[Tagging] Coastal beach definition for mapping.

Warin 61sundowner at gmail.com
Tue Apr 3 21:56:26 UTC 2018


On 03/04/18 18:32, Christoph Hormann wrote:
> On Monday 02 April 2018, Warin wrote:
>> The present OSM wiki defintion for beach
>>
>> is "Coastal beaches should be mapped down to the mean high water
>> spring line (natural
>> <https://wiki.openstreetmap.org/wiki/Key:natural>=coastline
>> <https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline>)"
>>
>> (from https://wiki.openstreetmap.org/wiki/Tag:natural=beach)
>>
>> I think this is incorrect .. they should be mapped past the high
>> water mark to the low water mark.
> This has been a disputed subject for a long time.  In any case the wiki
> clearly does not reflect the current use of the tag here though.  The
> following situations exist frequently in reality:
>
> a) coast at high water line, beach only above high water line.  This
> leads to very narrow beaches since the area correctly to be tagged as a
> beach is only between the regular high water line and the extreme
> (storm flood) high water line.
>
> b) coast at high water line, beach down to lower end of beach (either
> the low water line or the transit of the beach to a tidal flat -
> sometimes, in particular in the UK, the tidal flat is also incorrectly
> tagged natural=beach).
>
> c) coast at an intermediate water level (the level shown in whatever
> image is used), beach ends at this water level (i.e. mappers directly
> draw what they see in the image).
>
> All variants are common, (a) in my experience is not more common than
> (b).
>
> For clarity regarding the difference between beaches and tidal flats:  A
> beach is formed by waves, it therefore always has a significant slope
> and is rarely wider than a few hundred meters.  A tidal flat is a flat
> area exposed at low tide that is shaped by the tidal currents.
>
Thanks Christoph, had not considered 'tidal flats'...
there are some large areas I know of ...
was thinking about them while I considered 'beaches', but had not considered the term 'tidal flats'.




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