or
   discrete points on the low-water line, usually known as straight baseline
   end points. These may be used in localities where the coastline is deeply
   indented and cut into, or where there is a fringe of islands along the
   coast in its immediate vicinity.
   - Bay or river closing lines are straight lines drawn between the
   respective low-water marks of the natural entrance points of bays or rivers.

Waters on the landward side of the baseline are internal waters for the
purposes of international law."

& NB that they say that the Normal baseline is the low water line!


The UN's definitions:

Straight baselines

1. In localities where the coastline is deeply indented and cut into, or if
there is a fringe of islands along the coast in its immediate vicinity, the
method of straight baselines joining appropriate points may be employed in
drawing the baseline from which the breadth of the territorial sea is
measured.

2. Where because of the presence of a delta and other natural conditions
the coastline is highly unstable, the appropriate points may be selected
along the furthest seaward extent of the low-water line and,
notwithstanding subsequent regression of the low-water line, the straight
baselines shall remain effective until changed by the coastal State in
accordance with this Convention.

3. The drawing of straight baselines must not depart to any appreciable
extent from the general direction of the coast, and the sea areas lying
within the lines must be sufficiently closely linked to the land domain to
be subject to the regime of internal waters.

4. Straight baselines shall not be drawn to and from low-tide elevations,
unless lighthouses or similar installations which are permanently above sea
level have been built on them or except in instances where the drawing of
baselines to and from such elevations has received general international
recognition.

5. Where the method of straight baselines is applicable under paragraph 1,
account may be taken, in determining particular baselines, of economic
interests peculiar to the region concerned, the reality and the importance
of which are clearly evidenced by long usage.

6. The system of straight baselines may not be applied by a State in such a
manner as to cut off the territorial sea of another State from the high
seas or an exclusive economic zone.

Article9

Mouths of rivers

If a river flows directly into the sea, the baseline shall be a straight
line across the mouth of the river between points on the low-water line of
its banks.
So, unless any of us want to argue with the UN, or suggest that they change
their definitions to suit OSM! :-), I think that they could be counted as
the final word?

Thanks

Graeme
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-03 23:08, Christoph Hormann wrote:

> On Monday 03 September 2018, Colin Smale wrote: This is essentially the 
> situation we have right now.  Judgement of
> local mappers is usually fine (with the exception of political
> cases like the Rio de la Plata).  Most problems occur because
> armchair mappers misinterpret the local situation or when
> inexperienced mappers are unaware of the significance of
> distinguishing between ocean and riverbank mapping. 
> What guidance do we give to the local mappers?

What is currently written on the wiki which includes the proposal which 
is linked to from the coastline documentation.

> Given a properly formulated rule-of-thumb, why should remote armchair
> mappers come to a different conclusion to local mappers in this case?

As said this is mostly due to misinterpreting imagery. 

That can account for a few metres either way (perpendicular to the
shoreline), but not for the difference between tidal limit and a
"convenient crossing point near the sea". That is purely a personal
judgement, not misaligning imagery. After all, we are not disputing here
the location of the sides of the river, but where we draw the line from
one side of the river to the other.___
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Monday 03 September 2018, Colin Smale wrote:
> > This is essentially the situation we have right now.  Judgement of
> > local mappers is usually fine (with the exception of political
> > cases like the Rio de la Plata).  Most problems occur because
> > armchair mappers misinterpret the local situation or when
> > inexperienced mappers are unaware of the significance of
> > distinguishing between ocean and riverbank mapping.
>
> What guidance do we give to the local mappers?

What is currently written on the wiki which includes the proposal which 
is linked to from the coastline documentation.

> Given a properly formulated rule-of-thumb, why should remote armchair
> mappers come to a different conclusion to local mappers in this case?

As said this is mostly due to misinterpreting imagery.

-- 
Christoph Hormann
http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

On 2018-09-03 22:20, Christoph Hormann wrote:

>> The estuarine situation will always be hard to deal with, and I think
>> we'll simply need to have rough guidelines and then trust the
>> judgment of the locals.
> 
> This is essentially the situation we have right now.  Judgement of local 
> mappers is usually fine (with the exception of political cases like the 
> Rio de la Plata).  Most problems occur because armchair mappers 
> misinterpret the local situation or when inexperienced mappers are 
> unaware of the significance of distinguishing between ocean and 
> riverbank mapping.

What guidance do we give to the local mappers? Coastline up to tidal
limit, or draw a line across wherever you think fit? Coastline and
riverbank are IMHO not mutually exclusive. 

