[Talk-ca] Clean up - natural coastline

[David Groom]

----- Original Message ----- 
From: "Andrew Allison" <andrew.allison at teksavvy.com>
To: "talk-ca" <talk-ca at openstreetmap.org>
Sent: Saturday, January 28, 2012 3:33 PM
Subject: [Talk-ca] Clean up - natural coastline


> Hello:
> I'm in the process of recreating non-ct data.
>
> Any gotchas that I should look out for in replacing coastline data.

2 main ones -

A) direction ( see below),

B)  coastline ways when taken together should always form an unbroken line 
around a land mass.

minor "gotchas"

C)  the coastline import from PGS caused a number of small "artefacts" to be 
created, (many 3 node triangles of coastline appearing).  These are not true 
coastline, so need to be dealt with.

D) In places the coastline import was run over an area which was well inland 
of the true coast. The import found water bodes (lakes and rivers) in these 
areas, and created them as coastline.  When recreating these ways it would 
make sense to tag these correctly.  Note very large lakes may still have to 
be tagged as coastline however.

Note, that a lot off C & D's I have tried to clear up over the last few 
months, but I'm still working through them.

>
> Pros and Cons of shorter ways.

Some of the PGS imports have created very short ways (I've come across whole 
km of coastline made up of many 2 or 3 node ways)

In general when I've been tidying coastlines I've tried to join any sections 
of coastline less than 40 nodes.

Similarly I've come across some very long ways. In general (and its a 
personal view which I don't always adhere to myself) I don't like ways which 
are longer than 1,000 nodes.

>
> Does direction matter?

YES YES YES.  Coastline ways MUST be drawn with the water to the right.

>
> How often is coastline data updated?

Do you mean, "how often is the coastline file used to render the coast on 
the Mapnik layer" updated.  The answer is periodically, but generally every 
4 - 6 weeks

David


>
> Hope I keep every bodies feet dry and I don't damage something and find
> out next month that I messed up big time.
>
> Or don't bother "we" are working on that :-)
>
>
> Andrew
> aka Purple Mustang.
>
>
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