Re: [Tagging] coastline v. water

2020-11-25 Thread Andy Townsend

Hi,

Recently, Chesapeake Bay (the largest estuary in the United States with a surface area of over 
10,000 sqkm) has been changed from "natural=coastline" tagging to form a large 
"natural=water;water=lagoon" multipolygon instead. The area has also been split into the 
bay itself, the Pocomore Sound, the Tangier Sound, and other smaller bodies.

Current coastline:https://overpass-turbo.eu/s/10xZ  (zoom in or out and 
re-query as desired).

Previous coastline as of 2020-06-01:https://overpass-turbo.eu/s/10y1  (again, 
zoom in or out and rerun the query).

As a consequence, the world-wide coastline processing is stuck. Discussions 
have happened here on this list, as well as on talk-us and on the changeset 
itself:https://www.openstreetmap.org/changeset/94093155

Among the reasons for this change, the following have been mentioned:

* polygon allows better labelling
* polygon allows better geocoding for points on bay water surface
* bay is not really "sea" hence coastline is incorrect
* natural=water tagging allows for quicker turnaround times to see your edits 
on the map
* local mappers should decide how they want stuff tagged

Opponents of the change have said, among other things:

* natural=coastline does not mean "literal" coastline
* a major change like this should be discussed thoroughly before executing
* large polygon hampers editing+QA
* boundaries between water polygons, or between water polygons and sea, are 
arbitrary and not verifiable

The possible solutions to this issue are:

* accept current situation as correct and resume world-wide coastline processing based on 
this as a new "known good" state
* revert the change wholesale and request prior discussion and consensus in the 
community
* any mixture of the above

Following internal discussion within the DWG, we propose the following:

* the polygons that have been created will not be removed

* the land-side members of the polygons for Chesapeake Bay, Tangier Sound, 
Pocomore Sound and potentially others that have been created as part of this  
operation will be given back their natural=coastline tags

In addition, currentlyhttps://www.openstreetmap.org/relation/11884052  is mapped as 
"natural=water; water=lagoon" which does not match the wiki definition 
athttps://wiki.openstreetmap.org/wiki/Tag:water=lagoon  .  
Perhapshttps://wiki.openstreetmap.org/wiki/Tag:natural%3Dbay  would be a better tag?  This is of 
course an entirely separate discussion to where the OSM concept "natural=coastline" 
should go - we don't propose to change the tagging on relation
11884052 now but it probably does need looking at.

This is not intended as a definitive solution for all times, just as a stop-gap 
measure until a consensus is found and, once it has, tools have been amended 
where necessary. Future community discussion may still lead to the removal of 
the coastline tagging, or to the removal of the polygons and their replacement 
by a label point.  For now we're just trying to get to a place where other 
people around the world can make valid coastline edits and see their changes go 
live.  The current impasse over Chesapeake Bay is currently stopping that.

Are the local mappers willing to help implement this? If not, the DWG will do it so that 
normal coastline processing elsewhere can resume.  We apologise in advance to anyone who 
thinks that this is an incorrect decision, but unfortunately sometimes a decision between 
one of two outcomes (neither of which is universally popular) has to be made.  In such 
cases the DWG often reverts to the "status quo ante", and we think that makes 
sense here too.

Best Regards,

Andy Townsend, on behalf of the Data Working Group

On 18/11/2020 20:19, Eric H. Christensen via Tagging 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 

Re: [Tagging] coastline v. water

2020-11-25 Thread Ture Pålsson via Tagging
By the way, an... amusing test case for all things related to water and 
label placement is Lake Mälaren, the lake that Stockholm is separating 
from the sea, and all its (named!) nooks and crannies: 
https://www.openstreetmap.org/relation/1433877 . I've had at least 3 
different bits of it poking into different corners of the map at times.


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Re: [Tagging] coastline v. water

2020-11-25 Thread Paul Allen
On Wed, 25 Nov 2020 at 08:45, Ture Pålsson via Tagging <
tagging@openstreetmap.org> wrote:

>
> (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...)
>

I'm not convinced that point + coastline will give a reasonable result
enough of the time.  But I could be wrong about that.

