coastline v. water

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coastline v. water

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After a few days of much work, a recent collaborative project to turn the Chesapeake Bay from a nothing space outlined by natural=coastline to what we considered to be a more accurate relation of natural=water, we've received some negative feedback.

The difference of opinion seems to lie in the definition of what we're mapping.  The use of coastline is for "seas"[0] while the use of water is for "inland areas of water"[1].  Even though the Chesapeake Bay is tidal, there is no question that it is an inland waterway (it is completely surrounded by land except for the mouth at its southeast side).  The idea of using coastlines for basically creating an edge between the land and the nothingness of the ocean makes sense when, as far as the eye can see it's only water.

Now, some of the feedback that has been presented[2] is that because it is tidal it is part of the sea.  I have pointed out that many rivers and streams (and ditches!) are tidal; does that make them part of the sea?  I would not think so.  In fact, there are named seas on this planet that are not even connected to other water formations (the tiniest, according to the National Geographic, is the Sea of Marmara which has an area just less than 12,950 sq km, larger than the Chesapeake Bay).

But, tagging the Chesapeake Bay, and its tributaries, as "water" brings several benefits to the map and the users.  First, it helps identify the sections of water that exist in these areas (this can't really be done with node points as there is no way to define start and end points of an area).  There are many defined bays, rivers, and streams that make up the greater Chesapeake Bay area.  What one may see as one large mass of water is actually many smaller defined segments each with their own history.  Second, we can speed up any updates (fixes) to outlines of the polygons that happen in these water areas without having to wait for the entire Earth's coastlines to be re-rendered.  I suspect having less coastline to render would also speed up the rendering of coastlines as well?

I would like for the tagging community to clarify the different between "water" and "coastline" and when to use each.  The definition on water seems to say to use it on inland water but there seems to be, at least, and open interpretation of the word "sea" for coastline that is dragging many inland waters into that category.

Thanks,
Eric "Sparks" Christensen

[0] https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline
[1] https://wiki.openstreetmap.org/wiki/Tag:natural%3Dwater
[2] https://www.openstreetmap.org/changeset/94093155#map=10/37.1620/-76.1581

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Re: coastline v. water

Joseph Eisenberg
Chesapeake Bay, as the name “Bay” suggests, is a bay at the edge of the Atlantic Ocean. It is a shallow estuary, similar to many othe partially enclosed margins seas, e.g. the Salish Sea (including Puget Sound) in Washington/British Columbia, San Francisco Bay in California, the Tampa Bay in Florida, etc.

It has always been the standard to map these bays as part of the marine environment by using the natural=coastline to include them as part of the marginal sea.

Consider that the natural=coastline is defined as representing the mean high water springs line, that is, the line of the highest tides. If the line on an open ocean beach is at the high tide line, it makes sense that all tidal bays and estuaries should also be included in the area outside of the coastline.

While there is some debate about where on the Potomac River we should put the line (I would suggest around DC, where the river widens out), there is no doubt that Chesapeake Bay is part of the marine environment.

— Joseph Eisenberg

On Wed, Nov 18, 2020 at 12:24 PM Eric H. Christensen via Tagging <[hidden email]> wrote:
After a few days of much work, a recent collaborative project to turn the Chesapeake Bay from a nothing space outlined by natural=coastline to what we considered to be a more accurate relation of natural=water, we've received some negative feedback.

The difference of opinion seems to lie in the definition of what we're mapping.  The use of coastline is for "seas"[0] while the use of water is for "inland areas of water"[1].  Even though the Chesapeake Bay is tidal, there is no question that it is an inland waterway (it is completely surrounded by land except for the mouth at its southeast side).  The idea of using coastlines for basically creating an edge between the land and the nothingness of the ocean makes sense when, as far as the eye can see it's only water.

Now, some of the feedback that has been presented[2] is that because it is tidal it is part of the sea.  I have pointed out that many rivers and streams (and ditches!) are tidal; does that make them part of the sea?  I would not think so.  In fact, there are named seas on this planet that are not even connected to other water formations (the tiniest, according to the National Geographic, is the Sea of Marmara which has an area just less than 12,950 sq km, larger than the Chesapeake Bay).

But, tagging the Chesapeake Bay, and its tributaries, as "water" brings several benefits to the map and the users.  First, it helps identify the sections of water that exist in these areas (this can't really be done with node points as there is no way to define start and end points of an area).  There are many defined bays, rivers, and streams that make up the greater Chesapeake Bay area.  What one may see as one large mass of water is actually many smaller defined segments each with their own history.  Second, we can speed up any updates (fixes) to outlines of the polygons that happen in these water areas without having to wait for the entire Earth's coastlines to be re-rendered.  I suspect having less coastline to render would also speed up the rendering of coastlines as well?

I would like for the tagging community to clarify the different between "water" and "coastline" and when to use each.  The definition on water seems to say to use it on inland water but there seems to be, at least, and open interpretation of the word "sea" for coastline that is dragging many inland waters into that category.

Thanks,
Eric "Sparks" Christensen

[0] https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline
[1] https://wiki.openstreetmap.org/wiki/Tag:natural%3Dwater
[2] https://www.openstreetmap.org/changeset/94093155#map=10/37.1620/-76.1581

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Re: coastline v. water

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, November 18th, 2020 at 3:31 PM, Joseph Eisenberg <[hidden email]> wrote:

> Consider that the natural=coastline is defined as representing the mean high water springs line, that is, the line of the highest tides. If the line on an open ocean beach is at the high tide line, it makes sense that all tidal bays and estuaries should also be included in the area outside of the coastline.

Then why the ability to mark natural=water as tidal and as salt?  Clearly the ability to use those attributes leads me to believe that just being tidal does not make it be coastline.

--Eric

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Re: coastline v. water

Colin Smale
In reply to this post by Joseph Eisenberg

On 2020-11-18 21:31, Joseph Eisenberg wrote:

Consider that the natural=coastline is defined as representing the mean high water springs line, that is, the line of the highest tides.
 
Sorry to pick nits, but tides can be higher than MHWS; the "mean" implies a long-term average, which will often be exceeded.
 

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Re: coastline v. water

Christoph Hormann-2
In reply to this post by Tagging mailing list
> Eric H. Christensen via Tagging <[hidden email]> hat am 18.11.2020 21:19 geschrieben:
>
> [...]

First: the matter has been discussed at length previously so i would advise anyone who wants to form an opinion on the matter to read up on past discussion where essentially everything relevant has been said already.  Most relevant links:

https://lists.openstreetmap.org/pipermail/tagging/2020-July/054405.html
and resulting discussion:
https://lists.openstreetmap.org/pipermail/tagging/2020-August/thread.html#54434

https://wiki.openstreetmap.org/wiki/Proposed_Features/Coastline-River_transit_placement

Second:

>
> Now, some of the feedback that has been presented[2] is that because it is tidal it is part of the sea.  [...]

As you can read in the proposal linked above the range of tidal influence forms the upper limit of the range practical coastline mapping in areas with significant tidal range but as it is in practical mapping not the universally used limit.

Third:

While this is ultimately not relevant because the delineation of tags in OSM should be based on verifiable criteria obviously i have never seen any map that displays ocean water and inland waterbodies in differentiated form that shows the Chesapeake Bay as inland water.

