Re: [Tagging] Definition of a Beach

2019-08-15 Thread Christoph Hormann
On Thursday 15 August 2019, ael wrote:
>
> I was going to comment that a beach has to meet the water at the same
> level. That is maybe sort of implied above? As opposed to a cliff or
> even wall.

The beach being composed of loose material and being formed by water 
waves implies the beach and the water level intersect and the slope 
being limited.

> I am not sure that a beach is required to have a "significant" slope.

The slope necessarily forms if loose material is being deposited and 
shaped by waves.  As Josef said if the slope is very small the waves 
will not be the dominating force shaping the coast any more and tidal 
currents will be the force shaping the area.  How steep and how wide 
the slope is depends on the relationship of tides, waves and grain size 
of the material.

There are of course also borderline cases to and combinations with other 
coastal land forms like spits, longshore bars etc.  There might also be 
artificial beach nourishment measures that modify the profile.  So 
beaches will not necessarily have a continuous slope everywhere.  But a 
slope on which waves break and water washes up and down with each wave 
is a defining element of a beach.

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

___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Paul Allen
On Thu, 15 Aug 2019 at 13:06, Joseph Eisenberg 
wrote:

> If there is no slope in the area between the low and high tide line,
> and no wave action, you usually get a wetland=tidalflat (mud flat), or
> salt marsh, or mangroves, depending on the climate, not a beach.
>

Sometimes wetland even if there is a slope. Depends on all sorts of
factors.  There's
a continuum between beach and wetland.  Not a very broad one, but it's
there.  Mostly
it will obviously be one or the other, but there are bound to be
exceptions.  A wetland
in monsoon season might be a beach outside of that season.  Unlikely but
possible.

-- 
Paul
___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Joseph Eisenberg
If there is no slope in the area between the low and high tide line,
and no wave action, you usually get a wetland=tidalflat (mud flat), or
salt marsh, or mangroves, depending on the climate, not a beach.

- Joseph

On 8/15/19, Paul Allen  wrote:
> On Thu, 15 Aug 2019 at 12:41, ael  wrote:
>
>>
>> I was going to comment that a beach has to meet the water at the same
>> level. That is maybe sort of implied above? As opposed to a cliff or
>> even wall.
>>
>
> With a cliff the high water and low water marks would be coincident, or
> very nearly
> so.  Unless there is at least enough space for somebody to stand between
> high-
> and low-water marks, it can't be a beach.
>
> I am not sure that a beach is required to have a "significant" slope.
>> Obviously it must have some non-zero slope, otherwise it will be covered
>> by the water (to a first approximation). But on reflection, even that
>> may not be true for some sections of a beach. Portions that may be
>> exposed at low tide could even have a negative slope, and still be a
>> (hazardous) beach.
>>
>
> I wouldn't say a slope is required, just that in the real world there will
> be a slope.
> The point I think was trying to be made is that the slope isn't vertical or
> so steep
> that it's difficult to walk on.  But I could be wrong.
>
> --
> Paul
>

___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Paul Allen
On Thu, 15 Aug 2019 at 12:41, ael  wrote:

>
> I was going to comment that a beach has to meet the water at the same
> level. That is maybe sort of implied above? As opposed to a cliff or
> even wall.
>

With a cliff the high water and low water marks would be coincident, or
very nearly
so.  Unless there is at least enough space for somebody to stand between
high-
and low-water marks, it can't be a beach.

I am not sure that a beach is required to have a "significant" slope.
> Obviously it must have some non-zero slope, otherwise it will be covered
> by the water (to a first approximation). But on reflection, even that
> may not be true for some sections of a beach. Portions that may be
> exposed at low tide could even have a negative slope, and still be a
> (hazardous) beach.
>

I wouldn't say a slope is required, just that in the real world there will
be a slope.
The point I think was trying to be made is that the slope isn't vertical or
so steep
that it's difficult to walk on.  But I could be wrong.

-- 
Paul
___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread ael
On Thu, Aug 15, 2019 at 10:26:55AM +0200, Christoph Hormann wrote:
> On Thursday 15 August 2019, Warin wrote:
> > What is a beach?
> 
> * there are waves breaking, at least at some times, at the water line.
> * ground has a significant slope so waves roll up the beach and water 

I was going to comment that a beach has to meet the water at the same
level. That is maybe sort of implied above? As opposed to a cliff or
even wall.

I am not sure that a beach is required to have a "significant" slope.
Obviously it must have some non-zero slope, otherwise it will be covered
by the water (to a first approximation). But on reflection, even that
may not be true for some sections of a beach. Portions that may be
exposed at low tide could even have a negative slope, and still be a
(hazardous) beach.

ael


___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Christoph Hormann
On Thursday 15 August 2019, Warin wrote:
> What is a beach?
>
> [...]

