[OSM-talk] Coastlines

Immanuel Scholz immanuel.scholz at gmx.de
Wed Mar 22 09:29:47 GMT 2006


> And it would be great if I don't have to download from 1000 different
> sources to get all the Data needed to draw a complete map.

I'm sorry, I used the wrong words.

I don't want to force the users to download from different sources too.
But the server can ;-).

As example, background tiles currently aren't hosted on the OSM server.
They are fetched on demand from a WMS server. My idea was, that other
people host the coastline database (because they have better data formats
to do so) and the server only imports rendered pictures or maybe read-only
vector data of the required area.

But if the coastline accuracy data isn't good enough, it may be better to
completly import it into OSM format so that people can start correcting
it. I still think we should seperate the database for this and the real
street data in the long term..

> I don't see any obvious reason why the current Data structure cannot
> easily hold coastlines, river lines and city boarders besides pure street
> information.

The main difference of coastlines is, that they are stored and transfered
in a way where the precision of the data increases with the detail level
you require.

This means if you want the coastline of, say, whole australia at once, you
may get only about 200 line segments. If you want the coastline of sydney
you also get 200 line segments but more detailed (this 200 lines may
represent just one line from the overall picture)

OSM data could reproduce this data transfer scheme only with additional
effort, which would complicate the current data scheme without gain.

On the other hand... maybe we find such a data representation to be
usefull for our data too. ;-)

Ciao, Imi.

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