Given a properly formulated rule-of-thumb, why should remote armchair
mappers come to a different conclusion to local mappers in this case? Or
are you proposing such a wide tolerance that basically anything will
fit, thus avoiding the discussion instead of actually tackling it?___
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Colin Smale]

Just a reminder that we need a pragmatic, practical definition for OSM.
It has to be either verifiable in situ, preferably in a single visit and
without specialist equipment, knowledge or access, or it needs to be
derivable from openly accessible (and suitably licensed) sources. A
discussion whereby a hundred people contribute their subjective opinions
is unlikely to lead to a *durable* solution for OSM. In this case I
would suggest it would be impossible for a mapper to survey their own
coastline position; it is best left to hydrographers and/or
cartographers to provide the algorithm by which one can define the
correct "coastline". Then we find an open source of this data for our
regions. If this source does not exist, we approximate (based on the
chosen algorithm) until such time as open data is available. 

The nicest thing about standards is of course the wide choice
available Which standard do we adopt? Is it not possible that there
are multiple possibilities for the definition of "coastline", and which
one is best for a given use case, can vary according to the wishes of
the party consuming the data? I.e. if we preselect a specific
definition, are we implicitly and unintentionally blocking out other
definitions from representation in OSM, possibly leading to accusations
of "tagging for the renderer," being the single use case which uses the
chosen definition? 

One thing I think does have consensus - the coastline is based on the
High Water Mark (and not Low Water or mid-tide or any other point in the
tidal cycle). This in itself is impossible for a "simple mapper" to
define with any accuracy, so we will have to trust external sources. 

What is unclear, is of course where do we "draw the line", literally and
figuratively, in the case of indented coastlines and river estuaries.
Tidal limit has the advantage of being artificial (dam/weir etc) and
therefore uncontroversial, or at least in most cases readily available,
even if it is just from "common knowledge". So which standard/algorithm
would give the pragmatic, practical definition OSM needs?

On 2018-09-03 21:32, Kevin Kenny wrote:

> It would certainly need to be above Haverstraw - the current there
> http://tbone.biol.sc.edu/tide/tideshow.cgi?site=Haverstraw+%28Hudson+River%29%2C+New+York+Current
> shows significant tidal reversal.  I haven't found a gaging station
> farther upriver that reports tidal currents. Croton Point, where the
> river broadens to form the Tappan Zee, would probably be the lower
> limit. Even that seems unreasonably far upriver.
> 
> The tidal range increases as you move upstream from there. The
> greatest tidal range in the entire river is at Troy. One Native
> American name for the river was "Mahicantuck" which means, more or
> less, "the river flows both ways."
> 
> The estuarine situation will always be hard to deal with, and I think
> we'll simply need to have rough guidelines and then trust the judgment
> of the locals.
> On Mon, Sep 3, 2018 at 2:51 PM Christoph Hormann  wrote: 
> On Monday 03 September 2018, Kevin Kenny wrote: Imagico's proposal is perhaps 
> objective, but surely doesn't match
> perception in my part of the world. It seems odd that the 'coastline'
> must extend upward to https://www.openstreetmap.org/way/90929525 -
> but that is, according to Imagico's definitions, simultaneously the
> lowest and highest permissible limit. [...] 
> Then you have misunderstood the proposal.
> 
> With the Hudson river obviously the tidal case applies so you have the
> lower limit as:
> 
> With significant tides the coastline should go upstream at least to a
> point where on waterflow is going downstream for a significantly longer
> part of the tidal cycle than it goes upstream due to raising tide.
> 
> This is evidently always below the upper limit (range of tidal
> influence).
> 
> I can't say for sure where i would place the lower limit in case of the
> Hudson - The Narrows is quite definitely too low - but the current
> closure seems fine.
> 
> For low volume tidal rivers (i.e. without a salt wedge and no
> significant influence of the water volume on the ocean salinity) it
> would also be possible to define the lower limit through salinity (not
> in absolute terms but as a fraction of the open ocean salinity in the
> area).
> 
> --
> Christoph Hormann
> http://www.imagico.de/
> 
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Monday 03 September 2018, Kevin Kenny wrote:
> It would certainly need to be above Haverstraw - the current there
> http://tbone.biol.sc.edu/tide/tideshow.cgi?site=Haverstraw+%28Hudson+
>River%29%2C+New+York+Current shows significant tidal reversal.  I
> haven't found a gaging station farther upriver that reports tidal
> currents. Croton Point, where the river broadens to form the Tappan
> Zee, would probably be the lower limit. Even that seems unreasonably
> far upriver.
>
> The tidal range increases as you move upstream from there. The
> greatest tidal range in the entire river is at Troy. One Native
> American name for the river was "Mahicantuck" which means, more or
> less, "the river flows both ways."