The question you actually wanted to ask i think is what does 
natural=beach mean in OSM.  This distinction between the meaning of a 
tag in OSM and the meaning of the terms used for key and value in 
English language is very important to keep in mind, in particular for 
native English speakers.

I had a thorough look at use of natural=beach in OSM back when i changed 
rendering in OSM-Carto and came to the conclusion that use of this is 
actually reasonably close to the core scientific definition of beaches, 
namely a wave formed accumulation of loose material at the shore of a 
waterbody.

See also

http://blog.imagico.de/reefs-and-beaches-in-the-openstreetmap-standard-style/

There are a number of notable exceptions from this

* natural=beach is also used for human made artificial beaches where 
sand does not occur naturally.  This is obvious since this is often 
hard to distinguish for the casual observer without in depth research.
* some use of natural=beach for rocky shores exists but it is minimal.
* sometimes use of natural=beach extents on costal dunes which are not 
water formed and therefore not part of the actual beach.
* in particular in the UK there is some atypical use of the tag - based 
on historic practice and use of OS data as a source apparently - of 
using natural=beach for what is indicated as 'Sand' in OS maps and 
wetland=tidalflat (or historically natural=mud) for what OS maps show 
as 'Mud'.  This is distinctly different from elsewhere in particular 
since it uses natural=beach for sand based tidal flats - like here

https://www.openstreetmap.org/way/67573161

How can you identify a beach on the ground:

* there are waves breaking, at least at some times, at the water line.
* ground has a significant slope so waves roll up the beach and water 
flows back in the typical fashion leaving a fairly smooth surface.
* the ground material grain size is somewhere between fine sand and 
medium sized stones - small enough to be moved by the waves when they 
are strong and large enough not to be suspended in and carried away by 
the water as the waves break.
* there are no tidal channels forming in the loose material since these 
are indicative of a tide dominated situation and not a wave dominated 
one - such cases would be suited to map with natural=wetland + 
wetland=tidalflat.

Where there is considerable variation is if and how the tidal part of a 
beach is mapped.  Mainly the following variants exist:

* mapping only the part of the beach above the high water line leading 
to a very narrow beach.
* the tidal part of the beach being mapped as or included in a tidal 
flat.
* the beach crossing the coastline and including the tidal part.
* the coastline being placed not at the high water mark but below, 
usually whereever the imagery used shows the water edge and ending the 
beach at this line.

This would be good to clear up and establish a well defined and 
intuitively usable mapping scheme.

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

___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Warin

On 15/08/19 16:40, Joseph Eisenberg wrote:

Re: > “It would usually be "the area above the Low Tide mark”

Agreed. Many people map this way, which means that the part of the 
beach between the low tide and hight tide lines is outside of the 
coastline. The Openstreetmap-carto style was recently changed to 
handle this.


Some places claim a beach is there .. but it is completely covered by 
high tide.
So to fit their usage I would think a beach is from low tide to at least 
high tide ...
After all if you are there at low tide I think you'd call the area above 
the present water line (even though it is low tide) a beach.


A beach may extend above the hight tide mark if the surface material 
also continues unbroken.
I think we can agree that sand from the low tide to the hight tide mark 
and then to, say, a board walk is all one beach?


But what about other surfaces?
Pebbles? Pebbles up to what size (at some size they become rocks)?
And so on for other surfaces.


___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Joseph Eisenberg
Re: > “It would usually be "the area above the Low Tide mark”

Agreed. Many people map this way, which means that the part of the beach
between the low tide and hight tide lines is outside of the coastline. The
Openstreetmap-carto style was recently changed to handle this.
___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-15 Thread Graeme Fitzpatrick
On Thu, 15 Aug 2019 at 14:50, Warin <61sundow...@gmail.com> wrote:

> On 15/08/19 14:16, Mateusz Konieczny wrote:
>
> Main problem with such definition is that strip of concrete/asphalt along
> shore
> is not a beach.
>
> I thought about dunes when I claimed that "beach is not
> always unvegetated" but now I see that dunes are not considered as part of
> the beach.
>
> I copied definition from Wikipedia as it seemed far better as it managed to
> exclude stuff like
> https://commons.wikimedia.org/wiki/File:Sea_defences_(21467789266).jpg
>
>
> https://commons.wikimedia.org/wiki/File:Mole_in_Funchal,_Ponta_do_Garajau,_statue_of_Cristo_Rei_and_Desertas_Islands._Madeira,_Portugal.jpg
>
>
> https://commons.wikimedia.org/wiki/File:Concrete_defences_by_the_Saxon_Shore_way_-_geograph.org.uk_-_1240179.jpg
>
> Maybe copying previous definition from natural=beach would be preferable.
>
>
> Don't know .. hence my question here .. any 'beach' 'experts'?
>

Lived beside them all my life so I'll have a go!