Classical examples with differentiated rendering are TPC/ONC (caution: links go to large images):

http://legacy.lib.utexas.edu/maps/tpc/americas-pacific-index.html
http://legacy.lib.utexas.edu/maps/onc/txu-pclmaps-oclc-8322829_g_21.jpg

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

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Re: coastline v. water

Brian M. Sperlongano
This was fascinating reading.  I do agree that we ought to have a definition for what gets tagged natural=coastline, and I think it's fine if that definition has some subjectivity.

I would offer something as simple as:

"The coastline should follow the mean high tide line.  In some cases this rule would result in the coastline extending an unreasonable distance along the banks of tidal rivers.  In those cases, mappers should identify a reasonable choke point at which to terminate the inland extent of coastline tagging."

This would clearly include bays and coves on the marine side of the coast.  For rivers, local mappers could decide on where the coastline stops by consensus, and the decision space is limited to a discrete set of chokepoints in the river geography (or when the river stops being tidal if the tidal portion is reasonably short).

An objective definition that we can all live with is probably not achievable, but a partially-subjective one would at least minimize the arbitrary decision-making while still allowing flexibility for edge cases.


On Wed, Nov 18, 2020 at 5:07 PM Christoph Hormann <[hidden email]> wrote:
> Eric H. Christensen via Tagging <[hidden email]> hat am 18.11.2020 21:19 geschrieben:
>
> [...]

First: the matter has been discussed at length previously so i would advise anyone who wants to form an opinion on the matter to read up on past discussion where essentially everything relevant has been said already.  Most relevant links:

https://lists.openstreetmap.org/pipermail/tagging/2020-July/054405.html
and resulting discussion:
https://lists.openstreetmap.org/pipermail/tagging/2020-August/thread.html#54434

https://wiki.openstreetmap.org/wiki/Proposed_Features/Coastline-River_transit_placement

Second:

>
> Now, some of the feedback that has been presented[2] is that because it is tidal it is part of the sea.  [...]

As you can read in the proposal linked above the range of tidal influence forms the upper limit of the range practical coastline mapping in areas with significant tidal range but as it is in practical mapping not the universally used limit.

Third:

While this is ultimately not relevant because the delineation of tags in OSM should be based on verifiable criteria obviously i have never seen any map that displays ocean water and inland waterbodies in differentiated form that shows the Chesapeake Bay as inland water.

Classical examples with differentiated rendering are TPC/ONC (caution: links go to large images):

http://legacy.lib.utexas.edu/maps/tpc/americas-pacific-index.html
http://legacy.lib.utexas.edu/maps/onc/txu-pclmaps-oclc-8322829_g_21.jpg

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

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Re: coastline v. water

Tagging mailing list
In reply to this post by Christoph Hormann-2
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, November 18th, 2020 at 5:04 PM, Christoph Hormann <[hidden email]> wrote:

> > Eric H. Christensen via Tagging [hidden email] hat am 18.11.2020 21:19 geschrieben:
>
> > [...]
>
> First: the matter has been discussed at length previously so i would advise anyone who wants to form an opinion on the matter to read up on past discussion where essentially everything relevant has been said already. Most relevant links:
>
> https://lists.openstreetmap.org/pipermail/tagging/2020-July/054405.html
>
> and resulting discussion:
>
> https://lists.openstreetmap.org/pipermail/tagging/2020-August/thread.html#54434
>
> https://wiki.openstreetmap.org/wiki/Proposed_Features/Coastline-River_transit_placement

Whew, after reading all of those messages, my take-away is that it's mostly what the locals see the water as.

> Third:
>
> While this is ultimately not relevant because the delineation of tags in OSM should be based on verifiable criteria obviously i have never seen any map that displays ocean water and inland waterbodies in differentiated form that shows the Chesapeake Bay as inland water.
>
> Classical examples with differentiated rendering are TPC/ONC (caution: links go to large images):

Pilot maps don't usually have lines deliniating sections of water.  Marine charts do, however.

R,
Eric

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Re: coastline v. water

Tagging mailing list
In reply to this post by Brian M. Sperlongano
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano <[hidden email]> wrote:

> This was fascinating reading.  I do agree that we ought to have a definition for what gets tagged natural=coastline, and I think it's fine if that definition has some subjectivity.
>
> I would offer something as simple as:
>
> "The coastline should follow the mean high tide line.  In some cases this rule would result in the coastline extending an unreasonable distance along the banks of tidal rivers.  In those cases, mappers should identify a reasonable choke point at which to terminate the inland extent of coastline tagging."

I would just classify it as "where the ocean meets the land".  Any other water that isn't ocean should be mapped as water and tagged appropriately.  That makes the map more accurate and detailed.

R,
Eric

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Re: coastline v. water

Joseph Eisenberg
Eric,
I don't think the previous discussion is quite as inconclusive as your evaluation.

While it is true that there is not widespread agreement on where the natural=coatline ways should transect a river mouth or river estuary, there is nearly universal agreement that marginal seas, including bays, are mapped with the natural=coastline.

Using the rendering at https://www.openstreetmap.de/karte.html - which differentiates the marine water polygons outside of the coastline from lakes and rivers, by using slightly different colors, we can see how bays are mapped in other parts of North America and the world. 

For example, check out Delaware Bay, just up the coast from your area: https://www.openstreetmap.de/karte.html?zoom=10&lat=39.14649&lon=-75.07302&layers=B000 - it is mapped as a natural=bay with natural=coastline around it, not natural=water

Upper and Lower New York Bay are mapped as bays outside of the natural=coastline - you can see the line where the waterway=riverbank area starts just at the north end of Manhattan island (though this placement is somewhat controversial) - https://www.openstreetmap.de/karte.html?zoom=10&lat=40.63628&lon=-73.93525&layers=B000



San Francisco Bay and connected bays: https://www.openstreetmap.de/karte.html?zoom=10&lat=37.79939&lon=-122.06911&layers=B000TT - outside of the coastline

Puget Sound - while Lake Washington on the east side of Seattle is natural=water, also most of the ship canal connecting them: https://www.openstreetmap.de/karte.html?zoom=11&lat=47.59544&lon=-122.39252&layers=B000

I would like to request that the tidal channels and estuaries around Chesapeake Bay be re-mapped with natural=coastline. If you wish to keep the natural-water polygons for the estuaries that is not a problem.

But it would be contrary to normal practice to map the main body of Chesapeake Bay as natural=water because it is clearly part of the sea - there is no barrier between it and the open ocean, since there is an open channel through US 13 where the tunnel is. While it is an estuary by hydrological definitions, so are the Baltic Sea and all fjords and Puget Sound and San Francisco Bay - all of which are mapped as outside of the natural=coastline. 

Also please consider that the community here approved the proposal for waterway=tidal_channel which said that the area of tidal channels (aka tidal creeks) should be mapped with natural=coastline at their edges - see https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dtidal_channel#How_to_Map and https://wiki.openstreetmap.org/wiki/Proposed_features/Tag:waterway%3Dtidal_channel - most of the "creek" features along the Bay are tidal channels.

-- Joseph Eisenberg

On Thu, Nov 19, 2020 at 6:46 AM Eric H. Christensen via Tagging <[hidden email]> wrote:
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano <[hidden email]> wrote:

> This was fascinating reading.  I do agree that we ought to have a definition for what gets tagged natural=coastline, and I think it's fine if that definition has some subjectivity.
>
> I would offer something as simple as:
>
> "The coastline should follow the mean high tide line.  In some cases this rule would result in the coastline extending an unreasonable distance along the banks of tidal rivers.  In those cases, mappers should identify a reasonable choke point at which to terminate the inland extent of coastline tagging."

