Re: [Talk-GB] Coastline and tidal rivers

[Colin Smale]

On 2018-09-02 10:50, Warin wrote:

> On 29/08/18 01:46, Colin Smale wrote: 
> 
> On 2018-08-28 16:43, David Groom wrote: 
> whilst in theory I'd say yes, in practice I'd say consensus is hard to 
> achieve. 
> OK, I might as well give up now then. If everybody started thinking "I don't 
> know why I bother," like I am now, where would we be?

To Colin I say in a loud voice ... "Up the Rebels" :) 

Thanks for the support...

> On the Australian talk list this came up for an import or maritime boundaries 
> -note the last bits 
> 
> _Geoscience Australia definitions:_
> 
> * _"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."_ 
> 
> Probably this same distinction exists in the UK - that difference of internal 
> waters for international law. This may help achieve a 'consensus'?

The baseline is not the same as the coastline. 

The Coastline is: 

* A geographic concept delimiting the dry bit from the damp and wet
bits
* Based on high water mark

The Baseline is: 

* A legal concept, used as the basis for jurisdiction over territorial
waters etc
* Based on low water mark, with international rules for handling bays,
coastal islands, inlets etc

What you are referencing in Australia is the Baseline and it certainly
exists in the UK, but AFAIK it is not represented directly in OSM. The
12nm territorial waters limit which should be derived from the baseline
is however present in OSM. 

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Links:
--
[1]
http://www.ga.gov.au/scientific-topics/marine/jurisdiction/maritime-boundaries___
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Re: [Talk-GB] Coastline and tidal rivers

[Warin]

On 29/08/18 01:46, Colin Smale wrote:


On 2018-08-28 16:43, David Groom wrote:

whilst in theory I'd say yes, in practice I'd say consensus is hard 
to achieve.
OK, I might as well give up now then. If everybody started thinking "I 
don't know why I bother," like I am now, where would we be?


To Colin I say in a loud voice ... "Up the Rebels" :)

On the Australian talk list this came up for an import or maritime 
boundaries -note the last bits


/Geoscience Australia definitions:/
/
/

 * /"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."/


Probably this same distinction exists in the UK - that difference of 
internal waters for international law. This may help achieve a 'consensus'?


/
/

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Re: [Talk-GB] Coastline and tidal rivers

[Mike Evans]

Hi David

On Wed, 29 Aug 2018 09:09:58 +
"David Groom"  wrote:

 
> >>There is no consensus.
> >>
> >>Personally I'm not in favour of the view that any body of water which 
> >>is
> >>tidal should be bounded by a way tagged as coastline.
> >>
> >>Reasons for this
> >>
> >>1) Ask any one who lives in say central London "do you live on the
> >>coast" or do you live beside a river", most would I'm sure say beside 
> >>a
> >>river, so surely our data should reflect that. I think this probably 
> >>is
> >>what you mean by "seems more natural"  
> >Well if they're in Central London then it is an estuary at that point 
> >so they'd be incorrect. Hence the expression "estuary English", and not 
> >"river English".  
> Both the Oxford and Cambridge Dictionaries define as estuary as part of 
> a river.

Dictionaries are written for writers and are not necessarily useful as a 
mapping resource.
There's more here: https://en.wikipedia.org/wiki/Thames_Estuary


> >
> >Perhaps "A History of the Foreshore and the Law Relating Thereto", 
> >published 1888 would be a useful reference.
> >https://archive.org/details/ahistoryforesho00hallgoog
> >
> >  
> >>
> >>2) In part because the converse is not true, we bound large non tidal
> >>water areas as coastline  
> >Examples?
> >  
> Baltic , Caspian & Black Seas
>
All are tidal to small extent, see:
https://www.frontiersin.org/articles/10.3389/fmars.2016.00046/full

But none of this helps us draw an arbitrary line across a 
river/estuary/tidal/non-tidal water body.