I'll agree with Mateusz that concrete & boulders aren't a beach - a couple
of those examples I'd probably call man_made=groyne + natural=rock (& yes,
that's because it then renders as rock!), however you can have (isolated)
boulders on a beach.

What is a beach though is a bit tricky, especially for OSM.

It would usually be "the area above the Low Tide mark" but that then
clashes with OSM Coastline, which is taken as the High Tide mark, so that
would then have to mean that the beach is

"The area between the High Tide mark & any adjoining vegetation /
structures / landforms". It's usually largely unvegetated (but may have
isolated trees, clumps of grass etc), & is made up of natural materials
such as sand, pebbles, shells etc"

How's that sound?

Thanks

Graeme
___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-14 Thread Warin

On 15/08/19 14:16, Mateusz Konieczny wrote:




15 Aug 2019, 03:43 by joseph.eisenb...@gmail.com:

For context: yesterday Mateusz Konieczny edited the description of
natural=beach on the Landuse page and commented that "beach is not
always unvegetated and concrete along shore is not a beach", and then
I used his new description on the natural=beach page.

My edit was triggered by 
https://wiki.openstreetmap.org/w/index.php?title=Landuse=prev=1889234

edit that claimed that beach is well defined by
"Unvegetated strip of land at the edge of water."


And that was paraphrased form the original OSM description of a beach.


Main problem with such definition is that strip of concrete/asphalt 
along shore

is not a beach.

I thought about dunes when I claimed that "beach is not
always unvegetated" but now I see that dunes are not considered as 
part of the beach.


I copied definition from Wikipedia as it seemed far better as it 
managed to

exclude stuff like
https://commons.wikimedia.org/wiki/File:Sea_defences_(21467789266).jpg 



https://commons.wikimedia.org/wiki/File:Mole_in_Funchal,_Ponta_do_Garajau,_statue_of_Cristo_Rei_and_Desertas_Islands._Madeira,_Portugal.jpg

https://commons.wikimedia.org/wiki/File:Concrete_defences_by_the_Saxon_Shore_way_-_geograph.org.uk_-_1240179.jpg

Maybe copying previous definition from natural=beach would be preferable.


Don't know .. hence my question here .. any 'beach' 'experts'?


Re: > "To me it does not have plants growing on it - so unvegetated."

I agree that beaches generally don't have surface plants like grass -
this can be found in wind-formed sand dunes next to some beaches,
which I would map as natural=sand or natural=dune + surface=grass if
relevant.

However, there are many beaches shaded by coconut palms and other
spreading or leaning trees here in the rainy tropics - the canopy
would extend out over the high tide water line, so the leaves cover a
significant part of the beach (5 or even 10 meters), and most mappers
put the boundary of natural=wood at the end of the canopy. So I don't
know if mentioning "un-vegetated" in the description is necessary.

So it seems that maybe I managed to improve it, but purely by accident.

Overall I am fine also with older definition from natural=beach, page 
but I strongly
oppose defining beaches as "Unvegetated strip of land at the edge of 
water."


Good point about concrete may not be a 'beach' .. but then what is a 
'beach'?



___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-14 Thread Mateusz Konieczny



15 Aug 2019, 03:43 by joseph.eisenb...@gmail.com:

> For context: yesterday Mateusz Konieczny edited the description of
> natural=beach on the Landuse page and commented that "beach is not
> always unvegetated and concrete along shore is not a beach", and then
> I used his new description on the natural=beach page.
>
My edit was triggered by 
https://wiki.openstreetmap.org/w/index.php?title=Landuse=prev=1889234
 

edit that claimed that beach is well defined by
"Unvegetated strip of land at the edge of water."

Main problem with such definition is that strip of concrete/asphalt along shore
is not a beach.

I thought about dunes when I claimed that "beach is not
always unvegetated" but now I see that dunes are not considered as part of the 
beach.
I copied definition from Wikipedia as it seemed far better as it managed to
exclude stuff like 
https://commons.wikimedia.org/wiki/File:Sea_defences_(21467789266).jpg 


https://commons.wikimedia.org/wiki/File:Mole_in_Funchal,_Ponta_do_Garajau,_statue_of_Cristo_Rei_and_Desertas_Islands._Madeira,_Portugal.jpg
 


https://commons.wikimedia.org/wiki/File:Concrete_defences_by_the_Saxon_Shore_way_-_geograph.org.uk_-_1240179.jpg
 


Maybe copying previous definition from natural=beach would be preferable.