I would just classify it as "where the ocean meets the land".  Any other water that isn't ocean should be mapped as water and tagged appropriately.  That makes the map more accurate and detailed.

R,
Eric

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Re: coastline v. water

Tagging mailing list
You cannot point to other area that may, in fact, be improperly mapped as an example when they are like that because locals have been shouted down for doing it correctly.  The fact that this keeps coming back up literally means that there is not universal agreement that "marginal seas", whatever that means, are to be mapped with natural=coastline. 

The Chesapeake Bay is an estuary that, by definition, opens to the sea.  It can't be a sea and open to a sea at the same time.  In this environment, it is different from the ocean in which it opens into and is also different from the tributaries that feed it.  These are protected waters for ships.  You won't find any high seas forecasts for the Bay unlike the ocean.  The Bay is also brackish and not defined as salt water, unlike the ocean. 

If the rendering engine isn't showing it correctly, fix that; *that's* what's broken.

Eric


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Saturday, November 21, 2020 1:14 PM, Joseph Eisenberg <[hidden email]> wrote:

Eric,
I don't think the previous discussion is quite as inconclusive as your evaluation.

While it is true that there is not widespread agreement on where the natural=coatline ways should transect a river mouth or river estuary, there is nearly universal agreement that marginal seas, including bays, are mapped with the natural=coastline.

Using the rendering at https://www.openstreetmap.de/karte.html - which differentiates the marine water polygons outside of the coastline from lakes and rivers, by using slightly different colors, we can see how bays are mapped in other parts of North America and the world. 

For example, check out Delaware Bay, just up the coast from your area: https://www.openstreetmap.de/karte.html?zoom=10&lat=39.14649&lon=-75.07302&layers=B000 - it is mapped as a natural=bay with natural=coastline around it, not natural=water

Upper and Lower New York Bay are mapped as bays outside of the natural=coastline - you can see the line where the waterway=riverbank area starts just at the north end of Manhattan island (though this placement is somewhat controversial) - https://www.openstreetmap.de/karte.html?zoom=10&lat=40.63628&lon=-73.93525&layers=B000



San Francisco Bay and connected bays: https://www.openstreetmap.de/karte.html?zoom=10&lat=37.79939&lon=-122.06911&layers=B000TT - outside of the coastline

Puget Sound - while Lake Washington on the east side of Seattle is natural=water, also most of the ship canal connecting them: https://www.openstreetmap.de/karte.html?zoom=11&lat=47.59544&lon=-122.39252&layers=B000

I would like to request that the tidal channels and estuaries around Chesapeake Bay be re-mapped with natural=coastline. If you wish to keep the natural-water polygons for the estuaries that is not a problem.

But it would be contrary to normal practice to map the main body of Chesapeake Bay as natural=water because it is clearly part of the sea - there is no barrier between it and the open ocean, since there is an open channel through US 13 where the tunnel is. While it is an estuary by hydrological definitions, so are the Baltic Sea and all fjords and Puget Sound and San Francisco Bay - all of which are mapped as outside of the natural=coastline. 

Also please consider that the community here approved the proposal for waterway=tidal_channel which said that the area of tidal channels (aka tidal creeks) should be mapped with natural=coastline at their edges - see https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dtidal_channel#How_to_Map and https://wiki.openstreetmap.org/wiki/Proposed_features/Tag:waterway%3Dtidal_channel - most of the "creek" features along the Bay are tidal channels.

-- Joseph Eisenberg

On Thu, Nov 19, 2020 at 6:46 AM Eric H. Christensen via Tagging <[hidden email]> wrote:
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano <[hidden email]> wrote:

> This was fascinating reading.  I do agree that we ought to have a definition for what gets tagged natural=coastline, and I think it's fine if that definition has some subjectivity.
>
> I would offer something as simple as:
>
> "The coastline should follow the mean high tide line.  In some cases this rule would result in the coastline extending an unreasonable distance along the banks of tidal rivers.  In those cases, mappers should identify a reasonable choke point at which to terminate the inland extent of coastline tagging."

I would just classify it as "where the ocean meets the land".  Any other water that isn't ocean should be mapped as water and tagged appropriately.  That makes the map more accurate and detailed.

R,
Eric

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Re: coastline v. water

Sarah Hoffmann
Hi,

On Sat, Nov 21, 2020 at 07:09:45PM +0000, Eric H. Christensen via Tagging wrote:
> You cannot point to other area that may, in fact, be improperly mapped as an example when they are like that because locals have been shouted down for doing it correctly. The fact that this keeps coming back up literally means that there is not universal agreement that "marginal seas", whatever that means, are to be mapped with natural=coastline.
>
> The Chesapeake Bay is an estuary that, by definition, opens to the sea. It can't be a sea and open to a sea at the same time. In this environment, it is different from the ocean in which it opens into and is also different from the tributaries that feed it. These are protected waters for ships. You won't find any high seas forecasts for the Bay unlike the ocean. The Bay is also brackish and not defined as salt water, unlike the ocean.

There is a very fundamental misunderstanding on how OpenStreetMap works
in here. The definition of a tag comes from the agreed-on understanding
of the OpenStreetMap community as a whole of what that tag should be. This
may or may not agree with defintion of the same word in other contexts.
That's just the way it is with defintions. They may differ. You cannot just
uniterally apply a definition of coastline that you think is more
appropriate, or scientifically correct or whatever and change the map.
It is OSM's definition that counts, and OSM's defintion only.

That doesn't mean that definitions can't evolve over time but that needs
to be discussed when it has a larger impact. natural=coastline
is a particular touchy tag here because it is one of the few tags where
we rely on a agreed-on definition that works on a planet-scale. Even if
you change something relatively locally, it has an effect on how the
planet map as a whole is rendered. You can't just apply a new definition
to one bay. We must agree on a new definition globally here and apply it
globally or the tagging becomes a worthless mess.

So please, by all means, start a discussion about a new definition of
coastline, make a wiki page, put it up for voting. But all this should
be done **before** making any larger changes. For now, please, put
the Chesapeake Bay back into its original state.