Regards Mike 

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Re: [Talk-GB] Coastline and tidal rivers

[David Groom]

-- Original Message --
From: "Mike Evans" 
To: talk-gb@openstreetmap.org
Cc: "David Groom" 
Sent: 28/08/2018 19:22:16
Subject: Re: [Talk-GB] Coastline and tidal rivers


On Tue, 28 Aug 2018 11:09:47 +
"David Groom"  wrote:


There is no consensus.

Personally I'm not in favour of the view that any body of water which 
is

tidal should be bounded by a way tagged as coastline.

Reasons for this

1) Ask any one who lives in say central London "do you live on the
coast" or do you live beside a river", most would I'm sure say beside 
a
river, so surely our data should reflect that. I think this probably 
is

what you mean by "seems more natural"
Well if they're in Central London then it is an estuary at that point 
so they'd be incorrect. Hence the expression "estuary English", and not 
"river English".
Both the Oxford and Cambridge Dictionaries define as estuary as part of 
a river.




To quote Wikpedia "The district of Teddington a few miles south-west of 
London's centre marks the boundary between the tidal and non-tidal 
parts of the Thames".
The Wikipedia quote to which you refer suggests to  me that this should 
be tagged as a river, since the Thames is a river, parts of which are 
tidal and parts of which are not.  But it's still a river.





Perhaps "A History of the Foreshore and the Law Relating Thereto", 
published 1888 would be a useful reference.

https://archive.org/details/ahistoryforesho00hallgoog




2) In part because the converse is not true, we bound large non tidal
water areas as coastline

Examples?


Baltic , Caspian & Black Seas





3) If knowledge that a body of water is tidal is important it can be
tagged "tidal = yes"
But then the decision has to made as to where to draw the line and tag 
one side as "tidal = yes" and the other side not tagged but assumed to, 
in fact, be tidal. This just introduces an extra arbitrary boundary the 
inner end of which again becomes non-tidal.


The American Submerged Lands Act of 1953 does appear to define the line 
at which the coastline extends into estuaries etc., but this does not 
apply to the UK. That act seems to been precipitated as a result of 
disputes over oil drilling rights.


Mike
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Re: [Talk-GB] Coastline and tidal rivers

[Mike Evans]

On Tue, 28 Aug 2018 11:09:47 +
"David Groom"  wrote:

> There is no consensus.
> 
> Personally I'm not in favour of the view that any body of water which is 
> tidal should be bounded by a way tagged as coastline.
> 
> Reasons for this
> 
> 1) Ask any one who lives in say central London "do you live on the 
> coast" or do you live beside a river", most would I'm sure say beside a 
> river, so surely our data should reflect that.  I think this probably is 
> what you mean by "seems more natural"
Well if they're in Central London then it is an estuary at that point so they'd 
be incorrect. Hence the expression "estuary English", and not "river English".
To quote Wikpedia "The district of Teddington a few miles south-west of 
London's centre marks the boundary between the tidal and non-tidal parts of the 
Thames". 

Perhaps "A History of the Foreshore and the Law Relating Thereto",  published 
1888 would be a useful reference.
https://archive.org/details/ahistoryforesho00hallgoog


> 
> 2)  In part because the converse is not true, we bound large non tidal 
> water areas as coastline
Examples?

> 
> 3) If knowledge that a body of water is tidal is important it can be 
> tagged "tidal = yes"
But then the decision has to made as to where to draw the line and tag one side 
as "tidal = yes" and the other side not tagged but assumed to, in fact, be 
tidal. This just introduces an extra arbitrary boundary the inner end of which 
again becomes non-tidal.

The American Submerged Lands Act of 1953 does appear to define the line at 
which the coastline extends into estuaries etc., but this does not apply to the 
UK.  That act seems to been precipitated as a result of disputes over oil 
drilling rights.

Mike


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Re: [Talk-GB] Coastline and tidal rivers

[Colin Smale]

On 2018-08-28 16:43, David Groom wrote:

> whilst in theory I'd say yes, in practice I'd say consensus is hard to 
> achieve.

OK, I might as well give up now then. If everybody started thinking "I
don't know why I bother," like I am now, where would we be?___
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Re: [Talk-GB] Coastline and tidal rivers

[David Groom]

Colin

whilst in theory I'd say yes, in practice I'd say consensus is hard to 
achieve.


