[OSM-dev] Blue sea for tiles at home

Lars Aronsson lars at aronsson.se
Tue Apr 24 03:22:00 BST 2007

Frederik Ramm wrote:

> * If the tile being rendered has no "natural=coastline" ways, then
>    look up the tile coordinates in a table (which is supplied as a
>    4 MB binary file covering every single level-12 tile in the world,
>    thanks to Martijn for providing it!).
>    o If the table says there should be water at this location, then
>      draw an artificial "coastline" rectangle so that the tile gets
>      rendered blue.

When it works, it looks great.  But there are many places where it 
doesn't quite work.  Perhaps this is because of bad data, e.g. 
line segments pointing in the wrong direction, or coast lines 
being broken.

Would it be a terribly bad idea to inject these datapoints into 
the OSM database, i.e. nodes with water=yes or water=no, or 
something like that? If you do this, then anybody can correct 
errors by editing the attribute of that node.  We could even 
clarify by adding more such points at the middle of islands and 
lakes.  Instead of a special lookup in that table, the information 
would come as part of the normal API request.

  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se

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