Kind regards

Sarah

> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Saturday, November 21, 2020 1:14 PM, Joseph Eisenberg <[hidden email]> wrote:
>
> > Eric,
> > I don't think the previous discussion is quite as inconclusive as your evaluation.
> >
> > While it is true that there is not widespread agreement on where the natural=coatline ways should transect a river mouth or river estuary, there is nearly universal agreement that marginal seas, including bays, are mapped with the natural=coastline.
> >
> > Using the rendering at https://www.openstreetmap.de/karte.html - which differentiates the marine water polygons outside of the coastline from lakes and rivers, by using slightly different colors, we can see how bays are mapped in other parts of North America and the world.
> >
> > For example, check out Delaware Bay, just up the coast from your area: https://www.openstreetmap.de/karte.html?zoom=10&lat=39.14649&lon=-75.07302&layers=B000 - it is mapped as a natural=bay with natural=coastline around it, not natural=water
> >
> > Upper and Lower New York Bay are mapped as bays outside of the natural=coastline - you can see the line where the waterway=riverbank area starts just at the north end of Manhattan island (though this placement is somewhat controversial) - https://www.openstreetmap.de/karte.html?zoom=10&lat=40.63628&lon=-73.93525&layers=B000
> >
> > Tampa Bay: https://www.openstreetmap.de/karte.html?zoom=10&lat=27.80801&lon=-82.63368&layers=B000 - outside of the natural=coastline
> >
> > Galveston Bay: https://www.openstreetmap.de/karte.html?zoom=10&lat=29.49869&lon=-94.94249&layers=B000TT - outside of the natural=coastline
> >
> > San Francisco Bay and connected bays: https://www.openstreetmap.de/karte.html?zoom=10&lat=37.79939&lon=-122.06911&layers=B000TT - outside of the coastline
> >
> > Puget Sound - while Lake Washington on the east side of Seattle is natural=water, also most of the ship canal connecting them: https://www.openstreetmap.de/karte.html?zoom=11&lat=47.59544&lon=-122.39252&layers=B000
> >
> > I would like to request that the tidal channels and estuaries around Chesapeake Bay be re-mapped with natural=coastline. If you wish to keep the natural-water polygons for the estuaries that is not a problem.
> >
> > But it would be contrary to normal practice to map the main body of Chesapeake Bay as natural=water because it is clearly part of the sea - there is no barrier between it and the open ocean, since there is an open channel through US 13 where the tunnel is. While it is an estuary by hydrological definitions, so are the Baltic Sea and all fjords and Puget Sound and San Francisco Bay - all of which are mapped as outside of the natural=coastline.
> >
> > Also please consider that the community here approved the proposal for waterway=tidal_channel which said that the area of tidal channels (aka tidal creeks) should be mapped with natural=coastline at their edges - see https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dtidal_channel#How_to_Map and https://wiki.openstreetmap.org/wiki/Proposed_features/Tag:waterway%3Dtidal_channel - most of the "creek" features along the Bay are tidal channels.
> >
> > -- Joseph Eisenberg
> >
> > On Thu, Nov 19, 2020 at 6:46 AM Eric H. Christensen via Tagging <[hidden email]> wrote:
> >
> >> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> >>
> >> On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano <[hidden email]> wrote:
> >>
> >>> This was fascinating reading. I do agree that we ought to have a definition for what gets tagged natural=coastline, and I think it's fine if that definition has some subjectivity.
> >>>
> >>> I would offer something as simple as:
> >>>
> >>> "The coastline should follow the mean high tide line. In some cases this rule would result in the coastline extending an unreasonable distance along the banks of tidal rivers. In those cases, mappers should identify a reasonable choke point at which to terminate the inland extent of coastline tagging."
> >>
> >> I would just classify it as "where the ocean meets the land". Any other water that isn't ocean should be mapped as water and tagged appropriately. That makes the map more accurate and detailed.
> >>
> >> R,
> >> Eric
> >>
> >> _______________________________________________
> >> Tagging mailing list
> >> [hidden email]
> >> https://lists.openstreetmap.org/listinfo/tagging

> _______________________________________________
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Re: coastline v. water

David Groom
In reply to this post by Tagging mailing list
See comments below: 

David
------ Original Message ------
From: "Eric H. Christensen via Tagging" <[hidden email]>
Cc: "Eric H. Christensen" <[hidden email]>
Sent: 18/11/2020 20:19:51
Subject: [Tagging] coastline v. water

After a few days of much work, a recent collaborative project to turn the Chesapeake Bay from a nothing space outlined by natural=coastline to what we considered to be a more accurate relation of natural=water, we've received some negative feedback.
 
The difference of opinion seems to lie in the definition of what we're mapping.  The use of coastline is for "seas"[0] while the use of water is for "inland areas of water"[1].  Even though the Chesapeake Bay is tidal, there is no question that it is an inland waterway (it is completely surrounded by land except for the mouth at its southeast side).
Using this logic the Mediterranean Sea, the Red Sea, and the Persian Gulf should all have the coastline tags removed from their defining ways and converted to water areas!   Italy, Greece, Libya, Egypt and a large group of other counties would find they had no coastline, which might come as a surprise to anyone lining there.

The idea of using coastlines for basically creating an edge between the land and the nothingness of the ocean makes sense when, as far as the eye can see it's only water.
 
Now, some of the feedback that has been presented[2] is that because it is tidal it is part of the sea. I have pointed out that many rivers and streams (and ditches!) are tidal; does that make them part of the sea? I would not think so. In fact, there are named seas on this planet that are not even connected to other water formations (the tiniest, according to the National Geographic, is the Sea of Marmara which has an area just less than 12,950 sq km, larger than the Chesapeake Bay).
 
But, tagging the Chesapeake Bay, and its tributaries, as "water" brings several benefits to the map and the users. First, it helps identify the sections of water that exist in these areas (this can't really be done with node points as there is no way to define start and end points of an area). There are many defined bays, rivers, and streams that make up the greater Chesapeake Bay area. What one may see as one large mass of water is actually many smaller defined segments each with their own history.
This is irrelevant to the question of whether the ways should be tagged as natural = coastline.  You have had to create a multipolygon containing the ways which form the "sections of water", its perfectly possible to add the "name" tag to this multipolygon without removing the coastline tag from the ways

Second, we can speed up any updates (fixes) to outlines of the polygons that happen in these water areas without having to wait for the entire Earth's coastlines to be re-rendered.
Changes to tagging should not be done to facilitate easier rendering on one particular map.

I suspect having less coastline to render would also speed up the rendering of coastlines as well?
Very unlikely.

I would like for the tagging community to clarify the different between "water" and "coastline" and when to use each. The definition on water seems to say to use it on inland water but there seems to be, at least, and open interpretation of the word "sea" for coastline that is dragging many inland waters into that category.
 
Thanks,
Eric "Sparks" Christensen
 
 
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Re: coastline v. water

Frederik Ramm
Hi,

On 23.11.20 15:10, David Groom wrote:
> Using this logic the Mediterranean Sea, the Red Sea, and the Persian
> Gulf should all have the coastline tags removed from their defining ways
> and converted to water areas!   Italy, Greece, Libya, Egypt and a large
> group of other counties would find they had no coastline, which might
> come as a surprise to anyone lining there.

I'll probably have to inform the tourism guys in Annapolis too and tell
them to stop calling themselves a "coastal place"
https://patch.com/maryland/annapolis/annapolis-among-20-best-coastal-places-live-magazine
;) sorry folks, you're on an inland waterway. Bit like Richmond really!

Bye
Frederik

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Re: coastline v. water

Brian M. Sperlongano
In reply to this post by Sarah Hoffmann
I've spent a significant amount of time painstakingly re-mapping the crudely-drawn PGS coastal boundaries of Rhode Island to conform to the wiki definition of natural=coastline, having it traverse all the little bays, coves, inlets, etc.  I've also been adding named bodies of water as polygons outside of the coastline ways as these two techniques can coexist just fine.

I would be quite upset if another mapper came along and undid all that work because they didn't like the documented definition and chose to arbitrarily apply a different one.