David



-- Original Message --
From: "Colin Smale" 
To: talk-gb@openstreetmap.org
Sent: 28/08/2018 12:23:33
Subject: Re: [Talk-GB] Coastline and tidal rivers

David, do you consider that it would be advantageous to have consensus 
on this matter, and a consistent tagging paradigm in OSM? I am not 
prejudging what that consensus position might be, just sounding out if 
there is any point in having the discussion in the first place.





On 2018-08-28 13:09, David Groom wrote:


There is no consensus.

Personally I'm not in favour of the view that any body of water which 
is tidal should be bounded by a way tagged as coastline.


Reasons for this

1) Ask any one who lives in say central London "do you live on the 
coast" or do you live beside a river", most would I'm sure say beside 
a river, so surely our data should reflect that.  I think this 
probably is what you mean by "seems more natural"


2)  In part because the converse is not true, we bound large non tidal 
water areas as coastline


3) If knowledge that a body of water is tidal is important it can be 
tagged "tidal = yes"



David




-- Original Message --
From: "Colin Smale" 
To: "Talk-GB" 
Sent: 28/08/2018 08:49:01
Subject: [Talk-GB] Coastline and tidal rivers

That old chestnut again...

There seems to be an open discussion about how far up a river the 
natural=coastline should go. The wiki suggests the coastline should be 
the high water line going up to the tidal limit (often a lock or a 
wier) but this can be a substantial distance inland. This is AIUI the 
general scientific approach.


There has been some discussion in the past about letting the coastline 
cut across the river at some convenient point, possibly because it 
"looks better" or "seems more natural" or "is less work."


I looked at a few rivers along the south coast to see how they had 
been tagged and it seems most have the coastline up to the tidal 
limit. However the coastline around the mouth of the Dart has recently 
been modified to cut across the mouth, and Salcombe Harbour is also 
mapped this way.


Is there a consensus for a particular definition of "coastline" in 
tidal estuaries? Should we try to keep a consistent paradigm, or 
doesn't it matter?






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Re: [Talk-GB] Coastline and tidal rivers

[Colin Smale]

David, do you consider that it would be advantageous to have consensus
on this matter, and a consistent tagging paradigm in OSM? I am not
prejudging what that consensus position might be, just sounding out if
there is any point in having the discussion in the first place.

On 2018-08-28 13:09, David Groom wrote:

> There is no consensus. 
> 
> Personally I'm not in favour of the view that any body of water which is 
> tidal should be bounded by a way tagged as coastline.  
> 
> Reasons for this 
> 
> 1) Ask any one who lives in say central London "do you live on the coast" or 
> do you live beside a river", most would I'm sure say beside a river, so 
> surely our data should reflect that.  I think this probably is what you mean 
> by "seems more natural" 
> 
> 2)  In part because the converse is not true, we bound large non tidal water 
> areas as coastline 
> 
> 3) If knowledge that a body of water is tidal is important it can be tagged 
> "tidal = yes" 
> 
> David 
> 
> -- Original Message -- 
> From: "Colin Smale"  
> To: "Talk-GB"  
> Sent: 28/08/2018 08:49:01 
> Subject: [Talk-GB] Coastline and tidal rivers 
> 
> That old chestnut again... 
> 
> There seems to be an open discussion about how far up a river the 
> natural=coastline should go. The wiki suggests the coastline should be the 
> high water line going up to the tidal limit (often a lock or a wier) but this 
> can be a substantial distance inland. This is AIUI the general scientific 
> approach. 
> 
> There has been some discussion in the past about letting the coastline cut 
> across the river at some convenient point, possibly because it "looks better" 
> or "seems more natural" or "is less work." 
> 
> I looked at a few rivers along the south coast to see how they had been 
> tagged and it seems most have the coastline up to the tidal limit. However 
> the coastline around the mouth of the Dart has recently been modified to cut 
> across the mouth, and Salcombe Harbour is also mapped this way. 
> 
> Is there a consensus for a particular definition of "coastline" in tidal 
> estuaries? Should we try to keep a consistent paradigm, or doesn't it matter? 
> 
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Re: [Talk-GB] Coastline and tidal rivers

[David Groom]

There is no consensus.

