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#1 2017-04-20 01:45:07

vvoovv
Moderator
Registered: 2008-03-04
Posts: 2,156

Looe Rivers as coastlines?

Is there a reason why West Looe River and East Looe River are mapped as coastlines?

I'd like to convert them to natural=water.

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#2 2017-04-20 06:38:44

The Maarssen Mapper
Member
From: Maarssen, NL
Registered: 2010-08-25
Posts: 174

Re: Looe Rivers as coastlines?

The wiki says: "The natural=coastline tag is used to mark the Mean high water spring which is the point of the highest tide. See natural=coastline for all the details."

IIRC the Looe rivers are very steep-sided so from a 2D perspective there's not much difference between MLWS and MHWS. There have been discussions and proposals before (on various wiki pages9 about tidal rivers. It would be a good thing to have a consistent approach of course, but that is not always easy to achieve in OSM....

How would you decide where to put the transition? I am not asking where you would put it in this case, but how would you decide?

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#3 2017-04-20 11:13:28

SK53
Member
Registered: 2009-01-11
Posts: 281

Re: Looe Rivers as coastlines?

This ria features (caused by post-glacial isostatic sinking) are a very common feature of both the South-West Englad peninsula and Britanny. Wikipedia cites the Kingsbridge Estuary as an example where the estuary is disproportionately large for the inflowing waterways.

Geograph has a decent number of pictures of the two estuaries (for instance http://www.geograph.org.uk/photo/1838288). It is clear that the river waterway should be that which is apparent at low tide (with a tidal=yes tag), and that the coastline is broadly correct as it stands.

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#4 2017-04-20 12:15:12

PHerison
Member
From: Oberursel, Germany
Registered: 2008-04-04
Posts: 1,279

Re: Looe Rivers as coastlines?

vvoovv wrote:

...
I'd like to convert them to natural=water.

If you decide to change it, it should be waterway=riverbank I think.

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#5 2017-04-20 12:42:27

vvoovv
Moderator
Registered: 2008-03-04
Posts: 2,156

Re: Looe Rivers as coastlines?

I've taken a look at the pictures from Geograph.

For me the Looe Rivers look like rivers, i.e. not like sea coast.

Image a person comes to the river bank and he doesn't know that river ends at the sea.
What does he see? Sea coast? No! Just a muddy river!

I'd doubt the coastline is the right tag here.

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#6 2017-04-20 18:40:50

The Maarssen Mapper
Member
From: Maarssen, NL
Registered: 2010-08-25
Posts: 174

Re: Looe Rivers as coastlines?

vvoovv wrote:

I've taken a look at the pictures from Geograph.

For me the Looe Rivers look like rivers, i.e. not like sea coast.

Image a person comes to the river bank and he doesn't know that river ends at the sea.
What does he see? Sea coast? No! Just a muddy river!

I'd doubt the coastline is the right tag here.

That depends on your definition of "coastline". For the OSM definition (MHW) it is currently about right.

FYI, OS data shows MHW going right up the East Looe River to this bridge http://www.openstreetmap.org/way/57740639 which is a long way inland...

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#7 2017-04-20 18:55:29

vvoovv
Moderator
Registered: 2008-03-04
Posts: 2,156

Re: Looe Rivers as coastlines?

Personally, I'd stick to "Truth on the ground" principle rather than to a theoretical scientific concept:
What does one see? A river? Then map it as a river!

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#8 2017-04-20 19:29:34

The Maarssen Mapper
Member
From: Maarssen, NL
Registered: 2010-08-25
Posts: 174

Re: Looe Rivers as coastlines?

vvoovv wrote:

Personally, I'd stick to "Truth on the ground" principle rather than to a theoretical scientific concept:
What does one see? A river? Then map it as a river!

What exactly makes it a river? The fact that the water is moving? I mean this as a serious question. OSM tries to make definitions as objective as possible, so you are going to have to be a bit more specific.

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#9 2017-04-21 12:22:22

vvoovv
Moderator
Registered: 2008-03-04
Posts: 2,156

Re: Looe Rivers as coastlines?

Ok, I won't change them, since there are mappers with local knowledge who object to the changes.

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