On Sun, Nov 22, 2020, 3:41 AM Sarah Hoffmann <[hidden email]> wrote:
Hi,

On Sat, Nov 21, 2020 at 07:09:45PM +0000, Eric H. Christensen via Tagging wrote:
> You cannot point to other area that may, in fact, be improperly mapped as an example when they are like that because locals have been shouted down for doing it correctly. The fact that this keeps coming back up literally means that there is not universal agreement that "marginal seas", whatever that means, are to be mapped with natural=coastline.
>
> The Chesapeake Bay is an estuary that, by definition, opens to the sea. It can't be a sea and open to a sea at the same time. In this environment, it is different from the ocean in which it opens into and is also different from the tributaries that feed it. These are protected waters for ships. You won't find any high seas forecasts for the Bay unlike the ocean. The Bay is also brackish and not defined as salt water, unlike the ocean.

There is a very fundamental misunderstanding on how OpenStreetMap works
in here. The definition of a tag comes from the agreed-on understanding
of the OpenStreetMap community as a whole of what that tag should be. This
may or may not agree with defintion of the same word in other contexts.
That's just the way it is with defintions. They may differ. You cannot just
uniterally apply a definition of coastline that you think is more
appropriate, or scientifically correct or whatever and change the map.
It is OSM's definition that counts, and OSM's defintion only.

That doesn't mean that definitions can't evolve over time but that needs
to be discussed when it has a larger impact. natural=coastline
is a particular touchy tag here because it is one of the few tags where
we rely on a agreed-on definition that works on a planet-scale. Even if
you change something relatively locally, it has an effect on how the
planet map as a whole is rendered. You can't just apply a new definition
to one bay. We must agree on a new definition globally here and apply it
globally or the tagging becomes a worthless mess.

So please, by all means, start a discussion about a new definition of
coastline, make a wiki page, put it up for voting. But all this should
be done **before** making any larger changes. For now, please, put
the Chesapeake Bay back into its original state.

Kind regards

Sarah

> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Saturday, November 21, 2020 1:14 PM, Joseph Eisenberg <[hidden email]> wrote:
>
> > Eric,
> > I don't think the previous discussion is quite as inconclusive as your evaluation.
> >
> > While it is true that there is not widespread agreement on where the natural=coatline ways should transect a river mouth or river estuary, there is nearly universal agreement that marginal seas, including bays, are mapped with the natural=coastline.
> >
> > Using the rendering at https://www.openstreetmap.de/karte.html - which differentiates the marine water polygons outside of the coastline from lakes and rivers, by using slightly different colors, we can see how bays are mapped in other parts of North America and the world.
> >
> > For example, check out Delaware Bay, just up the coast from your area: https://www.openstreetmap.de/karte.html?zoom=10&lat=39.14649&lon=-75.07302&layers=B000 - it is mapped as a natural=bay with natural=coastline around it, not natural=water
> >
> > Upper and Lower New York Bay are mapped as bays outside of the natural=coastline - you can see the line where the waterway=riverbank area starts just at the north end of Manhattan island (though this placement is somewhat controversial) - https://www.openstreetmap.de/karte.html?zoom=10&lat=40.63628&lon=-73.93525&layers=B000
> >
> > Tampa Bay: https://www.openstreetmap.de/karte.html?zoom=10&lat=27.80801&lon=-82.63368&layers=B000 - outside of the natural=coastline
> >
> > Galveston Bay: https://www.openstreetmap.de/karte.html?zoom=10&lat=29.49869&lon=-94.94249&layers=B000TT - outside of the natural=coastline
> >
> > San Francisco Bay and connected bays: https://www.openstreetmap.de/karte.html?zoom=10&lat=37.79939&lon=-122.06911&layers=B000TT - outside of the coastline
> >
> > Puget Sound - while Lake Washington on the east side of Seattle is natural=water, also most of the ship canal connecting them: https://www.openstreetmap.de/karte.html?zoom=11&lat=47.59544&lon=-122.39252&layers=B000
> >
> > I would like to request that the tidal channels and estuaries around Chesapeake Bay be re-mapped with natural=coastline. If you wish to keep the natural-water polygons for the estuaries that is not a problem.
> >
> > But it would be contrary to normal practice to map the main body of Chesapeake Bay as natural=water because it is clearly part of the sea - there is no barrier between it and the open ocean, since there is an open channel through US 13 where the tunnel is. While it is an estuary by hydrological definitions, so are the Baltic Sea and all fjords and Puget Sound and San Francisco Bay - all of which are mapped as outside of the natural=coastline.
> >
> > Also please consider that the community here approved the proposal for waterway=tidal_channel which said that the area of tidal channels (aka tidal creeks) should be mapped with natural=coastline at their edges - see https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dtidal_channel#How_to_Map and https://wiki.openstreetmap.org/wiki/Proposed_features/Tag:waterway%3Dtidal_channel - most of the "creek" features along the Bay are tidal channels.
> >
> > -- Joseph Eisenberg
> >
> > On Thu, Nov 19, 2020 at 6:46 AM Eric H. Christensen via Tagging <[hidden email]> wrote:
> >
> >> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> >>
> >> On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano <[hidden email]> wrote:
> >>
> >>> This was fascinating reading. I do agree that we ought to have a definition for what gets tagged natural=coastline, and I think it's fine if that definition has some subjectivity.
> >>>
> >>> I would offer something as simple as:
> >>>
> >>> "The coastline should follow the mean high tide line. In some cases this rule would result in the coastline extending an unreasonable distance along the banks of tidal rivers. In those cases, mappers should identify a reasonable choke point at which to terminate the inland extent of coastline tagging."
> >>
> >> I would just classify it as "where the ocean meets the land". Any other water that isn't ocean should be mapped as water and tagged appropriately. That makes the map more accurate and detailed.
> >>
> >> R,
> >> Eric
> >>
> >> _______________________________________________
> >> Tagging mailing list
> >> [hidden email]
> >> https://lists.openstreetmap.org/listinfo/tagging

> _______________________________________________
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Re: coastline v. water

Frederik Ramm
In reply to this post by Joseph Eisenberg
Hi,

I would like to make one point that has been touched on but not said
clearly, I think.

Some proponents of the recent changes to Chesapeake bay have used
reasoning like: "Only by mapping the bay as a polygon can $SOFTWARE
properly determine that a given location is in the bay, as opposed to in
some undfined part of the sea."

To this, Jochen has even replied along the lines of "create a polygon if
you want but additionally use the natural=coastline tag".

I want to issue a stern warning here: This line of thinking will not
stop with Chesapeake bay. People are already creating giant
multipolygons for the Strait of X and the Gulf of Y all over OSM. Before
too long, a desire to have $SOFTWARE properly decide that a given
location is, say, in the Atlantic Ocean, will give rise to demands that
the Atlantic Ocean be mapped as a giant, named water polygon.

Our current tooling makes this impractical (that's the very reason why
we handle the coastline like we do). Even the 2000+ member "gulfs" and
"bays" and "straits" that some people seem to derive endless pleasure
from plastering the map with - often using questionable third-party
sources or guesswork to define where exactly you leave the ocean and
enter the gulf - already complicate the delicate community processes of
editing and quality assurance. Splitting a single piece of coastline
anywhere along Chesapeake bay now will, for example, give your changeset
a bounding box that encompasses the whole bay. Anyone monitoring local
edits gets swamped with false positives like that. It will also require
uploading a complete new version of the giant bay polygon, vastly
increasing the likelihood of edit conflicts that might well lead a
hapless novice to abandoning their work, rather than trying to solve the
conflict.

Now, you might smirk and say "let's fix the tools then", but until the
tools are fixed - which might take years -, you've made life a hell of a
lot harder for anyone editing or quality monitoring in the whole area.

