[Talk-GB] UK coastline data

Colin Smale colin.smale at xs4all.nl
Thu Jul 11 21:22:03 UTC 2019

On 2019-07-11 22:45, Borbus wrote:

> On Thu, Jul 11, 2019 at 9:19 PM Colin Smale <colin.smale at xs4all.nl> wrote:
>> * Coastal admin boundaries (the "Extent of the Realm") are usually MLWS,
>> but there are such things as "seaward extensions" which extend the
>> "realm" further into the water. Check out for example Brighton Marina,
>> Torbay, City of Bristol.
> I have noticed the boundaries often correspond with MLW. I have tried to
> leave the boundaries alone even when they overlap with the MLW because I
> thought combining them might be confusing.

Combining them might actually be the right thing to do. As a matter of
law the local government jurisdiction extends to MLWS (except where
explicitly otherwise defined) so it should be a question of choosing the
best data, probably the data from the most recent survey. Don't forget
sandbanks and other areas that fall dry at low water - these are also
marked by the OS with MLWS and are therefore admin boundaries. 

>> * Where the "coastline" crosses the mouth of a river or estuary, there
>> has been lots of discussion about this in the past, as usual without a
>> clear definitive verdict. The OS data will take you upstream to the
>> tidal limit of rivers, which sometimes gives results which some people
>> find undesirable. Example: River Dart in Devon.
> Yes, this was something I meant to ask as well. Often the coastlines
> cross the rivers at completely arbitrary points. Thinking about it too
> much brings up the famous coastline paradox. Mapping it right back to
> the tidal limit does seem like the only way that isn't arbitrary. The
> Dart cuts the coastline off right at the mouth, which doesn't seem right
> at all to me. It would be good to be consistent.

I couldn't agree more! My vote is to go back to the tidal limit, for
exactly that reason. 

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