I am not familiar with the specific situation but tidal reversal is not 
incompatible with the rule i formulated.

And as said for low volume tidal rivers a relative salinity criterion 
might work better - but this does not work with larger volume rivers 
where this could put the lower limit pretty far out into the ocean.

> The estuarine situation will always be hard to deal with, and I think
> we'll simply need to have rough guidelines and then trust the
> judgment of the locals.

This is essentially the situation we have right now.  Judgement of local 
mappers is usually fine (with the exception of political cases like the 
Rio de la Plata).  Most problems occur because armchair mappers 
misinterpret the local situation or when inexperienced mappers are 
unaware of the significance of distinguishing between ocean and 
riverbank mapping.

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http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Kevin Kenny]

It would certainly need to be above Haverstraw - the current there
http://tbone.biol.sc.edu/tide/tideshow.cgi?site=Haverstraw+%28Hudson+River%29%2C+New+York+Current
shows significant tidal reversal.  I haven't found a gaging station
farther upriver that reports tidal currents. Croton Point, where the
river broadens to form the Tappan Zee, would probably be the lower
limit. Even that seems unreasonably far upriver.

The tidal range increases as you move upstream from there. The
greatest tidal range in the entire river is at Troy. One Native
American name for the river was "Mahicantuck" which means, more or
less, "the river flows both ways."

The estuarine situation will always be hard to deal with, and I think
we'll simply need to have rough guidelines and then trust the judgment
of the locals.
On Mon, Sep 3, 2018 at 2:51 PM Christoph Hormann  wrote:
>
> On Monday 03 September 2018, Kevin Kenny wrote:
> > Imagico's proposal is perhaps objective, but surely doesn't match
> > perception in my part of the world. It seems odd that the 'coastline'
> > must extend upward to https://www.openstreetmap.org/way/90929525 -
> > but that is, according to Imagico's definitions, simultaneously the
> > lowest and highest permissible limit. [...]
>
> Then you have misunderstood the proposal.
>
> With the Hudson river obviously the tidal case applies so you have the
> lower limit as:
>
> With significant tides the coastline should go upstream at least to a
> point where on waterflow is going downstream for a significantly longer
> part of the tidal cycle than it goes upstream due to raising tide.
>
> This is evidently always below the upper limit (range of tidal
> influence).
>
> I can't say for sure where i would place the lower limit in case of the
> Hudson - The Narrows is quite definitely too low - but the current
> closure seems fine.
>
> For low volume tidal rivers (i.e. without a salt wedge and no
> significant influence of the water volume on the ocean salinity) it
> would also be possible to define the lower limit through salinity (not
> in absolute terms but as a fraction of the open ocean salinity in the
> area).
>
> --
> Christoph Hormann
> http://www.imagico.de/
>
> ___
> Tagging mailing list
> Tagging@openstreetmap.org
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Malcolm Herring]

On 03/09/2018 19:24, Paul Allen wrote:

I expect somebody has a better definition.


Just to muddy the waters (pun intended!):

In its catalogue of chartable objects for electronic charts, the IHO 
originally defined "coastline", "river bank", "canal bank" and "lake 
shore". However, when it came to the implementation, they abandoned 
these distinctions and mapped everything as "coastline"



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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Monday 03 September 2018, Kevin Kenny wrote:
> Imagico's proposal is perhaps objective, but surely doesn't match
> perception in my part of the world. It seems odd that the 'coastline'
> must extend upward to https://www.openstreetmap.org/way/90929525 -
> but that is, according to Imagico's definitions, simultaneously the
> lowest and highest permissible limit. [...]

Then you have misunderstood the proposal.

With the Hudson river obviously the tidal case applies so you have the 
lower limit as:

With significant tides the coastline should go upstream at least to a 
point where on waterflow is going downstream for a significantly longer 
part of the tidal cycle than it goes upstream due to raising tide. 

This is evidently always below the upper limit (range of tidal 
influence).

I can't say for sure where i would place the lower limit in case of the 
Hudson - The Narrows is quite definitely too low - but the current 
closure seems fine.

For low volume tidal rivers (i.e. without a salt wedge and no 
significant influence of the water volume on the ocean salinity) it 
would also be possible to define the lower limit through salinity (not 
in absolute terms but as a fraction of the open ocean salinity in the 
area).

-- 
Christoph Hormann
http://www.imagico.de/

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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Paul Allen]

On Mon, Sep 3, 2018 at 7:08 PM, Kevin Kenny  wrote:

 it reasonable to draw 'coastline' on fresh water?