And all for what - a nice blue label in the bay?

Bye
Frederik

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Re: coastline v. water

Kevin Kenny-3


On Mon, Nov 23, 2020 at 2:57 PM Frederik Ramm <[hidden email]> wrote:
Now, you might smirk and say "let's fix the tools then", but until the
tools are fixed - which might take years -, you've made life a hell of a
lot harder for anyone editing or quality monitoring in the whole area.

And all for what - a nice blue label in the bay?

TL;DR: I understand the technical problems. Don't let the technical problems block the discussion for people who might be able to develop technical solutions.

 

Back when this discussion started, it started because you deleted a relation for the Gulf of Bothnia, entirely without warning, without discussion, and without mentioning it in public even afterward until it was noticed and you were called on it in public. Generally speaking, it was accepted, ex post facto, as an emergency measure needed to rescue the servers from a performance trap, and most of us were willing to accept a temporary moratorium on creating large area relations because of the technical complications.

That issue became complicated because others chimed in and started to argue that, rather than being a measure to rescue the servers from trouble, it was actually a reflection of a universally accepted policy that every millimetre of an area feature's boundary must be unambiguously defined and visible on the ground, and the discussion rapidly deteriorated because that definition, taken to its logical extreme, would exclude virtually all rivers, lakes and streams from being distinct bodies of water, would entirely exclude features such as bays, isthmi, peninsulae, and so on from ever being mapped regardless of size or obvious closure, and in general would dismiss topology as being entirely unimportant. The arguments went as far as to have one user advance the claim that a number of counties and townships north of me should not be mapped, despite having well-defined borders in the inhabited regions, because portions of their boundaries have never been successfully surveyed.

But somehow, those voices never gained entirely the upper hand.  If so, features like `bay`, `peninsula`, `strait`, `isthmus`, `ridge`, `valley` and so on would all bear prominent warnings on the Wiki that it is inappropriate to map them. Somehow, the people who loudly proclaim that objectivity and observability require that every feature be bright-line observable in the field cannot bring themselves to do that, or know that the community would reject it.

For myself, I've deferred to you on the matter - including refraining from mapping even small features like Jamaica Bay (https://www.openstreetmap.org/#map=12/40.6125/-73.8082) - despite the fact that the specific feature is reasonably sized, local, quite different from the Atlantic Ocean (calm water, much lower salinity, much greater tidal range, and a very different ecosystem) and that I would very much like at some point to produce a detailed paper map of my boyhood home town (https://www.openstreetmap.org/relation/174930) including, of course, labeling the waterways that lie only partially within its neatline. I'm willing to accept for now that OSM cannot cope with that requirement and I'll have to develop another system alongside OSM and manage multiple map layers to produce such a thing.

That sort of desire - wishing to include some information about long routes or about area features that are large, diffuse, imprecisely defined, or otherwise difficult - appears to be fairly commonplace, given the number of words that have been expended on the subject here and elsewhere. Those of us to whom the topology of area features is important - for instance, because we produce paper maps and wish to produce normal rendering, including labeling, of area features that extend outside the neatline - rapidly grew frustrated, and eventually the discussion died from exhaustion, as discussions on this list usually do. Meanwhile, there's no indication to mappers (for example, warnings in the popular editors) that creating enormous area features is inappropriate because of inability of the tools to deal with them.

Moreover, those who actually have the technical expertise to experiment with solutions to the problem feel stymied at every turn by the gatekeepers - who may also have the technical expertise, but have a different opinion of the problem's importance. I've talked off-list with several skilled programmers and data analysts who definitely believe that even if a solution were to be developed, it would be rejected. There is certainly zero interest from the gatekeepers in maintaining a discussion of the requirements for such a thing - it turns into 'I haven't seen a good enough solution yet, and I'll know it when I see it,' without an answer to, 'in what way is a given proposal unsatisfactory and how might it improve?' There's a natural temptation to transform, 'this problem is too hard for me to solve in the time I have available' into 'this problem is too hard in relation to its importance', to 'this problem is unimportant to me, and you shouldn't work on it either.'

The gatekeepers do good enough work in general that I'm even willing to accept, 'this problem is too hard in relation to its importance and we will not consider solutions that are offered and prefer not to address it,' but then the project really ought to define these objects as being out of scope.  In that case, though, I think that the tool developers really have to be open to the concept of layers. When mappers are going to the effort of doing these things, it's because they want to have them. A directive of, "you should not want to map this feature," will be controversial to say the least.

People map complex features such as the huge one in Alaska that kicked off the current round of this discussion, or smaller but still troublesome ones like https://www.openstreetmap.org/relation/6360587#map=10/43.3696/-74.0561, because they're actually there in the field. All of the small parcels that make up the latter are signed, at the very least where they front along a road, trail or waterway. The large whole is united by a name, an officer who manages it, a management plan, a web site, and so on - and the locals think of it as a single object despite its diffuse structure. Objects with that complex a topology present management problems. Agreed. But I don't know _how_ many arguments I've been in where someone who really has the management problems on his mind instead argues that the object in some way doesn't exist or isn't deserving of mapping.  It's really important to keep the two arguments separate, or it starts to come across as, 'the data model is fine. Fix your country, or fix your world view (or the world view of your users).'

At the very least, document that the creation of large multipolygons for indefinite features is considered inappropriate, and why, and enlist the aid of the maintainers of the editors to warn about the issue.  Otherwise, you'll continue to see that people do it because they want to see the features on the map and are ignorant of the possible effects.


--
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Re: coastline v. water

Christoph Hormann-2
There seems to be quite a lot of anger and animosity in here - paired and in parts probably caused by a very selective and in parts flat out wrong perception of history so i will try to sketch quickly how the development of mapping of names of parts of waterbodies (that is mostly bays and straits) in OSM developed historically.

For a long time - until a few years back - these features were overwhelmingly mapped with nodes.  This was consensus, not because of technical constraints disallowing something else, but because of the realization that in the vast majority of cases this is perfectly sufficient to document all verifiable information available about the feature in question.  Practically in 2016 there were about 5 percent of all bay features mapped with polygons:

https://github.com/gravitystorm/openstreetmap-carto/issues/2068#issuecomment-191677580

which - generously estimated - probably matches about the percentage of cases where you could argue that with a polygon you could record some verifiable information that cannot recorded with a node or a linear way (which still does not mean the polygon is a good data model for such features, just that it has in those cases - besides all disadvantages - also some advantages over a node or a linear way).

This situation was relatively stable - there were some attempts to suggest universally mapping bays with polygons rather than nodes previously:

https://lists.openstreetmap.org/pipermail/tagging/2014-October/thread.html#19775

which however never reached consensus because of the weighty arguments against this idea and because it was always clear that this would be a non-sustainable strategy for OSM in the long term.