Polygons that are contiguous with the coastline are a pain to add, even with
generalized coastline (and even worse if Slartibartfast has added crinkly
bits to
the coastline).  It's a lot of work.  If the polygon is crude and not
contiguous
with the coastline that can give bogus results when trying to determine
if a given co-ordinate is in a named bay or not.

However, it is often the case that the ends of bays are known (local
knowledge that village X is in Y bay) or are obvious from inspection.
Since at least one person is confident that a single point is enough
to create a workable algorithm, two points should be twice as good!
Yeah, I was joking, but a lot less code and a lot less algorithmic
guesswork would be involved in marking two points on a coastline
that define the extent of the bay.  An algorithm can generate a bounding
polygon from those two points, the coastline between them, and a straight
line connecting them.  The hardest part would be ensuring that the
algorithm takes the shortest segment of coastline between the two
points and not the longest segment.

Better than two points would be a way joining those two points.
In the absence of further knowledge, map a simple straight line.
A straight line is an approximation because currents and water
depths might mean hydrographers and/or mariners regard the
seaward extent of the bay to be wibbly-wobbly (one of the
examples posted on the list showed a convex seaward extent
of a bay).  So use a way rather than two points to allow for
curvy seaward extents, where known.

Using a way rather than a polygon avoids the problems of
nested bays.  There are many small bays within Cardigan
Bay (mapped by somebody as a polygon):
https://www.openstreetmap.org/way/651881240
It would also deal with the potential problem of
overlapping bays (imperfect nesting), should that
ever be necessary, without mappers having to
jump through hoops constructed of multipolygons.

As far as I can see we can use a point, placed by visual inspection,
and add a tag for importance which determines (in cartos that
make use of it) the size of the label and at what zooms the
label appears.  Or we use a way to determine closure of the bay
and let an algorithm handle placement and importance of the
label.  An algorithm would give greater consistency than mappers
using their best guess at how important the label should be.

Yes, the way could be abused by people wanting to control
placement of the label.  As could the point.  As could any other
way of mapping bays that we come up with.  I don't think
we should reject solutions because somebody could abuse
them, otherwise we wouldn't have any tags at all.

-- 
Paul
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Re: [Tagging] coastline v. water

2020-11-25 Thread Ture Pålsson via Tagging
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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Re: [Tagging] coastline v. water

2020-11-24 Thread Kevin Kenny
On Tue, Nov 24, 2020 at 9:23 AM Christoph Hormann  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 

Re: [Tagging] coastline v. water

2020-11-24 Thread 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: [Tagging] coastline v. water

2020-11-24 Thread Christoph Hormann
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 - 

Re: [Tagging] coastline v. water

2020-11-23 Thread Kevin Kenny
On Mon, Nov 23, 2020 at 2:57 PM Frederik Ramm  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', 

Re: [Tagging] coastline v. water

2020-11-23 Thread Frederik Ramm
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

-- 
Frederik Ramm  ##  eMail frede...@remote.org  ##  N49°00'09" E008°23'33"

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Re: [Tagging] coastline v. water

2020-11-23 Thread Brian M. Sperlongano
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  wrote:

> Hi,
>
> On Sat, Nov 21, 2020 at 07:09:45PM +, 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 <
> joseph.eisenb...@gmail.com> 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=39.14649=-75.07302=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=40.63628=-73.93525=B000
> > >
> > > Tampa Bay:
> https://www.openstreetmap.de/karte.html?zoom=10=27.80801=-82.63368=B000
> - outside of the natural=coastline
> > >
> > > Galveston Bay:
> https://www.openstreetmap.de/karte.html?zoom=10=29.49869=-94.94249=B000TT
> - outside of the natural=coastline
> > >
> > > San Francisco Bay and connected bays:
> https://www.openstreetmap.de/karte.html?zoom=10=37.79939=-122.06911=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=47.59544=-122.39252=B000
> > >
> > > I 

Re: [Tagging] coastline v. water

2020-11-23 Thread 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

-- 
Frederik Ramm  ##  eMail frede...@remote.org  ##  N49°00'09" E008°23'33"