There is going to be diffusion, although that will be dwarfed by tidal
effects.  And since ocean salinity comes from rivers
washing salt out of the soil to the sea, careful measurements will find
salinity far upstream.

Not being a hydrologer, or a professional cartographer I would have thought
tides had a part to play.  I.e., where a river's
high water mark fluctuates (roughly) twice daily or where flow is reversed
in an estuary because of tidal flow.

I expect somebody has a better definition.

-- 
Paul
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Kevin Kenny]

Imagico's proposal is perhaps objective, but surely doesn't match
perception in my part of the world. It seems odd that the 'coastline'
must extend upward to https://www.openstreetmap.org/way/90929525 - but
that is, according to Imagico's definitions, simultaneously the lowest
and highest permissible limit. The locals would be astonished to call
the whole lower Hudson River 'ocean,' even though it is tidal.
Salinity varies; the point at which chloride concentration of 100 mg/l
is observed varies seasonally by over 100 km. There is an observable
salinity gradient through the entire estuary, but anywhere north of,
say, Hyde Park is 'fresh' water by any reasonable definition, even in
a dry summer. Is it reasonable to draw 'coastline' on fresh water?
On Mon, Sep 3, 2018 at 12:05 PM Christoph Hormann  wrote:
>
> On Monday 03 September 2018, Joseph Eisenberg wrote:
> > In my case, I've been debating whether to change the tagging of the
> > coastline in southwestern New Guinea (Papua, Indonesia) where many
> > large tropical rivers meet the Arafura sea among mangroves. The heavy
> > rainfall in this area means that the rivers have a pronounced
> > current. But the water is brackish and certainly tidally-influenced
> > far inland. Right now, it seems odd that many patches of mangroves
> > are made into "islands" by the use of natural=coastline, though
> > locally they would be considered part of the larger landmass of New
> > Guinea.
>
> The sitaution at a mangrove coast is slightly different from elsewhere
> because the mangrove forest is typically mapped as land w.r.t. the
> coastline which makes the tidal channels in between look like wide
> rivers - which is however often misleading.
>
> For example
>
> https://www.openstreetmap.org/relation/3111444
>
> is not a river despite being tagged as a riverbank polygon.
>
> This misunderstanding of the nature of mangrove coasts misinterpreting
> wide tidal channels as large rivers has led for example for some time
> in West Africa to a massive shortening of the coastline and a large
> fraction of virtual closing segments in the total coastline lenth -
> see:
>
> http://www.imagico.de/map/coastline_quality4_en.php
>
> This is now mostly fixed but the lure especially of armchair mappers to
> map this way is still there.
>
> > See: https://www.openstreetmap.org/#map=11/-4.8806/136.9339 ; the
> > coastline is quite noticable because it has also been tagged as the
> > administrative boundary.
>
> The administrative boundaries are generally a bad place to position the
> coastline because they are typically defined very differently from how
> OSM defines the coastline (and are also mostly very inaccurate
> geometrically).
>
> > What will be most helpful for data users and map renderers? Should
> > the coastline extend inland many kilometers, to where the mangroves
> > end? This will create a large number of apparent islands, and small
> > rivers will be entirely part of the "ocean" beyond the coastline.
> > Should it be down the the mouth of the river, to keep the coastline
> > as compact as possible?
>
> The coastline should be (a) a meaningful geometry on its own, i.e. the
> virtual parts of it (closing segments at river mouths) should be short
> and (b) be as easy to verify for the mapper as possible.
>
> Technically it is also important that the range of acceptable coastline
> positions is not too large so mappers do not move around the coastline
> a lot just to scratch their personal itch.
>
> > What about huge estuaries like the Saint Lawrence and the Rio De La
> > Plata? Should there be a vote on Imagico's proposal, or a new
> > proposal?
>
> I would be glad if anyone wants to reactivate the proposal or comes up
> with simpler rules for where to close the coastline.  But IMO a hard
> requirement for this would be that these are physically based rules
> rooted in the observable reality and not based on political or other
> purely abstract considerations.
>
> Some newer examples of problematic closure placements (in addition to
> the ones in the proposal):
>
> https://www.openstreetmap.org/way/463191729
> https://www.openstreetmap.org/way/474230093
>
> --
> Christoph Hormann
> http://www.imagico.de/
>
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Re: [Tagging] Coastline for rivers, estuaries and mangroves?

