[OSM-dev] Finding water vs. land

Frederik Ramm frederik at remote.org
Sat May 9 17:50:56 BST 2009


Tels wrote:
> This works fine, except for coastlines, where I have two problems:

You're having exactly the same problems as the tiles at home project. The 
project has solved them by artificially closing the coastlines to form 
an ocean polygon. The mechanism to do it is in close-areas.pl if you 
care to have a look.

> * The coastlines are just open lines, but I need closed areas for 
> rendering

Water is always on the right, so the direction of the coastlines is 
important for you.

> * When I download data in the middle of the ocean, no coastline crosses 
> the tile and I do not know that the current tile must be filled 
> completely with water

You need to either download larger areas, or build an index that tells 
you which tile is "blue" and which "white".

> * get a complete, closed coast line (possible for the entire world?)
> and both best via some HTTP request :)

A closed coastline for the entire world would probably be between 100 MB 
and 1 GB of data. Sure you want that?


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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