Until early 2018 when OSM-Carto (where merging changes was at that time possible without consensus) added rendering of labels for bay polygons with label size and starting zoom level being determined by the size of the polygon but otherwise with no visual feedback or consideration for the geometry of the polygon:

https://github.com/gravitystorm/openstreetmap-carto/pull/3144

- dismissing warnings about the counterproductive incentives this creates:

https://github.com/gravitystorm/openstreetmap-carto/issues/2068#issuecomment-191677580

This lead to a massive change in mapping activities with some mappers engaging in systematic endeavors of removing bay nodes and  drawing labeling polygons instead.  You can probably say this was by far the most successful attempt at steering mappers into a certain direction ever undertaken by OSM-Carto.  While the relative number of bay polygons compared to nodes only increased from about 5 to 15 percent while very few bays were actually newly mapped the total surface area of bay polygons probably increased by a factor of 100-1000 - many of them evidently pure labeling geometries.  See

https://www.openstreetmap.org/user/imagico/diary/47432

for some examples.  This has lead to some mappers removing such label geometry drawings as non-verifiable and pointless (like the mentioned Gulf of Bothnia) - though practically none of these attempts could make a dent against the massive labeling polygon drawing trends.

What does this have to do with technical limitations or constraints?  Very little.  Technical limitations and performance constraints in rendering have never been a factor speaking against drawing large and non-verifiable labeling polygons.  OSM-Carto and countless other map styles have for many years labeled huge administrative boundary relations without issues and this is not any more difficult for bay polygons.  And if it was an issue the solution would be rather simple:  Precalculating ST_PointOnSurface() on import in osm2pgsql.

The argument against drawing bay and strait polygons is one of practical verifiability and maintainability for the mapper.  This is not a technical issue, this is a social issue.  

Now i completely get the frustration of both mappers and map producers here.  Mappers want their mapping to be shown in good quality in maps and if the only way to achieve that is to draw non-verifiable labeling geometries they are willing to invest significant time and energy into that and rationalize that in various ways.

And for map producers with a rudimentary GIS data analyst background and experience mostly in more or less atomic processing of point, linestring and polygon geometries and their spatial relationships but no deeper background in cartographic data processing specifically, the task of producing high quality labeling from bay nodes and a flat set of coastline ways or the osmcoastline output is a steep hurdle.  And in conventional digital map production from dedicated cartographic databases (in contrast to OSM with its generic geodatabase scope) labeling polygons is the state of the art to manage labeling of course.

The problem we have here is that of a widening gap between the goals and aspirations of the mapper community - which naturally grow as OSM grows in ambitions - and the abilities and engagement in the non-mapping part of the community to develop and satisfy similar ambitions in cartographic quality without outsourcing the hard part of that work to the mappers.  Too many people have followed the illusion for too long that the large corporate OSM data users will provide the necessary support in that field while it turns out (non-surprisingly in my eyes) that they have neither an interest in above average cartographic quality nor in substantially sharing methods and competency in the little work they do in that domain.

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Re: coastline v. water

Brian M. Sperlongano

there were some attempts to suggest universally mapping bays with polygons rather than nodes previously:

https://lists.openstreetmap.org/pipermail/tagging/2014-October/thread.html#19775

which however never reached consensus because of the weighty arguments against this idea and because it was always clear that this would be a non-sustainable strategy for OSM in the long term.

It seems to me that consensus is achieved via three, often overlapping methods, in no particular order:

1.  The proposal process
2.  What's documented on the wiki
3.  How tagging is actually used by mappers and data consumers

Specific discussions on the tagging lists are not necessarily good indicators of consensus because they are often dominated by whomever happens to be shouting the loudest and subscribed to the tagging list at that moment.

With regard to mapping named bodies of water, possibly with fuzzy boundaries, using polygons, the wiki documents that this is an acceptable practice, as long as those polygons aren't too large (though, unhelpfully, without defining what "too large" means).  As you note, osm-carto supports this method of tagging for marginal seas, and mappers have adopted such tagging.

Thus, by wiki, and by actual tagging, and by data consumer usage, there IS consensus - it is acceptable but not required to tag such things as polygons.  We should not expect mappers to read the minds of people that are subscribed to this list or comb through years of mailing list archives to understand how tagging standards have evolved.  The history of how we got here is irrelevant -- what matters is what exists now, what problems it may or may not be causing, and what to do about it going forward.

Since you note that there is not a technical limitation, the argument seems to boil down to "I don't like the standard of verifiability that other mappers are using."  That is a perfectly valid opinion to have, but it does not trump de facto, documented usage.  Given the community acceptance of polygon mapping for smaller marginal seas, it would seem that a formal proposal is the minimum standard required for documenting that there is consensus to change de facto usage.

If this is a truly bad idea, and the arguments against such mapping are so strong, it should be a no-brainer to draft a proposal laying out such arguments so that the broader community can consider them and demonstrate true consensus.

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Re: coastline v. water

Kevin Kenny-3
In reply to this post by Christoph Hormann-2
On Tue, Nov 24, 2020 at 9:23 AM Christoph Hormann <[hidden email]> wrote:
The problem we have here is that of a widening gap between the goals and aspirations of the mapper community - which naturally grow as OSM grows in ambitions - and the abilities and engagement in the non-mapping part of the community to develop and satisfy similar ambitions in cartographic quality without outsourcing the hard part of that work to the mappers.  Too many people have followed the illusion for too long that the large corporate OSM data users will provide the necessary support in that field while it turns out (non-surprisingly in my eyes) that they have neither an interest in above average cartographic quality nor in substantially sharing methods and competency in the little work they do in that domain.

(Brief summary: 1. Many area features are indefinite only at margins that do not have a significant deleterious effect on statistics when analyzed or on the understanding of the map when rendered. 2. Topology still matters - for analyzing or rendering them. 3. Algorithm development needs data to chew on. Blocking the data while waiting for the algorithms is a 'deadly embrace.' 4. Mappers are continuing to enter the data for approximate regions because they understand 1.-3. above. 5. Which argument are you willing to give up in order not to argue against all progress in this domain?) 

In my earlier message, I was speaking not as a mapper looking to enter data, nor as a map user looking for a pretty rendering - although I wear both those hats from time to time - but as a newly-retired applied mathematician (A.B., mathematics, Dartmouth College, MS in electrical engineering, Arizona State University, PhD, computer science, University of Illinois, about forty years of experience with GE, Northrop, Honeywell, and others), with a reasonable background in computational geometry, thinking of what challenges I ought to tackle next.

Given that one of my principal avocations is hiking, my chief rendering interest is not with an endlessly-panning map, as useful as that is; it is with paper maps where labeling must conform with the neatline.  For those maps, simply placing a point for 'label painting' near the center of an indefinite feature is not sufficient. Instead, a first step has to be calculating the intersection of the area feature with the region of interest, leading to one of the results: (a) the area is totally within the region; (b) the area is totally outside the region and may be discarded; (c) the area intersects the region partially and one or more regions of intersection must have labels placed individually. The 'one or more' arises from the fact that a non-convex area feature or a non-convex region of interest (a rectangle, for instance, with a corner cut out for placement of a legend) may yield more than one polygon of intersection.

You have on several occasions advanced the argument that the central label should be enough for this and made a contention that I don't understand about projecting from the central label of a bay onto the shoreline to reconstruct the area. With that contention came the implication that the topological information about an indefinite area would not be needed, if only the renderers and data analysts worked hard enough. Unless you can provide me with literature citations to what you have in mind, I'm afraid that I'll have to dismiss your claim as hand-waving. As far as I can tell, there is no known way to achieve the result that mappers want - or at least I want - without the detailed geometry of the partially indefinite area. If you can provide such citations, I'm eager to follow up with you!

