[OSM-talk] Slippy map - Mapnik layer UK coastlines

David Groom reviews at pacific-rim.net
Fri Mar 23 17:10:48 GMT 2007


----- Original Message ----- 
  From: Artem Pavlenko 
  To: David Groom 
  Cc: talk at openstreetmap.org 
  Sent: Friday, March 23, 2007 1:48 PM
  Subject: Re: [OSM-talk] Slippy map - Mapnik layer UK coastlines


  Hi David, 


  On 23 Mar 2007, at 11:48, David Groom wrote:


    It seems that the UK coastline is beginning to render better in the Mapnik 
    layer of the slippy map (it's a solid blue fill, rather than the odd shaped 
    grey polygons).


    However it does appear that the source for the coastline might be a rather 
    out of date planet file.


    In some places, eg 
    http://www.openstreetmap.org/index.html?lat=50.85383936185782&lon=-1.315713476905844&zoom=15 
    ,there is an exact correlation between coastline which is shown in the 
    Mapnik and Osmarender layers.


    In other places eg , 
    http://www.openstreetmap.org/index.html?lat=50.81094579389664&lon=-0.09869895092239864&zoom=15 
    ,the coastline outline in the Osmarender layer seems to be much more recent 
    than the Mapnik layer.




  For most of the world I was using original shoreline data, hence it's not as smooth as it should. Polygons are only available for England and Wales, the rest gets blue shoreline lines.  To have proper polygons for the whole planet :


  1. We need to agree that storing countries boundaries as polygons is way forward.


  2. We have to decide if storing these polygons in main OSM database is a good idea or not. I personally think it'll be better to store them separately. 


  3. Start creating polygons. I have all the tools and I'm happy to help anyone, but it is a big task which requires community participation.
   On the other hand, If one person capable of fixing most of the UK coastline it should be peanuts for OSM as a whole. If you want to see nice blue sea and land just do it, don't wait!


   Cheers,
  Artem


    David 






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  Artem Pavlenko
  http://mapnik.org






My original query remains, since both areas I was referring to are in the UK, about 70km away from each other.

I  can see advantages and disadvantages to storing polygons in the main OSM database.  One disadvantage I guess is it will dramatically increase the amount of data in the database, but I presume it would have the advantage that the polygons can be edited / amended using the usual OSM tools, so that alterations could be made by people with local knowledge.

Once 1) & 2) are agreed I'd be happy to assist if I can.

David
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