[OSM-dev] coastline polygons

[Artem Pavlenko]

Hi Frederik,

> I haven't followed your efforts closely until now, and haven't fully
> understood what is going on. I have no idea what "LineStrings" are,
> and have never used mapnik. However it seems clear that you are
> somehow storing coastline data outside of the OSM database, and then
> linking it in when rendering tiles.

Yes, I store data in postgresql and also export to shapefiles. Mapnik can read 
both.  Why don't you try Mapnik? 
> Is this because keeping the coastline data in OSM poses a volume/
> performance problem, and how does it relate to the various "almien"
> coastline imports we are seeing already?

The main reason for storing data separately is to make use of spatial analisys 
tools (e.g JUMP). For the south-east of the UK I used original Shoreline data 
and 'almien' coastlines from OSM planet. I found coastlines in OSM to have  
lots of 'unclean' (e.g. self-intersecting)  geometries, probably because they 
went through some line simplification algorithms I don't know... 
  
> I would be very much in favour of coastline being stored in OSM
> because that would make them editable for everyone without special
> (non-OSM) tools.
>
Me too. But it would make sense to have something to start with, IMHO

Cheers,
Artem

> Bye
> Frederik