Personally I'm not in favour of the view that any body of water which is 
tidal should be bounded by a way tagged as coastline.


Reasons for this

1) Ask any one who lives in say central London "do you live on the 
coast" or do you live beside a river", most would I'm sure say beside a 
river, so surely our data should reflect that.  I think this probably is 
what you mean by "seems more natural"


2)  In part because the converse is not true, we bound large non tidal 
water areas as coastline


3) If knowledge that a body of water is tidal is important it can be 
tagged "tidal = yes"



David




-- Original Message --
From: "Colin Smale" 
To: "Talk-GB" 
Sent: 28/08/2018 08:49:01
Subject: [Talk-GB] Coastline and tidal rivers

That old chestnut again...

There seems to be an open discussion about how far up a river the 
natural=coastline should go. The wiki suggests the coastline should be 
the high water line going up to the tidal limit (often a lock or a wier) 
but this can be a substantial distance inland. This is AIUI the general 
scientific approach.


There has been some discussion in the past about letting the coastline 
cut across the river at some convenient point, possibly because it 
"looks better" or "seems more natural" or "is less work."


I looked at a few rivers along the south coast to see how they had been 
tagged and it seems most have the coastline up to the tidal limit. 
However the coastline around the mouth of the Dart has recently been 
modified to cut across the mouth, and Salcombe Harbour is also mapped 
this way.


Is there a consensus for a particular definition of "coastline" in tidal 
estuaries? Should we try to keep a consistent paradigm, or doesn't it 
matter?



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Re: [Talk-GB] Coastline and tidal rivers

[Tony Shield]

I'm with Colin on this.

My experience of sailing and reading Admiralty charts is that the 
coastline is the High Water line.  Yes it looks inconvenient or 
unnatural - but tidal area as implied by coastline is so important to 
small boat users. The River Dart



   Way: 194211894 waterway= riverbank

is a really arbitrary line across the river from Dartmouth Castle, this 
offends my view of what a coastline is.


Another relevant concept is salinity - tidal coastline is saline and 
does affect plant and marine life . Which leads us into a conundrum - 
things such as salt marsh and mangrove swamps which are all inter-tidal; 
where should the coastline be?


We should also be aware that an incoming tide blocks the natural flow of 
the river and causes the river to form a type of lake which reduces as 
the tide ebbs. This effect can cause people to think a river is tidal in 
that area when it is not.


In my local area the River Ribble estuary in OSM changes from riverbank 
to coastline near Warton airfield, but wikipedia describes "The Normal 
Tidal Limit (NTL) of the river is at Fishwick Bottoms, between Preston 
andWalton-le-Dale , 11 
miles (18 km) from the sea"


so where should the boundary of coastline to  riverbank be? I suggest 
where the inter-tidal range or zonal area is small - range < 1 foot, 
line of zone perpendicular to the boundary is < 1 yard (or metric 
equivalent).
A heuristic could be where it becomes long and thin? Ribble is almost 
acceptable - Dart is not as I write this.


But really I prefer the existing guidance.

Regards
TonyS999


On 28/08/2018 08:49, Colin Smale wrote:


That old chestnut again...

There seems to be an open discussion about how far up a river the 
natural=coastline should go. The wiki suggests the coastline should be 
the high water line going up to the tidal limit (often a lock or a 
wier) but this can be a substantial distance inland. This is AIUI the 
general scientific approach.


There has been some discussion in the past about letting the coastline 
cut across the river at some convenient point, possibly because it 
"looks better" or "seems more natural" or "is less work."


I looked at a few rivers along the south coast to see how they had 
been tagged and it seems most have the coastline up to the tidal 
limit. However the coastline around the mouth of the Dart has recently 
been modified to cut across the mouth, and Salcombe Harbour is also 
mapped this way.


Is there a consensus for a particular definition of "coastline" in 
tidal estuaries? Should we try to keep a consistent paradigm, or 
doesn't it matter?





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