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Re: [Tagging] coastline v. water

2020-11-23 Thread David Groom

See comments below:

David
-- Original Message --
From: "Eric H. Christensen via Tagging" 
To: "tagging@openstreetmap.org" 
Cc: "Eric H. Christensen" 
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

[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: [Tagging] coastline v. water

2020-11-22 Thread Sarah Hoffmann
Hi,

On Sat, Nov 21, 2020 at 07:09:45PM +, 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 
>  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=39.14649=-75.07302=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=40.63628=-73.93525=B000
> >
> > Tampa Bay: 
> > https://www.openstreetmap.de/karte.html?zoom=10=27.80801=-82.63368=B000
> >  - outside of the natural=coastline
> >
> > Galveston Bay: 
> > https://www.openstreetmap.de/karte.html?zoom=10=29.49869=-94.94249=B000TT
> >  - outside of the natural=coastline
> >
> > San Francisco Bay and connected bays: 
> > https://www.openstreetmap.de/karte.html?zoom=10=37.79939=-122.06911=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=47.59544=-122.39252=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 

Re: [Tagging] coastline v. water

2020-11-21 Thread Eric H. Christensen via Tagging
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 
 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=39.14649=-75.07302=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=40.63628=-73.93525=B000
>
> Tampa Bay: 
> https://www.openstreetmap.de/karte.html?zoom=10=27.80801=-82.63368=B000
>  - outside of the natural=coastline
>
> Galveston Bay: 
> https://www.openstreetmap.de/karte.html?zoom=10=29.49869=-94.94249=B000TT
>  - outside of the natural=coastline
>
> San Francisco Bay and connected bays: 
> https://www.openstreetmap.de/karte.html?zoom=10=37.79939=-122.06911=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=47.59544=-122.39252=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 
>  wrote:
>
>> ‐‐‐ Original Message ‐‐‐
>>
>> On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano 
>>  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,

Re: [Tagging] coastline v. water

2020-11-21 Thread 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=39.14649=-75.07302=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=40.63628=-73.93525=B000

Tampa Bay:
https://www.openstreetmap.de/karte.html?zoom=10=27.80801=-82.63368=B000
- outside of the natural=coastline

Galveston Bay:
https://www.openstreetmap.de/karte.html?zoom=10=29.49869=-94.94249=B000TT
- outside of the natural=coastline

San Francisco Bay and connected bays:
https://www.openstreetmap.de/karte.html?zoom=10=37.79939=-122.06911=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=47.59544=-122.39252=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 <
tagging@openstreetmap.org> wrote:

> ‐‐‐ Original Message ‐‐‐
>
> On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano <
> zelonew...@gmail.com> 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: [Tagging] coastline v. water

2020-11-19 Thread Eric H. Christensen via Tagging
‐‐‐ Original Message ‐‐‐

On Wednesday, November 18th, 2020 at 11:34 PM, Brian M. Sperlongano 
 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: [Tagging] coastline v. water

2020-11-19 Thread Eric H. Christensen via Tagging
‐‐‐ Original Message ‐‐‐

On Wednesday, November 18th, 2020 at 5:04 PM, Christoph Hormann 
 wrote:

> > Eric H. Christensen via Tagging tagging@openstreetmap.org 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: [Tagging] coastline v. water

2020-11-18 Thread 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  wrote:

> > Eric H. Christensen via Tagging  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: [Tagging] coastline v. water

2020-11-18 Thread Christoph Hormann
> Eric H. Christensen via Tagging  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: [Tagging] coastline v. water

2020-11-18 Thread Colin Smale
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"
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Re: [Tagging] coastline v. water

2020-11-18 Thread Eric H. Christensen via Tagging
‐‐‐ Original Message ‐‐‐

On Wednesday, November 18th, 2020 at 3:31 PM, 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. 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: [Tagging] coastline v. water

2020-11-18 Thread 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 <
tagging@openstreetmap.org> 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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[Tagging] coastline v. water

2020-11-18 Thread Eric H. Christensen via Tagging
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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