[OSM-talk] the coastline

Elizabeth Dodd edodd at billiau.net
Mon Mar 21 22:19:34 GMT 2011


On Mon, 21 Mar 2011 21:59:20 -0000
"Andy Robinson" <ajrlists at gmail.com> wrote:

> I'd place the coastline at the low water mark because you know then
> that its always true. The coastline at the high water mark is only
> true a couple of times a day or whatever. Then it needs a
> high_water_mark way adding and ideally rendered in the long run.
> 
> Cheers
> Andy
> 
> -----Original Message-----
> From: Robin Paulson [mailto:robin.paulson at gmail.com] 
> Sent: 21 March 2011 21:46
> To: OSM Talk
> Subject: [OSM-talk] the coastline
> 
> i've recently been doing some mapping around auckland, adding coastal
> walkways. one in particular i walked on sunday has two routes: one at
> the foot of the cliffs, one on the road at the top of the cliffs. the
> lower route is under water when the tide is in, so walkers are
> advised to follow the road route.
> 
> so, i added the route, and it is now under water:
> http://www.openstreetmap.org/?lat=-36.927322&lon=174.709115&zoom=18&layers=M
> 
> this seems wrong, drawing a route which is then under water, but the
> alternative of moving the path is also wrong.
> 
> so, what do we do?
> 
> the question becomes (in my mind): why do we have a single way mapped
> 'coastline'? this implies the boundary between land and water is
> static, but of course it moves - a number of times per day.
> 
> i like the possibility of a high water mark and a low water mark, used
> together to entirely replace the natural=coastline tag.
> 
> perhaps some of you have some ideas around this also?
> 
> thanks,
> 
> --

the Coastline has been defined as high water mark.

http://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline

I don't see that redefining it is going to be helpful

Robin's point stands - should we mark the low water mark and the high
water mark and render the littoral zone differently?
I guess it is part of the micro-mapping initiative which is popular on
the tagging list.

From a safety point of view, I'd rather know that the path is under
water. Then I can examine the coast and the tide tables (or ask) and
make a decision on walking it.
I certainly don't want a router taking me through there as the shortest
or fastest walk.



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