I should digress into the phrase, 'partially indefinite,' that I've already been using.  For the contentious areas such as the Red Sea, the indefinite portion about which the controversy arises is typically small, and typically of a nature where a rough approximation is acceptable to all users. There is no controversy arising from the shoreline of the Red Sea except for a trivial amount of border.  Very few claim that the Red Sea exists only as a social construct. Scientists discuss its hydrology and ecology in contradistinction to that of the region of the Indian Ocean to which it connects.  Mariners speak of Port Sudan, Jeddah, Sharm al-Sheikh, or Eilat as Red Sea ports (Eilat may be further specialised as being a port on the Gulf of Aqaba, a smaller area that is similarly well-defined; the relation is one of hierarchy rather than exclusion. (Moving somewhat to the northwest, I've seen papers on hydrology that have tabulated observations in rows labeled 'Ionian Sea', 'Ægean Sea', 'Tyrrhenian Sea', 'Adriatic Sea', and so on. There is _some_ shared understanding that those words have meanings.)

'Partially indefinite' extends to other features such as peninsulæ (a mirror image of bays - the indefinite boundary is one of land rather than water); straits (indefinite water margins at both ends); isthmi (indefinite land margins at both ends); and even rivers and lakes (indefinite at river mouths, lake inlets and outlets; confluences where tributaries enter, and divergences where distributaries leave). It even extends to political boundaries.  There are a number of townships and even counties in my part of the world where the political boundaries are well known, surveyed, and monumented in the inhabited regions, but have never been successfully surveyed; knowing where the line is in the woods and swamps is simply not worth the cost of mounting a survey. (The general attitude has been, "if it ever becomes an issue, we'll sort it out.")  https://caltopo.com/map.html#ll=43.91623,-74.49297&z=14&b=t indicates one example, where - on an official topo map from the US Geologic Survey - the cartographer has indicated the political boundary as 'INDEFINITE BOUNDARY' and even indicated an error of closure at the northern corner of the township. This is NOT a bad splice between two map sheets; note that streams, lakes, contour lines, are continuous.  The discontinuity of the grid lines arises from the fact that one map sheet shows coordinates in NAD83 (nearly the same as WGS84) while the other is NAD27. The error of closure arises from projecting the boundaries of incomplete surveys that yielded inconsistent results. Still, if you follow the indefinite line around, you eventually come to where it transects the hamlet of Oxbow, https://caltopo.com/map.html#ll=43.43812,-74.49185&z=14&b=t, east of Rudeston and southeast of Piseco, where the town line is indeed signed on the highway (source: personal observation). The inhabitants of Oxbow no doubt care very much about which township collects their property taxes and maintains their roads; whose justice of the peace adjudicates their minor disputes, officiates at their marriages, and so on; whose town clerk maintains their vital statistics.  The reductio-ad-absurdum of your argument would say that the township of Arietta must not be mapped as other than a point feature because large portions of its boundary are indeterminate. The townsfolk would disagree, in light of the fact that such a mapping loses the information of where the town line is, in the places where that's known perfectly well.

Returning to the main point, I don't see how to approach the problem of rendering partially indefinite areas without the geometry of what is known precisely, and some approximation to the indefinite margins so that the areas present a closed, non-self-intersecting topology.  Without that information _somewhere_, there's no place to start from! I would also appreciate some sort of deprecatory tag (`boundary=indefinite` on the way, perhaps, or a role of `outer:indefinite` or `inner:indefinite` on the way within the relation) to indicate where a particular way is arbitrarily added in order to give a partially-indefinite region a complete topology. A renderer is free to refrain from rendering indefinite margins, or to treat them differently in the rendering (like the narrower dashed line and the callout, 'INDEFINITE BOUNDARY' in the government topo above). Statistical analysis is free to make the boundary 'fuzzy' and explore how moving it will affect results. If you find even this approach unacceptable, your argument presents us with an insoluble 'chicken and egg' problem.  Without the data, there is no foundation on which to develop and explore how rendering and statistical algorithms, both known and yet to be developed, perform against the real world. Without the algorithms already in place, you argue, the data ought not to be provided.

In my opinion, the solution of 'outer:indefinite' and 'inner:indefinite' on the role makes more sense, since an object that is indefinite with respect to one object may be perfectly definite with respect to another. Whether a particular bit of coastline on the Bar al-Mandab Strait is or is not fronting on the Red Sea does not make it any less the shoreline of Yemen or Djibouti.

You have also, in the past, argued passionately against 'foreign keys' being present in OSM (for instance, labeling waters in the US with their 'reach codes', which are digital identifiers identifying stream and river segments that are used in diverse government systems in the US) in order to connect it with non-OSM databases. This argument also forecloses on the idea that perhaps mappers should record the topology of these areas externally to OSM , while renderers or analysts should somehow fuse the multiple sources in their rendering or analysis. 

This combination of constraints feels as if you are arguing against the existence of the Red Sea or the Town of Arietta for some other reason, and using whatever argument will block it in the moment.  We can't enter the data regarding indefinite features in OSM. We can't connect to the data regarding indefinite features outside OSM. We can't develop the algorithms without real data to prove them against. We can't have the actual data in the database until the algorithms are developed to consume the data.  What, pray tell, may we do? All I hear from you is arguments against this and that. They are diverse and, taken together, are comprehensive enough, that in the absence of a proposed path forward among them, it is tempting to dismiss them as simple obstructionism.

That's what mappers are doing. They're mapping indefinite area features because they see the potential benefits of doing so, even if the algorithmics have yet to catch up with them.  Until and unless you offer a better alternative, they will continue to work around your objections.

Note that I am not arguing in favor of anything that I have done on the map. In the vanishingly rare cases where I have adjusted a indefinite margin of an object, I've provided detailed discussion of why I believe that the line is the "best possible from the available information," citing sources.  https://www.openstreetmap.org/user/ke9tv/diary/391486 and https://www.openstreetmap.org/user/ke9tv/diary/42951 are examples).  I've refrained from entering any new indefinite objects at Frederik's request, which at the time appeared to be made in his official capacity as DWG member or as OSM board member. (Whether the request actually reflected an official position or was instead made in his personal capacity remains unclear to me.) While I've argued about the definition of 'coastline' here, I've not moved the coastline in the estuarine environment other than to correct obvious errors in the boundary between land and water. The argument (which I've heard in the past, and don't recall from whom) that I'm advancing this argument to justify in retrospect damage that I've already done to the map does not hold water.

So, how do we move forward? Dismissing the Red Sea as a mere social construct is unlikely to achieve consensus. Moreover, social constructs are part of what we map; we live in the human world as well as the physical one. Objects have names; regions have political boundaries; amenities draw tourists; historic sites enjoy protection; and we map all those things. The human world is a world of ambiguity. We can, and should, try to make the map as definite as possible. We must not discard the human view in doing so.
--
73 de ke9tv/2, Kevin

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Re: coastline v. water

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I mentioned the problem of mapping "fuzzy" areas to a friend, who
replied along the lines of "why, of course such areas should be mapped
as functions, taking a point as input and returning a real between 0
(definitely outside) and 1 (definitely inside)!".

I'd rather not have to implement that, though. =)

(And I agree with Kevin about reconstructing an area from a point +
surrounding coastline. I'd like to see at least an outline of an
algorithm for that! Having said that, I also recognise that
gazillion-point polygons to outline Skagerrak, Kattegatt, the North Sea
and what-have-you may not be the prettiest state of things either...)

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