[Talk-GB] UK coastline data

Borbus borbus at gmail.com
Sat Jul 13 11:35:01 UTC 2019

On Fri, Jul 12, 2019 at 9:11 PM Devonshire <maps at fortyfivekev.co.uk> wrote:
> Just because the coastline follows MLW as it goes around the coast
> doesn't mean it needs to follow every tidal waterway inland. That
> doesn't follow at all.

Why not? What is the meaning of "coastline"?

The Dart is one example of where it seems obvious where to "draw the
line" by taking a cursory glance at aerial imagery, but does this line
have any bearing on reality?

My feeling is that the natural=coastline tag is a misnomer and it should
really just be called "mean_high_water_level" or
"mean_high_water_spring" (I'm still unsure about whether OS show MHWL or
MHWS, I thought it was MHWL, which is between mean high water spring and
mean high water neap).

Is there a meaning to "coastline" that makes it distinct from any other
high water level that can't be expressed with other tags? (Other tags
could be water salinity, presence of beaches, dunes, cliffs etc. that
are real physical features).

> To achieve what you want you would need to add yet another way inside of
> the riverbank and intertidal areas which seems like a fair bit of effort
> to do for every river for no real benefit to map users whatsoever. Then
> you need to get it all to render right where you have tidal mud banks,
> etc. in the centre of the river.

That data is included with the OS tidal waters data. It's not much more
effort to use it and it's very useful data for many people. People use
maps for many different things. Rendering is not a problem. Carto
handles it just fine already. But it does expect the intertidal zone to
be between a "coastline" and the edge of a tidalflat.

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