> Re: > "To me it does not have plants growing on it - so unvegetated."
>
> I agree that beaches generally don't have surface plants like grass -
> this can be found in wind-formed sand dunes next to some beaches,
> which I would map as natural=sand or natural=dune + surface=grass if
> relevant.
>
> However, there are many beaches shaded by coconut palms and other
> spreading or leaning trees here in the rainy tropics - the canopy
> would extend out over the high tide water line, so the leaves cover a
> significant part of the beach (5 or even 10 meters), and most mappers
> put the boundary of natural=wood at the end of the canopy. So I don't
> know if mentioning "un-vegetated" in the description is necessary.
>
So it seems that maybe I managed to improve it, but purely by accident.

Overall I am fine also with older definition from natural=beach, page but I 
strongly 
oppose defining beaches as "Unvegetated strip of land at the edge of water."
___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging


Re: [Tagging] Definition of a Beach

2019-08-14 Thread Joseph Eisenberg
For context: yesterday Mateusz Konieczny edited the description of
natural=beach on the Landuse page and commented that "beach is not
always unvegetated and concrete along shore is not a beach", and then
I used his new description on the natural=beach page.

Re: > "Is mud not a beach?"

Generally beaches are formed from sand or larger mineral particles, up
to cobble-sized stones, deposited by moving water. Smaller mineral
particles are carried away by the water.

Mud is formed from mainly wet silt and clay - these are small and very
small mineral particles (clay is so fine that it feels smooth, silt
still feels a little gritty to the touch), which only settle out in
slow moving water.

At the coastline, mud is found at tidal flats ("mud flats"), not on
beaches. These are tagged natural=wetland + wetland=tidalflat

Re: > What about rock?

In British English (and OSM), "Rock" generally means bedrock. The
images of Marino Rocks Beach show an area of round cobblestones up
higher on the sloped beach, and then areas of exposed bedrock lower
down. Solid rock can be mapped as natural=bare_rock (this rock is
probably outside of the coastline, but that's ok if it's above the low
tide line), and the beach area (loose stones) with natural=beach +
surface=stones or =shingle.

Sometimes you also find rough, jagged stones next to a beach where
they have fallen from a cliff: this can be mapped as natural=scree.

Along rivers, areas of rounded stones and pebbles are usually mapped
as natural=shingle rather than natural=beach.

Re: > "To me it does not have plants growing on it - so unvegetated."

I agree that beaches generally don't have surface plants like grass -
this can be found in wind-formed sand dunes next to some beaches,
which I would map as natural=sand or natural=dune + surface=grass if
relevant.

However, there are many beaches shaded by coconut palms and other
spreading or leaning trees here in the rainy tropics - the canopy
would extend out over the high tide water line, so the leaves cover a
significant part of the beach (5 or even 10 meters), and most mappers
put the boundary of natural=wood at the end of the canopy. So I don't
know if mentioning "un-vegetated" in the description is necessary.

-Joseph

On 8/15/19, Warin <61sundow...@gmail.com> wrote:
> What is a beach?
>
> Oxford Dictionary: A pebbly or sandy shore, especially by the sea
> between high- and low-water marks.
>
> OSM description now: landform along a body of water which consists of
> sand, shingle or other loose material
>
> OSM description yesterday: Unvegetated strip of sand, shingle or other loose
> material at the
> coast or the shore of a lake
>
> OSM text: Thenatural =beach
>  tag is used to mark a loose geological landform along the coast or
> along another body of water consisting of sand, gravel, shingle, pebbles,
> cobblestones or sometimes shell fragments etc.
>
> --
>
> To me it does not have plants growing on it - so unvegitated.
>
> Is mud not a beach?
> Merseyside?https://www.adelaidenow.com.au/news/national/rnli-rescue-dog-walker-stuck-in-mud-on-merseyside-beach/video/f52508898923c2dc9907202049229bbe
>
>
> https://www.niwa.co.nz/coasts-and-oceans/nz-coast/learn-about-coastal-environments/beach-types/13-beach-types/reflective-tidal-mud-flats
>
> What about rock?
>
> https://www.weekendnotes.com/marino-rocks-beach/
>
>

___
Tagging mailing list
Tagging@openstreetmap.org
https://lists.openstreetmap.org/listinfo/tagging