[Christoph Hormann]

On Monday 03 September 2018, Joseph Eisenberg wrote:
> In my case, I've been debating whether to change the tagging of the
> coastline in southwestern New Guinea (Papua, Indonesia) where many
> large tropical rivers meet the Arafura sea among mangroves. The heavy
> rainfall in this area means that the rivers have a pronounced
> current. But the water is brackish and certainly tidally-influenced
> far inland. Right now, it seems odd that many patches of mangroves
> are made into "islands" by the use of natural=coastline, though
> locally they would be considered part of the larger landmass of New
> Guinea.

The sitaution at a mangrove coast is slightly different from elsewhere 
because the mangrove forest is typically mapped as land w.r.t. the 
coastline which makes the tidal channels in between look like wide 
rivers - which is however often misleading.

For example

https://www.openstreetmap.org/relation/3111444

is not a river despite being tagged as a riverbank polygon.

This misunderstanding of the nature of mangrove coasts misinterpreting 
wide tidal channels as large rivers has led for example for some time 
in West Africa to a massive shortening of the coastline and a large 
fraction of virtual closing segments in the total coastline lenth - 
see:

http://www.imagico.de/map/coastline_quality4_en.php

This is now mostly fixed but the lure especially of armchair mappers to 
map this way is still there.

> See: https://www.openstreetmap.org/#map=11/-4.8806/136.9339 ; the
> coastline is quite noticable because it has also been tagged as the
> administrative boundary.

The administrative boundaries are generally a bad place to position the 
coastline because they are typically defined very differently from how 
OSM defines the coastline (and are also mostly very inaccurate 
geometrically).

> What will be most helpful for data users and map renderers? Should
> the coastline extend inland many kilometers, to where the mangroves
> end? This will create a large number of apparent islands, and small
> rivers will be entirely part of the "ocean" beyond the coastline.
> Should it be down the the mouth of the river, to keep the coastline
> as compact as possible?

The coastline should be (a) a meaningful geometry on its own, i.e. the 
virtual parts of it (closing segments at river mouths) should be short 
and (b) be as easy to verify for the mapper as possible.

Technically it is also important that the range of acceptable coastline 
positions is not too large so mappers do not move around the coastline 
a lot just to scratch their personal itch.

> What about huge estuaries like the Saint Lawrence and the Rio De La
> Plata? Should there be a vote on Imagico's proposal, or a new
> proposal?

I would be glad if anyone wants to reactivate the proposal or comes up 
with simpler rules for where to close the coastline.  But IMO a hard 
requirement for this would be that these are physically based rules 
rooted in the observable reality and not based on political or other 
purely abstract considerations.

Some newer examples of problematic closure placements (in addition to 
the ones in the proposal):

https://www.openstreetmap.org/way/463191729
https://www.openstreetmap.org/way/474230093

-- 
Christoph Hormann
http://www.imagico.de/

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[Tagging] Coastline for rivers, estuaries and mangroves?

[Joseph Eisenberg]

I recently searched for clear guidance about where a river estuary should
be tagged with natural=coastline rather than water=river or riverbank.
While I found Imagico's proposal (
https://wiki.openstreetmap.org/wiki/Talk:Proposed_Features/Coastline-River_transit_placement),
it seems that it was not brought to a vote, and there was some controversy.
(
https://wiki.openstreetmap.org/wiki/Talk:Proposed_Features/Coastline-River_transit_placement
).

Recently another user was concered by the apperance of a waterway=river
within natural=coastline, and asked about this, but we don't have a clear
answer:
https://help.openstreetmap.org/questions/65629/should-riverbanks-be-tagged-as-naturalcoastline

In my case, I've been debating whether to change the tagging of the
coastline in southwestern New Guinea (Papua, Indonesia) where many large
tropical rivers meet the Arafura sea among mangroves. The heavy rainfall in
this area means that the rivers have a pronounced current. But the water is
brackish and certainly tidally-influenced far inland. Right now, it seems
odd that many patches of mangroves are made into "islands" by the use of
natural=coastline, though locally they would be considered part of the
larger landmass of New Guinea.

See: https://www.openstreetmap.org/#map=11/-4.8806/136.9339 ; the coastline
is quite noticable because it has also been tagged as the administrative
boundary.

What will be most helpful for data users and map renderers? Should the
coastline extend inland many kilometers, to where the mangroves end? This
will create a large number of apparent islands, and small rivers will be
entirely part of the "ocean" beyond the coastline. Should it be down the
the mouth of the river, to keep the coastline as compact as possible?

What about huge estuaries like the Saint Lawrence and the Rio De La Plata?
Should there be a vote on Imagico's proposal, or a new proposal?
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